Add orx-keyframer

2020-04-07 14:28:09 +02:00
parent abde3fbe41
commit 8714b47102
27 changed files with 1807 additions and 0 deletions
--- a/orx-keyframer/README.md
+++ b/orx-keyframer/README.md
@@ -0,0 +1,99 @@
+# orx-keyframer
+
+A highly reusable keyframer.
+
+This POC relies on JSON files, but that's not a hard dependency, it can be replaced with any deserializer scheme.
+
+What this allows you to do:
+
+1. Create a keyframed animation in a json file.
+
+```json
+[
+  {
+    "time": 0.0,
+    "easing": "cubic-in-out",
+    "x": 3.0,
+    "y": 4.0,
+    "z": 9.0,
+    "r": 0.1,
+    "g": 0.5,
+    "b": 0.2,
+    "radius": 50
+  },
+  {
+    "time": 2.0,
+    "easing": "cubic-in-out",
+    "r": 0.6,
+    "g": 0.5,
+    "b": 0.1
+  },
+  {
+    "time": 4.0,
+    "easing": "cubic-in-out",
+    "x": 10.0,
+    "y": 4.0,
+    "radius": 400
+  },
+  {
+    "time": 5.0,
+    "easing": "cubic-in-out",
+    "x": 100.0,
+    "y": 320.0,
+    "radius": 400
+  },
+  {
+    "time": 5.3,
+    "easing": "cubic-in-out",
+    "x": 100.0,
+    "y": 320.0,
+    "radius": 40
+  }
+]
+```
+
+2. Map the animation data to Kotlin types:
+
+```kotlin
+class Animation : Keyframer() {
+    val position by Vector2Channel(arrayOf("x", "y"))
+    val radius by DoubleChannel("radius")
+    val color by RGBChannel(arrayOf("r", "g", "b"))
+}
+
+val animation = Animation()
+animation.loadFromJson(File("data/keyframes/animation.json"))
+```
+
+3. Animate! (from an OPENRNDR program)
+
+```kotlin
+extend {
+    animation(seconds)
+    drawer.fill = animation.color
+    drawer.circle(animation.position, animation.radius)
+}
+```
+
+## Advanced features
+
+orx-keyframer uses two file formats. A `SIMPLE` format and a `FULL` format. For reference check the [example full format .json](src/demo/resources/demo-full-01.json) and the [example program](src/demo/kotlin/DemoFull01.kt).
+The full format adds a `parameters` block and a `prototypes` block.
+
+[Repeats](src/demo/resources/demo-simple-repetitions-01.json), simple key repeating mechanism
+
+[Expressions](src/demo/resources/demo-simple-expressions-01.json), expression mechanism. Currently uses values `r` to indicate repeat index and `t` the last used key time, `v` the last used value (for the animated attribute).
+
+Supported functions in expressions:
+ - `min(x, y)`, `max(x, y)`
+ - `cos(x)`, `sin(x)`, `acos(x)`, `asin(x)`, `tan(x)`, `atan(x)`, `atan2(y, x)`
+ - `abs(x)`, `saturate(x)`
+ - `degrees(x)`, `radians(x)`
+ - `pow(x,y)`, `sqrt(x)`, `exp(x)`
+ - `mix(left, right, x)`
+ - `smoothstep(t0, t1, x)`
+ - `map(leftBefore, rightBefore, leftAfter, rightAfter, x)`
+ - `random()`, `random(min, max)`
+  
+[Parameters and prototypes](src/demo/resources/demo-full-01.json)
+
--- a/orx-keyframer/build.gradle
+++ b/orx-keyframer/build.gradle
@@ -0,0 +1,47 @@
+//plugins {
+//    id 'antlr'
+//}
+
+apply plugin: 'antlr'
+
+sourceSets {
+    demo {
+        java {
+            srcDirs = ["src/demo/kotlin"]
+            compileClasspath += main.getCompileClasspath()
+            runtimeClasspath += main.getRuntimeClasspath()
+        }
+    }
+    main {
+        java {
+            srcDir("src/main/java")
+            srcDir("src/main/kotlin")
+            srcDir("build/generated-src/antlr")
+        }
+    }
+}
+
+
+
+generateGrammarSource {
+    maxHeapSize = "64m"
+    arguments += ["-visitor", "-long-messages"]
+    outputDirectory = file("${project.buildDir}/generated-src/antlr/org/openrndr/extra/keyframer/antlr".toString())
+
+}
+
+dependencies {
+    antlr("org.antlr:antlr4:$antlrVersion")
+    implementation("org.antlr:antlr4-runtime:$antlrVersion")
+    implementation(project(":orx-noise"))
+    implementation(project(":orx-easing"))
+    implementation "com.google.code.gson:gson:$gsonVersion"
+    implementation("org.jetbrains.kotlin:kotlin-reflect:$kotlinVersion")
+
+    demoImplementation(project(":orx-camera"))
+    demoImplementation(project(":orx-panel"))
+    demoImplementation("org.openrndr:openrndr-core:$openrndrVersion")
+    demoRuntimeOnly("org.openrndr:openrndr-gl3:$openrndrVersion")
+    demoRuntimeOnly("org.openrndr:openrndr-gl3-natives-$openrndrOS:$openrndrVersion")
+    demoImplementation(sourceSets.getByName("main").output)
+}
--- a/orx-keyframer/src/demo/kotlin/DemoFull01.kt
+++ b/orx-keyframer/src/demo/kotlin/DemoFull01.kt
@@ -0,0 +1,23 @@
+import org.openrndr.application
+import org.openrndr.extra.keyframer.Keyframer
+import org.openrndr.extra.keyframer.KeyframerFormat
+import org.openrndr.resourceUrl
+import java.net.URL
+
+fun main() = application {
+    program {
+        class Animation: Keyframer() {
+            val position by Vector2Channel(arrayOf("x", "y"))
+            val radius by DoubleChannel("radius")
+            val color by RGBChannel(arrayOf("r", "g", "b"))
+        }
+        val animation = Animation()
+        animation.loadFromJson(URL(resourceUrl("/demo-full-01.json")), format = KeyframerFormat.FULL)
+
+        extend {
+            animation(seconds)
+            drawer.fill = animation.color
+            drawer.circle(animation.position, animation.radius)
+        }
+    }
+}
--- a/orx-keyframer/src/demo/kotlin/DemoScrub01.kt
+++ b/orx-keyframer/src/demo/kotlin/DemoScrub01.kt
@@ -0,0 +1,47 @@
+import org.openrndr.application
+import org.openrndr.extra.keyframer.Keyframer
+import org.openrndr.panel.controlManager
+import org.openrndr.panel.elements.Range
+import org.openrndr.panel.elements.Slider
+import org.openrndr.panel.elements.slider
+import org.openrndr.resourceUrl
+import java.net.URL
+
+fun main() = application {
+    program {
+
+        // -- replace the default clock with an offset clock
+        var clockOffset = 0.0
+        val oldClock = clock
+        clock = { oldClock() - clockOffset }
+        var clockSlider: Slider? = null
+
+        // -- setup a simple UI
+        val cm = controlManager {
+            layout {
+                clockSlider = slider {
+                    range = Range(0.0, 30.0)
+                    events.valueChanged.listen {
+                        if (it.interactive) {
+                            clockOffset = oldClock() - it.newValue
+                        }
+                    }
+                }
+            }
+        }
+        extend(cm)
+
+        class Animation: Keyframer() {
+            val position by Vector2Channel(arrayOf("x", "y"))
+        }
+        val animation = Animation()
+        animation.loadFromJson(URL(resourceUrl("/demo-simple-01.json")))
+
+        extend {
+            // -- update the slider
+            clockSlider?.value = seconds
+            animation(seconds)
+            drawer.circle(animation.position, 100.0)
+        }
+    }
+}
--- a/orx-keyframer/src/demo/kotlin/DemoSimple01.kt
+++ b/orx-keyframer/src/demo/kotlin/DemoSimple01.kt
@@ -0,0 +1,19 @@
+import org.openrndr.application
+import org.openrndr.extra.keyframer.Keyframer
+import org.openrndr.resourceUrl
+import java.net.URL
+
+fun main() = application {
+    program {
+        class Animation: Keyframer() {
+            val position by Vector2Channel(arrayOf("x", "y"))
+        }
+        val animation = Animation()
+        animation.loadFromJson(URL(resourceUrl("/demo-simple-01.json")))
+
+        extend {
+            animation(seconds)
+            drawer.circle(animation.position, 100.0)
+        }
+    }
+}
--- a/orx-keyframer/src/demo/kotlin/DemoSimple02.kt
+++ b/orx-keyframer/src/demo/kotlin/DemoSimple02.kt
@@ -0,0 +1,21 @@
+import org.openrndr.application
+import org.openrndr.extra.keyframer.Keyframer
+import org.openrndr.resourceUrl
+import java.net.URL
+
+fun main() = application {
+    program {
+        class Animation: Keyframer() {
+            val position by Vector2Channel(arrayOf("x", "y"))
+            val radius by DoubleChannel("radius")
+            val color by RGBChannel(arrayOf("r", "g", "b"))
+        }
+        val animation = Animation()
+        animation.loadFromJson(URL(resourceUrl("/demo-simple-02.json")))
+        extend {
+            animation(seconds)
+            drawer.fill = animation.color
+            drawer.circle(animation.position, animation.radius)
+        }
+    }
+}
--- a/orx-keyframer/src/demo/kotlin/DemoSimpleExpressions01.kt
+++ b/orx-keyframer/src/demo/kotlin/DemoSimpleExpressions01.kt
@@ -0,0 +1,22 @@
+import org.openrndr.application
+import org.openrndr.extra.keyframer.Keyframer
+import org.openrndr.resourceUrl
+import java.net.URL
+
+fun main() = application {
+    program {
+        class Animation : Keyframer() {
+            val position by Vector2Channel(arrayOf("x", "y"))
+            val radius by DoubleChannel("x")
+        }
+
+        val animation = Animation()
+        animation.loadFromJson(URL(resourceUrl("/demo-simple-expressions-01.json")),
+                parameters = mapOf("cycleDuration" to 2.0))
+
+        extend {
+            animation(seconds)
+            drawer.circle(animation.position, animation.radius)
+        }
+    }
+}
--- a/orx-keyframer/src/demo/kotlin/DemoSimpleRepetitions01.kt
+++ b/orx-keyframer/src/demo/kotlin/DemoSimpleRepetitions01.kt
@@ -0,0 +1,20 @@
+import org.openrndr.application
+import org.openrndr.extra.keyframer.Keyframer
+import org.openrndr.resourceUrl
+import java.net.URL
+
+fun main() = application {
+    program {
+        class Animation: Keyframer() {
+            val position by Vector2Channel(arrayOf("x", "y"))
+            val radius by DoubleChannel("x")
+        }
+        val animation = Animation()
+        animation.loadFromJson(URL(resourceUrl("/demo-simple-repetitions-01.json")))
+
+        extend {
+            animation(seconds)
+            drawer.circle(animation.position, animation.radius)
+        }
+    }
+}
--- a/orx-keyframer/src/demo/resources/demo-full-01.json
+++ b/orx-keyframer/src/demo/resources/demo-full-01.json
@@ -0,0 +1,74 @@
+{
+  // this is breaking with proper json but.. gson accepts comments and they are invaluable
+  // in the parameters block you can add custom values, which can be used in expressions
+  "parameters": {
+    "smallRadius": 5.0,
+    "repetitionCount": 10,
+    "width": 640.0,
+    "height": 480.0,
+    // you can have expressions inside parameters too, they are evaluated once, on load
+    "resolvedOnLoad" : "width * 2.0"
+  },
+  // in the prototypes you can set up key prototypes
+  "prototypes": {
+    "red": {
+      "r": 1.0,
+      "g": 0.0,
+      "b": 0.0
+    },
+    "blue": {
+      "r": 0.0,
+      "g": 0.0,
+      "b": 1.0
+    },
+    "center": {
+      // prototypes can have expressions too, they are evaluated as late as possible
+      // thus, they are evaluated more than once
+      "x": "width / 2",
+      "y": "height / 2"
+    },
+    "small": {
+      "radius": "smallRadius"
+    },
+    "large": {
+      "radius": "smallRadius * 10.0"
+    }
+  },
+  "keys": [
+    {
+      "time": 0.0,
+      "easing": "cubic-in-out",
+      "x": 3.0,
+      "y": 4.0,
+      "z": 9.0,
+      "r": 0.0,
+      "g": 1.0,
+      "b": 0.0,
+      "radius": 50,
+      "foo" : 0.0
+    },
+    {
+      "time": 2.0,
+      "easing": "cubic-in-out",
+      // here we apply the prototypes in cascading fashion from left to right
+      "prototypes": "red center small"
+    },
+    {
+      "time": 3.0,
+      "repeat": {
+        "count": "repetitionCount",
+        "keys": [
+          {
+            "time": "(rep * 2.0) + 3.0",
+            "prototypes": "blue large",
+            "easing": "cubic-in-out"
+          },
+          {
+            "time": "t + 1.0",
+            "prototypes": "red small"
+          }
+        ]
+      }
+    }
+  ]
+}
--- a/orx-keyframer/src/demo/resources/demo-simple-01.json
+++ b/orx-keyframer/src/demo/resources/demo-simple-01.json
@@ -0,0 +1,20 @@
+[
+  {
+    "time": 0.0,
+    "x": 320.0,
+    "y": 240.0
+  },
+  {
+    "time": 10.0,
+    "x": 0.0,
+    "y": 0.0,
+    "easing": "cubic-in-out"
+  },
+  {
+    "time": 20.0,
+    "x": 640.0,
+    "y": 480.0,
+    "easing": "cubic-in-out"
+  }
+
+]
--- a/orx-keyframer/src/demo/resources/demo-simple-02.json
+++ b/orx-keyframer/src/demo/resources/demo-simple-02.json
@@ -0,0 +1,32 @@
+[
+  {
+    "time": 0.0,
+    "x": 320.0,
+    "y": 240.0,
+    "radius": 0.0,
+    "r": 1.0,
+    "g": 1.0,
+    "b": 1.0
+  },
+  {
+    "time": 5.0,
+    "radius": 200.0,
+    "r": 0.0
+  },
+  {
+    "time": 10.0,
+    "g": 0.0,
+    "x": 0.0,
+    "y": 0.0,
+    "easing": "cubic-in-out"
+  },
+  {
+    "time": 20.0,
+    "x": 640.0,
+    "y": 480.0,
+    "radius": 50.0,
+    "easing": "cubic-in-out",
+    "g": 1.0,
+    "b": 0.0
+  }
+]
--- a/orx-keyframer/src/demo/resources/demo-simple-expressions-01.json
+++ b/orx-keyframer/src/demo/resources/demo-simple-expressions-01.json
@@ -0,0 +1,30 @@
+[
+  {
+    "time": 0.0,
+    "x": 320.0,
+    "y": 240.0,
+    "radius": 0.0
+  },
+  {
+    "time": 3.0,
+    "repeat": {
+      "count": 5,
+      "keys": [
+        {
+          "duration": "cycleDuration * 0.5",
+          "easing": "cubic-in-out",
+          "x": 10.0,
+          "y": 4.0,
+          "radius": 400
+        },
+        {
+          "duration": "cycleDuration * 0.5",
+          "easing": "cubic-in-out",
+          "x": 630.0,
+          "y": 470.0,
+          "radius": 40
+        }
+      ]
+    }
+  }
+]
--- a/orx-keyframer/src/demo/resources/demo-simple-repetitions-01.json
+++ b/orx-keyframer/src/demo/resources/demo-simple-repetitions-01.json
@@ -0,0 +1,30 @@
+[
+  {
+    "time": 0.0,
+    "x": 320.0,
+    "y": 240.0,
+    "radius": 0.0
+  },
+  {
+    "time": 3.0,
+    "repeat": {
+      "count": 5,
+      "keys": [
+        {
+          "duration": 1.0,
+          "easing": "cubic-in-out",
+          "x": 10.0,
+          "y": 4.0,
+          "radius": 400
+        },
+        {
+          "duration": 1.0,
+          "easing": "cubic-in-out",
+          "x": 630.0,
+          "y": 470.0,
+          "radius": 40
+        }
+      ]
+    }
+  }
+]
--- a/orx-keyframer/src/main/antlr/KeyLangLexer.g4
+++ b/orx-keyframer/src/main/antlr/KeyLangLexer.g4
@@ -0,0 +1,90 @@
+lexer grammar KeyLangLexer;
+
+@header {
+package org.openrndr.extra.keyframer.antlr;
+}
+
+channels { WHITESPACE }
+
+// Whitespace
+NEWLINE            : '\r\n' | '\r' | '\n' ;
+WS                 : [\t ]+ -> channel(WHITESPACE) ;
+
+// Keywords
+INPUT              : 'input' ;
+VAR                : 'var' ;
+PRINT              : 'print';
+AS                 : 'as';
+INT                : 'Int';
+DECIMAL            : 'Decimal';
+STRING             : 'String';
+
+// Identifiers
+ID                 : [_]*[a-zA-Z][A-Za-z0-9_]* ;
+FUNCTION_ID        : [_]*[a-z][A-Za-z0-9_]* ;
+
+// Literals
+
+DECLIT             : [0-9][0-9]* '.' [0-9]+ ;
+INTLIT             : '0'|[0-9][0-9]* ;
+
+// Operators
+PLUS               : '+' ;
+PERCENTAGE         : '%' ;
+MINUS              : '-' ;
+ASTERISK           : '*' ;
+DIVISION           : '/' ;
+ASSIGN             : '=' ;
+LPAREN             : '(' ;
+RPAREN             : ')' ;
+
+COMMA              : ',' ;
+
+STRING_OPEN        : '"' -> pushMode(MODE_IN_STRING);
+
+UNMATCHED          : . ;
+
+mode MODE_IN_STRING;
+
+ESCAPE_STRING_DELIMITER : '\\"' ;
+ESCAPE_SLASH            : '\\\\' ;
+ESCAPE_NEWLINE          : '\\n' ;
+ESCAPE_SHARP            : '\\#' ;
+STRING_CLOSE            : '"' -> popMode ;
+INTERPOLATION_OPEN      : '#{' -> pushMode(MODE_IN_INTERPOLATION) ;
+STRING_CONTENT          : ~["\n\r\t\\#]+ ;
+
+STR_UNMATCHED           : . -> type(UNMATCHED) ;
+
+mode MODE_IN_INTERPOLATION;
+
+INTERPOLATION_CLOSE       : '}' -> popMode ;
+
+INTERP_WS                 : [\t ]+ -> channel(WHITESPACE), type(WS) ;
+
+// Keywords
+INTERP_AS                 : 'as'-> type(AS) ;
+INTERP_INT                : 'Int'-> type(INT) ;
+INTERP_DECIMAL            : 'Decimal'-> type(DECIMAL) ;
+INTERP_STRING             : 'String'-> type(STRING) ;
+
+// Literals
+INTERP_INTLIT             : ('0'|[1-9][0-9]*) -> type(INTLIT) ;
+INTERP_DECLIT             : ('0'|[1-9][0-9]*) '.' [0-9]+ -> type(DECLIT) ;
+
+// Operators
+INTERP_PLUS               : '+' -> type(PLUS) ;
+INTERP_MINUS              : '-' -> type(MINUS) ;
+INTERP_ASTERISK           : '*' -> type(ASTERISK) ;
+INTERP_DIVISION           : '/' -> type(DIVISION) ;
+INTERP_PERCENTAGE           : '%' -> type(PERCENTAGE) ;
+INTERP_ASSIGN             : '=' -> type(ASSIGN) ;
+INTERP_LPAREN             : '(' -> type(LPAREN) ;
+INTERP_RPAREN             : ')' -> type(RPAREN) ;
+
+// Identifiers
+INTERP_ID                 : [_]*[a-z][A-Za-z0-9_]* -> type(ID);
+
+INTERP_STRING_OPEN        : '"' -> type(STRING_OPEN), pushMode(MODE_IN_STRING);
+
+INTERP_UNMATCHED          : . -> type(UNMATCHED) ;
--- a/orx-keyframer/src/main/antlr/KeyLangParser.g4
+++ b/orx-keyframer/src/main/antlr/KeyLangParser.g4
@@ -0,0 +1,46 @@
+
+parser grammar KeyLangParser;
+
+@header {
+package org.openrndr.extra.keyframer.antlr;
+}
+
+options { tokenVocab=KeyLangLexer; }
+
+miniCalcFile : lines=line+ ;
+
+line      : statement (NEWLINE | EOF) ;
+
+statement : inputDeclaration # inputDeclarationStatement
+          | varDeclaration   # varDeclarationStatement
+          | assignment       # assignmentStatement
+          | print            # printStatement
+          | expression       # expressionStatement ;
+
+print : PRINT LPAREN expression RPAREN ;
+
+inputDeclaration : INPUT type name=ID ;
+
+varDeclaration : VAR assignment ;
+
+assignment : ID ASSIGN expression ;
+
+expression : INTLIT                                                        # intLiteral
+           | DECLIT                                                        # decimalLiteral
+           | ID LPAREN RPAREN                                              # functionCall0Expression
+           | ID LPAREN expression RPAREN                                   # functionCall1Expression
+           | ID LPAREN expression COMMA expression RPAREN                  # functionCall2Expression
+           | ID LPAREN expression COMMA expression COMMA expression RPAREN # functionCall3Expression
+           | ID LPAREN expression COMMA expression COMMA expression COMMA expression RPAREN # functionCall4Expression
+           | ID LPAREN expression COMMA expression COMMA expression COMMA expression COMMA expression RPAREN # functionCall5Expression
+           | ID                                                            # valueReference
+           | LPAREN expression RPAREN                                      # parenExpression
+           | MINUS expression                                              # minusExpression
+           | expression operator=(DIVISION|ASTERISK|PERCENTAGE) expression # binaryOperation1
+           | expression operator=(PLUS|MINUS) expression        # binaryOperation2;
+
+type : DECIMAL # decimal
+     | INT     # integer
+     | STRING  # string ;
+
+
--- a/orx-keyframer/src/main/kotlin/Expressions.kt
+++ b/orx-keyframer/src/main/kotlin/Expressions.kt
@@ -0,0 +1,398 @@
+package org.openrndr.extra.keyframer
+
+import org.antlr.v4.runtime.*
+import org.antlr.v4.runtime.tree.ParseTreeWalker
+import org.antlr.v4.runtime.tree.TerminalNode
+import org.openrndr.extra.keyframer.antlr.*
+import org.openrndr.extra.noise.uniform
+import org.openrndr.math.map
+import org.openrndr.math.mix
+import org.openrndr.math.mod
+import org.openrndr.math.smoothstep
+import java.util.*
+import kotlin.math.*
+
+typealias Function0 = () -> Double
+typealias Function1 = (Double) -> Double
+typealias Function2 = (Double, Double) -> Double
+typealias Function3 = (Double, Double, Double) -> Double
+typealias Function4 = (Double, Double, Double, Double) -> Double
+typealias Function5 = (Double, Double, Double, Double, Double) -> Double
+
+class FunctionExtensions(
+    val functions0: Map<String, Function0> = emptyMap(),
+    val functions1: Map<String, Function1> = emptyMap(),
+    val functions2: Map<String, Function2> = emptyMap(),
+    val functions3: Map<String, Function3> = emptyMap(),
+    val functions4: Map<String, Function4> = emptyMap(),
+    val functions5: Map<String, Function5> = emptyMap()
+) {
+    companion object {
+        val EMPTY = FunctionExtensions()
+    }
+}
+
+internal enum class IDType {
+    VARIABLE,
+    FUNCTION0,
+    FUNCTION1,
+    FUNCTION2,
+    FUNCTION3,
+    FUNCTION4,
+    FUNCTION5
+}
+
+internal class ExpressionListener(val functions: FunctionExtensions = FunctionExtensions.EMPTY) :
+    KeyLangParserBaseListener() {
+    val doubleStack = Stack<Double>()
+    val functionStack = Stack<(DoubleArray) -> Double>()
+    val variables = mutableMapOf<String, Double>()
+
+    val idTypeStack = Stack<IDType>()
+    var lastExpressionResult: Double? = null
+
+    val exceptionStack = Stack<ExpressionException>()
+
+
+    override fun exitExpressionStatement(ctx: KeyLangParser.ExpressionStatementContext) {
+        ifError {
+            throw ExpressionException("error in evaluation of '${ctx.text}': ${it.message ?: ""}")
+        }
+        val result = doubleStack.pop()
+        lastExpressionResult = result
+    }
+
+    override fun exitAssignment(ctx: KeyLangParser.AssignmentContext) {
+        val value = doubleStack.pop()
+        variables[ctx.ID()?.text ?: error("buh")] = value
+    }
+
+    override fun exitMinusExpression(ctx: KeyLangParser.MinusExpressionContext) {
+        super.exitMinusExpression(ctx)
+    }
+
+    override fun exitBinaryOperation1(ctx: KeyLangParser.BinaryOperation1Context) {
+        ifError {
+            pushError(it.message ?: "")
+            return
+        }
+
+        val right = doubleStack.pop()
+        val left = doubleStack.pop()
+        val result = when (val operator = ctx.operator?.type) {
+            KeyLangParser.PLUS -> left + right
+            KeyLangParser.MINUS -> left - right
+            KeyLangParser.ASTERISK -> left * right
+            KeyLangParser.DIVISION -> left / right
+            KeyLangParser.PERCENTAGE -> mod(left, right)
+            else -> error("operator '$operator' not implemented")
+        }
+        doubleStack.push(result)
+    }
+
+    override fun exitBinaryOperation2(ctx: KeyLangParser.BinaryOperation2Context) {
+        ifError {
+            pushError(it.message ?: "")
+            return
+        }
+
+        val left = doubleStack.pop()
+        val right = doubleStack.pop()
+        val result = when (val operator = ctx.operator?.type) {
+            KeyLangParser.PLUS -> left + right
+            KeyLangParser.MINUS -> right - left
+            KeyLangParser.ASTERISK -> left * right
+            KeyLangParser.DIVISION -> left / right
+            else -> error("operator '$operator' not implemented")
+        }
+        doubleStack.push(result)
+    }
+
+    override fun enterValueReference(ctx: KeyLangParser.ValueReferenceContext) {
+        idTypeStack.push(IDType.VARIABLE)
+    }
+
+    override fun enterFunctionCall0Expression(ctx: KeyLangParser.FunctionCall0ExpressionContext) {
+        idTypeStack.push(IDType.FUNCTION0)
+    }
+
+    override fun exitFunctionCall0Expression(ctx: KeyLangParser.FunctionCall0ExpressionContext) {
+        ifError {
+            pushError(it.message ?: "")
+            return
+        }
+
+        val function = functionStack.pop()
+        val result = function.invoke(doubleArrayOf())
+        doubleStack.push(result)
+    }
+
+    override fun enterFunctionCall1Expression(ctx: KeyLangParser.FunctionCall1ExpressionContext) {
+        idTypeStack.push(IDType.FUNCTION1)
+    }
+
+    override fun exitFunctionCall1Expression(ctx: KeyLangParser.FunctionCall1ExpressionContext) {
+        ifError {
+            pushError(it.message ?: "")
+            return
+        }
+
+        val function = functionStack.pop()
+        val argument = doubleStack.pop()
+
+        val result = function.invoke(doubleArrayOf(argument))
+        doubleStack.push(result)
+    }
+
+    override fun enterFunctionCall2Expression(ctx: KeyLangParser.FunctionCall2ExpressionContext) {
+        idTypeStack.push(IDType.FUNCTION2)
+    }
+
+    override fun exitFunctionCall2Expression(ctx: KeyLangParser.FunctionCall2ExpressionContext) {
+        ifError {
+            pushError(it.message ?: "")
+            return
+        }
+
+        val function = functionStack.pop()
+        val argument1 = doubleStack.pop()
+        val argument0 = doubleStack.pop()
+
+        val result = function.invoke(doubleArrayOf(argument0, argument1))
+        doubleStack.push(result)
+    }
+
+    override fun enterFunctionCall3Expression(ctx: KeyLangParser.FunctionCall3ExpressionContext) {
+        idTypeStack.push(IDType.FUNCTION3)
+    }
+
+    override fun exitFunctionCall3Expression(ctx: KeyLangParser.FunctionCall3ExpressionContext) {
+        ifError {
+            pushError(it.message ?: "")
+            return
+        }
+
+        val function = functionStack.pop()
+        val argument2 = doubleStack.pop()
+        val argument1 = doubleStack.pop()
+        val argument0 = doubleStack.pop()
+
+        val result = function.invoke(doubleArrayOf(argument0, argument1, argument2))
+        doubleStack.push(result)
+    }
+
+    override fun enterFunctionCall4Expression(ctx: KeyLangParser.FunctionCall4ExpressionContext) {
+        idTypeStack.push(IDType.FUNCTION4)
+    }
+
+    override fun exitFunctionCall4Expression(ctx: KeyLangParser.FunctionCall4ExpressionContext) {
+        ifError {
+            pushError(it.message ?: "")
+            return
+        }
+
+        val function = functionStack.pop()
+        val argument3 = doubleStack.pop()
+        val argument2 = doubleStack.pop()
+        val argument1 = doubleStack.pop()
+        val argument0 = doubleStack.pop()
+
+        val result = function.invoke(doubleArrayOf(argument0, argument1, argument2, argument3))
+        doubleStack.push(result)
+    }
+
+
+    override fun enterFunctionCall5Expression(ctx: KeyLangParser.FunctionCall5ExpressionContext) {
+        idTypeStack.push(IDType.FUNCTION5)
+    }
+
+    override fun exitFunctionCall5Expression(ctx: KeyLangParser.FunctionCall5ExpressionContext) {
+        ifError {
+            pushError(it.message ?: "")
+            return
+        }
+
+        val function = functionStack.pop()
+        val argument4 = doubleStack.pop()
+        val argument3 = doubleStack.pop()
+        val argument2 = doubleStack.pop()
+        val argument1 = doubleStack.pop()
+        val argument0 = doubleStack.pop()
+
+        val result = function.invoke(doubleArrayOf(argument0, argument1, argument2, argument3, argument4))
+        doubleStack.push(result)
+    }
+
+    private fun <T> errorValue(message: String, value: T): T {
+        pushError(message)
+        return value
+    }
+
+    private fun pushError(message: String) {
+        exceptionStack.push(ExpressionException(message))
+    }
+
+    private inline fun ifError(f: (e: Throwable) -> Unit) {
+        if (exceptionStack.isNotEmpty()) {
+            val e = exceptionStack.pop()
+            f(e)
+        }
+    }
+
+    override fun visitTerminal(node: TerminalNode) {
+        val type = node.symbol?.type
+        if (type == KeyLangParser.INTLIT) {
+            doubleStack.push(node.text.toDouble())
+        }
+        if (type == KeyLangParser.DECLIT) {
+            doubleStack.push(node.text.toDouble())
+        }
+        if (type == KeyLangParser.ID) {
+
+            @Suppress("DIVISION_BY_ZERO")
+            when (val idType = idTypeStack.pop()) {
+                IDType.VARIABLE -> doubleStack.push(
+                    when (val name = node.text) {
+                        "PI" -> PI
+                        else -> variables[name] ?: errorValue("unresolved variable: '${name}'", 0.0 / 0.0)
+                    }
+                )
+
+                IDType.FUNCTION0 -> {
+                    val function: (DoubleArray) -> Double =
+                        when (val candidate = node.text) {
+                            "random" -> { _ -> Double.uniform(0.0, 1.0) }
+                            else -> functions.functions0[candidate]?.let { { _:DoubleArray -> it.invoke() } }
+                                ?: errorValue(
+                                    "unresolved function: '${candidate}()'"
+                                ) { _ -> error("this is the error function") }
+                        }
+                    functionStack.push(function)
+                }
+
+                IDType.FUNCTION1 -> {
+                    val function: (DoubleArray) -> Double =
+                        when (val candidate = node.text) {
+                            "sqrt" -> { x -> sqrt(x[0]) }
+                            "radians" -> { x -> Math.toRadians(x[0]) }
+                            "degrees" -> { x -> Math.toDegrees(x[0]) }
+                            "cos" -> { x -> cos(x[0]) }
+                            "sin" -> { x -> sin(x[0]) }
+                            "tan" -> { x -> tan(x[0]) }
+                            "atan" -> { x -> atan(x[0]) }
+                            "acos" -> { x -> acos(x[0]) }
+                            "asin" -> { x -> asin(x[0]) }
+                            "exp" -> { x -> exp(x[0]) }
+                            "abs" -> { x -> abs(x[0]) }
+                            "floor" -> { x -> floor(x[0]) }
+                            "ceil" -> { x -> ceil(x[0]) }
+                            "saturate" -> { x -> x[0].coerceIn(0.0, 1.0) }
+                            else -> functions.functions1[candidate]?.let { { x:DoubleArray -> it.invoke(x[0]) } }
+                                ?: errorValue(
+                                    "unresolved function: '${candidate}(x0)'"
+                                ) { _ -> error("this is the error function") }
+                        }
+                    functionStack.push(function)
+                }
+                IDType.FUNCTION2 -> {
+                    val function: (DoubleArray) -> Double =
+                        when (val candidate = node.text) {
+                            "max" -> { x -> max(x[0], x[1]) }
+                            "min" -> { x -> min(x[0], x[1]) }
+                            "pow" -> { x -> x[0].pow(x[1]) }
+                            "atan2" -> { x -> atan2(x[0], x[1]) }
+                            "random" -> { x -> Double.uniform(x[0], x[1]) }
+                            else -> functions.functions2[candidate]?.let { { x:DoubleArray -> it.invoke(x[0], x[1]) } }
+                                ?: errorValue(
+                                    "unresolved function: '${candidate}(x0, x1)'"
+                                ) { _ -> error("this is the error function") }
+                        }
+                    functionStack.push(function)
+                }
+                IDType.FUNCTION3 -> {
+                    val function: (DoubleArray) -> Double =
+                        when (val candidate = node.text) {
+                            "mix" -> { x -> mix(x[0], x[1], x[2]) }
+                            "smoothstep" -> { x -> smoothstep(x[0], x[1], x[2]) }
+                            else -> functions.functions3[candidate]?.let { { x:DoubleArray -> it.invoke(x[0], x[1], x[2]) } }
+                                ?: errorValue(
+                                    "unresolved function: '${candidate}(x0, x1, x2)'"
+                                ) { _ -> error("this is the error function") }
+                        }
+                    functionStack.push(function)
+                }
+                IDType.FUNCTION4 -> {
+                    val function: (DoubleArray) -> Double =
+                        when (val candidate = node.text) {
+                            else -> functions.functions4[candidate]?.let { { x:DoubleArray -> it.invoke(x[0], x[1], x[2], x[3]) } }
+                                ?: errorValue(
+                                    "unresolved function: '${candidate}(x0, x1, x2, x3)'"
+                                ) { _ -> error("this is the error function") }
+                        }
+                    functionStack.push(function)
+                }
+
+                IDType.FUNCTION5 -> {
+                    val function: (DoubleArray) -> Double =
+                        when (val candidate = node.text) {
+                            "map" -> { x -> map(x[0], x[1], x[2], x[3], x[4]) }
+                            else -> functions.functions5[candidate]?.let { { x:DoubleArray -> it.invoke(x[0], x[1], x[2], x[3], x[4]) } }
+                                ?: errorValue(
+                                    "unresolved function: '${candidate}(x0, x1, x2, x3, x4)'"
+                                ) { _ -> error("this is the error function") }
+                        }
+                    functionStack.push(function)
+                }
+                else -> error("unsupported id-type $idType")
+            }
+        }
+    }
+}
+
+class ExpressionException(message: String) : RuntimeException(message)
+
+fun evaluateExpression(
+    input: String,
+    variables: Map<String, Double> = emptyMap(),
+    functions: FunctionExtensions = FunctionExtensions.EMPTY
+): Double? {
+    val lexer = KeyLangLexer(CharStreams.fromString(input))
+//
+//    lexer.removeErrorListeners()
+//    lexer.addErrorListener(object : BaseErrorListener() {
+//        override fun syntaxError(
+//            recognizer: Recognizer<*, *>?,
+//            offendingSymbol: Any?,
+//            line: Int,
+//            charPositionInLine: Int,
+//            msg: String?,
+//            e: RecognitionException?
+//        ) {
+//            println("syntax error!")
+//        }
+//    })
+    val parser = KeyLangParser(CommonTokenStream(lexer))
+    parser.removeErrorListeners()
+    parser.addErrorListener(object : BaseErrorListener() {
+        override fun syntaxError(
+            recognizer: Recognizer<*, *>?,
+            offendingSymbol: Any?,
+            line: Int,
+            charPositionInLine: Int,
+            msg: String?,
+            e: RecognitionException?
+        ) {
+            throw ExpressionException("parser error in expression: '$input'; [line: $line, character: $charPositionInLine ${offendingSymbol?.let { ", near: $it" } ?: ""} ]")
+        }
+    })
+
+    val root = parser.miniCalcFile()
+    val listener = ExpressionListener(functions)
+    listener.variables.putAll(variables)
+    try {
+        ParseTreeWalker.DEFAULT.walk(listener, root)
+    } catch (e: ExpressionException) {
+        throw ExpressionException(e.message ?: "")
+    }
+    return listener.lastExpressionResult
+}
--- a/orx-keyframer/src/main/kotlin/Key.kt
+++ b/orx-keyframer/src/main/kotlin/Key.kt
@@ -0,0 +1,68 @@
+package org.openrndr.extra.keyframer
+
+import org.openrndr.extras.easing.Easing
+import org.openrndr.extras.easing.EasingFunction
+
+class Key(val time: Double, val value: Double, val easing: EasingFunction)
+
+enum class Hold {
+    HoldNone,
+    HoldSet,
+    HoldAll
+}
+
+class KeyframerChannel {
+    val keys = mutableListOf<Key>()
+
+    operator fun invoke() : Double {
+        return 0.0
+    }
+
+    fun add(time: Double, value: Double?, easing: EasingFunction = Easing.Linear.function, jump: Hold = Hold.HoldNone) {
+        if (jump == Hold.HoldAll || (jump == Hold.HoldSet && value != null)) {
+            lastValue()?.let {
+                keys.add(Key(time, it, Easing.Linear.function))
+            }
+        }
+        value?.let {
+            keys.add(Key(time, it, easing))
+        }
+    }
+
+    fun lastValue(): Double? {
+        return keys.lastOrNull()?.value
+    }
+
+    fun duration(): Double {
+        return keys.last().time
+    }
+
+    fun value(time: Double): Double? {
+        if (keys.size == 0) {
+            return null
+        }
+        if (keys.size == 1) {
+            return if (time < keys.first().time) {
+                null
+            } else {
+                keys[0].value
+            }
+        }
+
+        if (time < keys.first().time) {
+            return null
+        }
+
+        val rightIndex = keys.indexOfFirst { it.time > time }
+        return if (rightIndex == -1) {
+            keys.last().value
+        } else {
+            val leftIndex = (rightIndex - 1).coerceAtLeast(0)
+            val rightKey = keys[rightIndex]
+            val leftKey = keys[leftIndex]
+            val t0 = (time - leftKey.time) / (rightKey.time - leftKey.time)
+            val e0 = rightKey.easing(t0, 0.0, 1.0, 1.0)
+            leftKey.value * (1.0 - e0) + rightKey.value * (e0)
+        }
+    }
+}
--- a/orx-keyframer/src/main/kotlin/Keyframer.kt
+++ b/orx-keyframer/src/main/kotlin/Keyframer.kt
@@ -0,0 +1,375 @@
+package org.openrndr.extra.keyframer
+
+import com.google.gson.Gson
+import com.google.gson.JsonSyntaxException
+import com.google.gson.reflect.TypeToken
+import org.openrndr.color.ColorRGBa
+import org.openrndr.extras.easing.Easing
+import org.openrndr.math.Vector2
+import org.openrndr.math.Vector3
+import org.openrndr.math.Vector4
+import java.io.File
+import java.lang.IllegalStateException
+import java.net.URL
+import kotlin.math.roundToInt
+import kotlin.reflect.KProperty
+import kotlin.reflect.KProperty1
+import kotlin.reflect.full.memberProperties
+import kotlin.reflect.jvm.isAccessible
+
+
+enum class KeyframerFormat {
+    SIMPLE,
+    FULL
+}
+
+
+
+open class Keyframer {
+    private var currentTime = 0.0
+    operator fun invoke(time: Double) {
+        currentTime = time
+    }
+
+    open inner class CompoundChannel(val keys: Array<String>, private val defaultValues: Array<Double>) {
+        private var channelTimes: Array<Double> = Array(keys.size) { Double.NEGATIVE_INFINITY }
+        private var compoundChannels: Array<KeyframerChannel?> = Array(keys.size) { null }
+        private var cachedValues: Array<Double?> = Array(keys.size) { null }
+
+        open fun reset() {
+            for (i in channelTimes.indices) {
+                channelTimes[i] = Double.NEGATIVE_INFINITY
+            }
+        }
+
+        fun getValue(compound: Int): Double {
+            if (compoundChannels[compound] == null) {
+                compoundChannels[compound] = channels[keys[compound]]
+            }
+            return if (compoundChannels[compound] != null) {
+                if (channelTimes[compound] == currentTime && cachedValues[compound] != null) {
+                    cachedValues[compound] ?: defaultValues[compound]
+                } else {
+                    val value = compoundChannels[compound]?.value(currentTime) ?: defaultValues[compound]
+                    cachedValues[compound] = value
+                    value
+                }
+            } else {
+                defaultValues[compound]
+            }
+        }
+    }
+
+    val duration: Double
+        get() = channels.values.maxBy { it.duration() }?.duration() ?: 0.0
+
+
+    inner class DoubleChannel(key: String, defaultValue: Double = 0.0) :
+        CompoundChannel(arrayOf(key), arrayOf(defaultValue)) {
+        operator fun getValue(keyframer: Keyframer, property: KProperty<*>): Double = getValue(0)
+    }
+
+    inner class Vector2Channel(keys: Array<String>, defaultValue: Vector2 = Vector2.ZERO) :
+        CompoundChannel(keys, arrayOf(defaultValue.x, defaultValue.y)) {
+        operator fun getValue(keyframer: Keyframer, property: KProperty<*>): Vector2 = Vector2(getValue(0), getValue(1))
+    }
+
+    inner class Vector3Channel(keys: Array<String>, defaultValue: Vector3 = Vector3.ZERO) :
+        CompoundChannel(keys, arrayOf(defaultValue.x, defaultValue.y, defaultValue.z)) {
+        operator fun getValue(keyframer: Keyframer, property: KProperty<*>): Vector3 =
+            Vector3(getValue(0), getValue(1), getValue(2))
+    }
+
+    inner class Vector4Channel(keys: Array<String>, defaultValue: Vector4 = Vector4.ZERO) :
+        CompoundChannel(keys, arrayOf(defaultValue.x, defaultValue.y, defaultValue.z, defaultValue.w)) {
+        operator fun getValue(keyframer: Keyframer, property: KProperty<*>): Vector4 =
+            Vector4(getValue(0), getValue(1), getValue(2), getValue(3))
+    }
+
+    inner class RGBaChannel(keys: Array<String>, defaultValue: ColorRGBa = ColorRGBa.WHITE) :
+        CompoundChannel(keys, arrayOf(defaultValue.r, defaultValue.g, defaultValue.b, defaultValue.a)) {
+        operator fun getValue(keyframer: Keyframer, property: KProperty<*>): ColorRGBa =
+            ColorRGBa(getValue(0), getValue(1), getValue(2), getValue(3))
+    }
+
+    inner class RGBChannel(keys: Array<String>, defaultValue: ColorRGBa = ColorRGBa.WHITE) :
+        CompoundChannel(keys, arrayOf(defaultValue.r, defaultValue.g, defaultValue.b)) {
+        operator fun getValue(keyframer: Keyframer, property: KProperty<*>): ColorRGBa =
+            ColorRGBa(getValue(0), getValue(1), getValue(2))
+    }
+
+    val channels = mutableMapOf<String, KeyframerChannel>()
+
+    fun loadFromJson(
+        file: File,
+        format: KeyframerFormat = KeyframerFormat.SIMPLE,
+        parameters: Map<String, Double> = emptyMap(),
+        functions: FunctionExtensions = FunctionExtensions.EMPTY
+    ) {
+        require(file.exists()) {
+            "failed to load keyframer from json: '${file.absolutePath}' does not exist."
+        }
+        try {
+            loadFromJsonString(file.readText(), format, parameters, functions)
+        } catch (e: ExpressionException) {
+            throw ExpressionException("Error loading from '${file.path}': ${e.message ?: ""}")
+        }
+    }
+
+    fun loadFromJson(
+            url: URL,
+            format: KeyframerFormat = KeyframerFormat.SIMPLE,
+            parameters: Map<String, Double> = emptyMap(),
+            functions: FunctionExtensions = FunctionExtensions.EMPTY
+    ) {
+        try {
+            loadFromJsonString(url.readText(), format, parameters, functions)
+        } catch (e: ExpressionException) {
+            throw ExpressionException("Error loading $format from '${url}': ${e.message ?: ""}")
+        } catch(e: IllegalStateException) {
+            throw ExpressionException("Error loading $format from '${url}': ${e.message ?: ""}")
+        }
+    }
+
+    fun loadFromJsonString(
+        json: String,
+        format: KeyframerFormat = KeyframerFormat.SIMPLE,
+        parameters: Map<String, Double> = emptyMap(),
+        functions: FunctionExtensions = FunctionExtensions.EMPTY
+    ) {
+        when (format) {
+            KeyframerFormat.SIMPLE -> {
+                try {
+                    val type = object : TypeToken<List<Map<String, Any>>>() {}.type
+                    val keys: List<MutableMap<String, Any>> = Gson().fromJson(json, type)
+                    loadFromKeyObjects(keys, parameters, functions)
+                } catch (e: JsonSyntaxException) {
+                    error("Error parsing simple Keyframer data: ${e.cause?.message}")
+                }
+            }
+            KeyframerFormat.FULL -> {
+                try {
+                    val type = object : TypeToken<Map<String, Any>>() {}.type
+                    val keys: Map<String, Any> = Gson().fromJson(json, type)
+                    loadFromObjects(keys, parameters, functions)
+                } catch (e: JsonSyntaxException) {
+                    error("Error parsing full Keyframer data: ${e.cause?.message}")
+                }
+            }
+        }
+    }
+
+    private val parameters = mutableMapOf<String, Double>()
+    private val prototypes = mutableMapOf<String, Map<String, Any>>()
+
+    fun loadFromObjects(
+        dict: Map<String, Any>,
+        externalParameters: Map<String, Double> = emptyMap(),
+        functions: FunctionExtensions = FunctionExtensions.EMPTY
+    ) {
+        this.parameters.clear()
+        this.parameters.putAll(externalParameters)
+
+        prototypes.clear()
+        @Suppress("UNCHECKED_CAST")
+        (dict["parameters"] as? Map<String, Any>)?.let { lp ->
+            for (entry in lp) {
+                this.parameters[entry.key] = try {
+                    when (val candidate = entry.value) {
+                        is Double -> candidate
+                        is String -> evaluateExpression(candidate, parameters, functions)
+                            ?: error("could not evaluate expression: '$candidate'")
+                        is Int -> candidate.toDouble()
+                        is Float -> candidate.toDouble()
+                        else -> error("unknown type for parameter '${entry.key}'")
+                    }
+                } catch (e: ExpressionException) {
+                    throw ExpressionException("error in 'parameters': ${e.message ?: ""} ")
+                }
+            }
+        }
+        this.parameters.putAll(externalParameters)
+
+        @Suppress("UNCHECKED_CAST")
+        (dict["prototypes"] as? Map<String, Map<String, Any>>)?.let {
+            prototypes.putAll(it)
+        }
+
+        @Suppress("UNCHECKED_CAST")
+        (dict["keys"] as? List<Map<String, Any>>)?.let { keys ->
+            loadFromKeyObjects(keys, parameters, functions)
+        }
+    }
+
+    private fun resolvePrototype(prototypeNames: String): Map<String, Any> {
+        val prototypeTokens = prototypeNames.split(" ").map { it.trim() }.filter { it.isNotBlank() }
+        val prototypeRefs = prototypeTokens.mapNotNull { prototypes[it] }
+
+        val computed = mutableMapOf<String, Any>()
+        for (ref in prototypeRefs) {
+            computed.putAll(ref)
+        }
+        return computed
+    }
+
+    fun loadFromKeyObjects(
+        keys: List<Map<String, Any>>,
+        externalParameters: Map<String, Double>,
+        functions: FunctionExtensions
+    ) {
+        if (externalParameters !== parameters) {
+            parameters.clear()
+            parameters.putAll(externalParameters)
+        }
+
+        var lastTime = 0.0
+
+        val channelDelegates = this::class.memberProperties
+            .mapNotNull {
+                @Suppress("UNCHECKED_CAST")
+                it as? KProperty1<Keyframer, Any>
+            }
+            .filter { it.isAccessible = true; it.getDelegate(this) is CompoundChannel }
+            .associate { Pair(it.name, it.getDelegate(this) as CompoundChannel) }
+
+        val channelKeys = channelDelegates.values.flatMap { channel ->
+            channel.keys.map { it }
+        }.toSet()
+
+        for (delegate in channelDelegates.values) {
+            delegate.reset()
+        }
+
+        val expressionContext = mutableMapOf<String, Double>()
+        expressionContext.putAll(parameters)
+        expressionContext["t"] = 0.0
+
+
+        fun handleKey(key: Map<String, Any>, path: String) {
+
+            val prototype = (key["prototypes"] as? String)?.let {
+                resolvePrototype(it)
+            } ?: emptyMap()
+
+            val computed = mutableMapOf<String, Any>()
+            computed.putAll(prototype)
+            computed.putAll(key)
+
+            val time = try {
+                when (val candidate = computed["time"]) {
+                    null -> lastTime
+                    is String -> evaluateExpression(candidate, expressionContext, functions)
+                        ?: error { "unknown value format for time : $candidate" }
+                    is Double -> candidate
+                    is Int -> candidate.toDouble()
+                    is Float -> candidate.toDouble()
+                    else -> error("unknown time format for '$candidate'")
+                }
+            } catch (e: ExpressionException) {
+                throw ExpressionException("error in $path.'time': ${e.message ?: ""}")
+            }
+
+            val duration = try {
+                when (val candidate = computed["duration"]) {
+                    null -> 0.0
+                    is String -> evaluateExpression(candidate, expressionContext, functions)
+                        ?: error { "unknown value format for time : $candidate" }
+                    is Int -> candidate.toDouble()
+                    is Float -> candidate.toDouble()
+                    is Double -> candidate
+                    else -> error("unknown duration type for '$candidate")
+                }
+            } catch (e: ExpressionException) {
+                throw ExpressionException("error in $path.'duration': ${e.message ?: ""}")
+            }
+
+            val easing = try {
+                when (val easingCandidate = computed["easing"]) {
+                    null -> Easing.Linear.function
+                    is String -> when (easingCandidate) {
+                        "linear" -> Easing.Linear.function
+                        "cubic-in" -> Easing.CubicIn.function
+                        "cubic-out" -> Easing.CubicOut.function
+                        "cubic-in-out" -> Easing.CubicInOut.function
+                        "quad-in" -> Easing.QuadIn.function
+                        "quad-out" -> Easing.QuadOut.function
+                        "quad-in-out" -> Easing.QuadInOut.function
+                        "quart-in" -> Easing.QuartIn.function
+                        "quart-out" -> Easing.QuartOut.function
+                        "quart-in-out" -> Easing.QuartInOut.function
+                        "quint-in" -> Easing.QuintIn.function
+                        "quint-out" -> Easing.QuintOut.function
+                        "quint-in-out" -> Easing.QuintInOut.function
+                        "expo-in" -> Easing.ExpoIn.function
+                        "expo-out" -> Easing.ExpoOut.function
+                        "expo-in-out" -> Easing.ExpoInOut.function
+                        "one" -> Easing.One.function
+                        "zero" -> Easing.Zero.function
+                        else -> error("unknown easing name '$easingCandidate'")
+                    }
+                    else -> error("unknown easing for '$easingCandidate'")
+                }
+            } catch (e: IllegalStateException) {
+                throw ExpressionException("error in $path.'easing': ${e.message ?: ""}")
+            }
+
+            val hold = Hold.HoldNone
+
+            val reservedKeys = setOf("time", "easing", "hold")
+
+            for (channelCandidate in computed.filter { it.key !in reservedKeys }) {
+                if (channelCandidate.key in channelKeys) {
+                    val channel = channels.getOrPut(channelCandidate.key) {
+                        KeyframerChannel()
+                    }
+                    expressionContext["v"] = channel.lastValue() ?: 0.0
+                    val value = try {
+                        when (val candidate = channelCandidate.value) {
+                            is Double -> candidate
+                            is String -> evaluateExpression(candidate, expressionContext, functions)
+                                ?: error("unknown value format for key '${channelCandidate.key}' : $candidate")
+                            is Int -> candidate.toDouble()
+                            else -> error("unknown value type for key '${channelCandidate.key}' : $candidate")
+                        }
+                    } catch (e: ExpressionException) {
+                        throw ExpressionException("error in $path.'${channelCandidate.key}': ${e.message ?: ""}")
+                    }
+                    channel.add(time, value, easing, hold)
+                }
+            }
+            lastTime = time + duration
+            expressionContext["t"] = lastTime
+
+            if (computed.containsKey("repeat")) {
+                @Suppress("UNCHECKED_CAST")
+                val repeatObject = computed["repeat"] as? Map<String, Any> ?: error("'repeat' should be a map")
+                val count = try {
+                    when (val candidate = repeatObject["count"]) {
+                        null -> 1
+                        is Int -> candidate
+                        is Double -> candidate.toInt()
+                        is String -> evaluateExpression(candidate, expressionContext, functions)?.roundToInt()
+                            ?: error("cannot evaluate expression for count: '$candidate'")
+                        else -> error("unknown value type for count: '$candidate")
+                    }
+                } catch (e: ExpressionException) {
+                    throw ExpressionException("error in $path.repeat.'count': ${e.message ?: ""}")
+                }
+
+                @Suppress("UNCHECKED_CAST")
+                val repeatKeys = repeatObject["keys"] as? List<Map<String, Any>> ?: error("no repeat keys")
+
+                for (i in 0 until count) {
+                    expressionContext["rep"] = i.toDouble()
+                    for (repeatKey in repeatKeys) {
+                        handleKey(repeatKey, "$path.repeat")
+                    }
+                }
+            }
+        }
+
+        for ((index, key) in keys.withIndex()) {
+            handleKey(key, "keys[$index]")
+        }
+    }
+}
--- a/orx-keyframer/src/test/kotlin/TestExpressionErrors.kt
+++ b/orx-keyframer/src/test/kotlin/TestExpressionErrors.kt
@@ -0,0 +1,57 @@
+import org.amshove.kluent.`should throw`
+import org.amshove.kluent.`with message`
+import org.amshove.kluent.invoking
+import org.openrndr.extra.keyframer.ExpressionException
+import org.openrndr.extra.keyframer.evaluateExpression
+import org.spekframework.spek2.Spek
+import org.spekframework.spek2.style.specification.describe
+import java.lang.IllegalStateException
+
+object TestExpressionErrors : Spek({
+
+    describe("an expression with non-sensible writing") {
+        val expression = ")("
+        it("should cause an exception to be thrown when evaluated") {
+            invoking {
+                evaluateExpression(expression)
+            } `should throw`  ExpressionException::class `with message` "parser error in expression: ')('; [line: 1, character: 0 , near: [@0,0:0=')',<21>,1:0] ]"
+        }
+    }
+
+    describe("an expression with equality instead of assign") {
+        val expression = "a == 5"
+        it("should cause an exception to be thrown when evaluated") {
+            invoking {
+                evaluateExpression(expression)
+            }  `should throw` ExpressionException::class `with message` "parser error in expression: 'a == 5'; [line: 1, character: 3 , near: [@3,3:3='=',<19>,1:3] ]"
+        }
+    }
+
+    describe("an expression trying to reassign a number") {
+        val expression = "3 = 5"
+        it("should cause an exception to be thrown when evaluated") {
+            invoking {
+               evaluateExpression(expression)
+            } `should throw` ExpressionException::class `with message` "parser error in expression: '3 = 5'; [line: 1, character: 2 , near: [@2,2:2='=',<19>,1:2] ]"
+        }
+    }
+
+    describe("an expression that uses non-existing functions") {
+        val expression = "notExisting(5)"
+        it("should cause an exception to be thrown when evaluated") {
+            invoking {
+                evaluateExpression(expression)
+            } `should throw` ExpressionException::class `with message` "error in evaluation of 'notExisting(5)': unresolved function: 'notExisting(x0)'"
+        }
+    }
+
+    describe("an expression that uses non-existing variables") {
+        val expression = "notExisting + 4"
+        it("should cause an exception to be thrown when evaluated") {
+            invoking {
+                evaluateExpression(expression)
+            } `should throw` ExpressionException::class `with message` "error in evaluation of 'notExisting+4': unresolved variable: 'notExisting'"
+        }
+    }
+
+})
--- a/orx-keyframer/src/test/kotlin/TestFunctionCall.kt
+++ b/orx-keyframer/src/test/kotlin/TestFunctionCall.kt
@@ -0,0 +1,92 @@
+import org.amshove.kluent.shouldBeNear
+import org.openrndr.extra.keyframer.FunctionExtensions
+import org.openrndr.extra.keyframer.evaluateExpression
+import org.spekframework.spek2.Spek
+import org.spekframework.spek2.style.specification.describe
+
+object TestFunctionCall : Spek({
+    describe("a function call") {
+        val expression = "sqrt(4.0)"
+        val result = evaluateExpression(expression)
+        result?.shouldBeNear(2.0, 10E-6)
+    }
+
+    describe("two function calls") {
+        val expression = "sqrt(4.0) * sqrt(4.0)"
+        val result = evaluateExpression(expression)
+        result?.shouldBeNear(4.0, 10E-6)
+    }
+
+    describe("two argument function call") {
+        val expression = "max(0.0, 4.0)"
+        val result = evaluateExpression(expression)
+        result?.shouldBeNear(4.0, 10E-6)
+    }
+
+    describe("two argument function call") {
+        val expression = "min(8.0, 4.0)"
+        val result = evaluateExpression(expression)
+        result?.shouldBeNear(4.0, 10E-6)
+    }
+
+    describe("three argument function call") {
+        val expression = "mix(8.0, 4.0, 0.5)"
+        val result = evaluateExpression(expression)
+        result?.shouldBeNear(6.0, 10E-6)
+    }
+
+    describe("five argument function call") {
+        val expression = "map(0.0, 1.0, 0.0, 8.0, 0.5)"
+        val result = evaluateExpression(expression)
+        result?.shouldBeNear(4.0, 10E-6)
+    }
+
+    describe("two argument function call, where argument order matters") {
+        val expression = "pow(2.0, 3.0)"
+        val result = evaluateExpression(expression)
+        result?.shouldBeNear(8.0, 10E-6)
+    }
+
+    describe("nested function call") {
+        val expression = "sqrt(min(8.0, 4.0))"
+        val result = evaluateExpression(expression)
+        result?.shouldBeNear(2.0, 10E-6)
+    }
+
+    describe("extension function0 call") {
+        val expression = "extension()"
+        val result = evaluateExpression(expression, functions = FunctionExtensions(functions0 = mapOf("extension" to { 2.0 })))
+        result?.shouldBeNear(2.0, 10E-6)
+    }
+
+    describe("extension function1 call") {
+        val expression = "extension(1.0)"
+        val result = evaluateExpression(expression, functions = FunctionExtensions(functions1 = mapOf("extension" to { x -> x * 2.0 })))
+        result?.shouldBeNear(2.0, 10E-6)
+    }
+
+    describe("extension function2 call") {
+        val expression = "extension(1.0, 1.0)"
+        val result = evaluateExpression(expression, functions = FunctionExtensions(functions2 = mapOf("extension" to { x, y -> x + y })))
+        result?.shouldBeNear(2.0, 10E-6)
+    }
+
+    describe("extension function3 call") {
+        val expression = "extension(1.0, 1.0, 1.0)"
+        val result = evaluateExpression(expression, functions = FunctionExtensions(functions3 = mapOf("extension" to { x, y, z -> x + y + z})))
+        result?.shouldBeNear(3.0, 10E-6)
+    }
+
+    describe("extension function4 call") {
+        val expression = "extension(1.0, 1.0, 1.0, 1.0)"
+        val result = evaluateExpression(expression, functions = FunctionExtensions(functions4 = mapOf("extension" to { x, y, z, w  -> x + y + z + w})))
+        result?.shouldBeNear(4.0, 10E-6)
+    }
+
+    describe("extension function5 call") {
+        val expression = "extension(1.0, 1.0, 1.0, 1.0, 1.0)"
+        val result = evaluateExpression(expression, functions = FunctionExtensions(functions5 = mapOf("extension" to { x, y, z, w, u -> x + y + z + w + u})))
+        result?.shouldBeNear(5.0, 10E-6)
+    }
+
+})
--- a/orx-keyframer/src/test/kotlin/TestKeyframerChannel.kt
+++ b/orx-keyframer/src/test/kotlin/TestKeyframerChannel.kt
@@ -0,0 +1,35 @@
+import org.amshove.kluent.`should be`
+import org.amshove.kluent.shouldBeNear
+import org.openrndr.extra.keyframer.KeyframerChannel
+import org.openrndr.extras.easing.Easing
+import org.spekframework.spek2.Spek
+import org.spekframework.spek2.style.specification.describe
+
+object TestKeyframerChannel : Spek({
+
+    describe("a keyframer channel without keys") {
+        val kfc = KeyframerChannel()
+        it ("should return null when asking for value before first key time") {
+            kfc.value(0.0) `should be` null
+        }
+    }
+    describe("a keyframer channel with a single key") {
+        val kfc = KeyframerChannel()
+        kfc.add(0.0, 1.0, Easing.Linear.function)
+        kfc.value(0.0)?.shouldBeNear(1.0, 10E-6)
+
+        it ("should return null when asking for value before first key time") {
+            kfc.value(-1.0) `should be` null
+        }
+    }
+    describe("a keyframer channel with two keys") {
+        val kfc = KeyframerChannel()
+        kfc.add(0.0, 1.0, Easing.Linear.function)
+        kfc.add(1.0, 2.0, Easing.Linear.function)
+        kfc.value(0.0)?.shouldBeNear(1.0, 10E-6)
+
+        it ("should return null when asking for value before first key time") {
+            kfc.value(-1.0) `should be` null
+        }
+    }
+})
--- a/orx-keyframer/src/test/kotlin/TestKeyframerErrors.kt
+++ b/orx-keyframer/src/test/kotlin/TestKeyframerErrors.kt
@@ -0,0 +1,105 @@
+import org.amshove.kluent.`should throw`
+import org.amshove.kluent.`with message`
+import org.amshove.kluent.invoking
+import org.openrndr.extra.keyframer.ExpressionException
+import org.openrndr.extra.keyframer.Keyframer
+import org.openrndr.extra.keyframer.KeyframerFormat
+import org.spekframework.spek2.Spek
+import org.spekframework.spek2.style.specification.describe
+import java.io.File
+import kotlin.IllegalStateException
+
+
+private fun testFile(path: String) : File {
+    val test = File(".")
+    return if (test.absolutePath.endsWith("orx-keyframer/.")) {
+        File(path)
+    } else {
+        File("orx-keyframer/$path")
+    }
+}
+private fun testName(path: String) : String {
+    val test = File(".")
+    return if (test.absolutePath.endsWith("orx-keyframer/.")) {
+        path
+    } else {
+        "orx-keyframer/$path"
+    }
+}
+
+
+object TestKeyframerErrors : Spek({
+    class Animation : Keyframer() {
+        val position by Vector2Channel(arrayOf("x", "y"))
+    }
+
+    describe("loading a faulty json") {
+        val animation = Animation()
+        val json = """
+        """
+        it("should throw an exception") {
+            invoking { animation.loadFromJsonString(json) } `should throw` (IllegalStateException::class)
+        }
+    }
+
+    describe("loading a non existing json") {
+        val animation = Animation()
+        it("should throw an exception") {
+            invoking { animation.loadFromJson(testFile("this-does-not-exist")) } `should throw` (IllegalArgumentException::class)
+        }
+    }
+
+    describe("loading a json with a faulty time expression (1)") {
+
+        File(".").apply {
+            println(this.absolutePath)
+        }
+
+        val animation = Animation()
+        it("should throw an exception") {
+            invoking {
+                animation.loadFromJson(
+                        testFile("src/test/resources/error-reporting/time-01.json"),
+                        format = KeyframerFormat.SIMPLE
+                )
+            } `should throw` ExpressionException::class `with message` "Error loading from '${testName("src/test/resources/error-reporting/time-01.json")}': error in keys[0].'time': parser error in expression: ')('; [line: 1, character: 0 , near: [@0,0:0=')',<21>,1:0] ]"
+        }
+    }
+
+    describe("loading a json with a faulty time expression (2) ") {
+        val animation = Animation()
+        it("should throw an exception") {
+            invoking {
+                animation.loadFromJson(
+                        testFile("src/test/resources/error-reporting/time-02.json"),
+                        format = KeyframerFormat.SIMPLE
+                )
+            } `should throw` ExpressionException::class `with message` "Error loading from '${testName("src/test/resources/error-reporting/time-02.json")}': error in keys[0].'time': error in evaluation of 'doesNotExist': unresolved variable: 'doesNotExist'"
+        }
+    }
+
+    describe("loading a json with a non-existing easing") {
+        val animation = Animation()
+        it("should throw an exception") {
+            invoking {
+                animation.loadFromJson(
+                        testFile("src/test/resources/error-reporting/easing.json"),
+                        format = KeyframerFormat.SIMPLE
+                )
+            } `should throw` ExpressionException::class `with message` "Error loading from '${testName("src/test/resources/error-reporting/easing.json")}': error in keys[0].'easing': unknown easing name 'garble'"
+        }
+    }
+
+    describe("loading a json with a faulty value (1)") {
+        val animation = Animation()
+
+        it("should throw an exception") {
+            invoking {
+                animation.loadFromJson(
+                        testFile("src/test/resources/error-reporting/value-01.json"),
+                        format = KeyframerFormat.SIMPLE
+                )
+            } `should throw` ExpressionException::class `with message` "Error loading from '${testName("src/test/resources/error-reporting/value-01.json")}': error in keys[0].'x': error in evaluation of 'garble': unresolved variable: 'garble'"
+        }
+    }
+})
--- a/orx-keyframer/src/test/kotlin/TestOperators.kt
+++ b/orx-keyframer/src/test/kotlin/TestOperators.kt
@@ -0,0 +1,35 @@
+import org.amshove.kluent.shouldBeNear
+import org.openrndr.extra.keyframer.evaluateExpression
+import org.spekframework.spek2.Spek
+import org.spekframework.spek2.style.specification.describe
+
+object TestOperators : Spek({
+    describe("an addition operation") {
+        val result = evaluateExpression("1 + 2")
+        result?.shouldBeNear(3.0, 10E-6)
+    }
+    describe("a subtraction operation") {
+        val result = evaluateExpression("1 - 2")
+        result?.shouldBeNear(-1.0, 10E-6)
+    }
+    describe("a modulus operation") {
+        val result = evaluateExpression("4 % 2")
+        result?.shouldBeNear(0.0, 10E-6)
+    }
+    describe("a multiplication operation") {
+        val result = evaluateExpression("4 * 2")
+        result?.shouldBeNear(8.0, 10E-6)
+    }
+    describe("a division operation") {
+        val result = evaluateExpression("4 / 2")
+        result?.shouldBeNear(2.0, 10E-6)
+    }
+    describe("a multiplication/addition operation") {
+        val result = evaluateExpression("4 * 2 + 1")
+        result?.shouldBeNear(9.0, 10E-6)
+    }
+    describe("an addition/multiplication") {
+        val result = evaluateExpression("4 + 2 * 3")
+        result?.shouldBeNear(10.0, 10E-6)
+    }
+})
--- a/orx-keyframer/src/test/resources/error-reporting/easing.json
+++ b/orx-keyframer/src/test/resources/error-reporting/easing.json
@@ -0,0 +1,5 @@
+[
+  {
+    "easing": "garble"
+  }
+]
--- a/orx-keyframer/src/test/resources/error-reporting/time-01.json
+++ b/orx-keyframer/src/test/resources/error-reporting/time-01.json
@@ -0,0 +1,5 @@
+[
+  {
+    "time": ")("
+  }
+]
--- a/orx-keyframer/src/test/resources/error-reporting/time-02.json
+++ b/orx-keyframer/src/test/resources/error-reporting/time-02.json
@@ -0,0 +1,5 @@
+[
+  {
+    "time": "doesNotExist"
+  }
+]
--- a/orx-keyframer/src/test/resources/error-reporting/value-01.json
+++ b/orx-keyframer/src/test/resources/error-reporting/value-01.json
@@ -0,0 +1,7 @@
+[
+  {
+    "time": "0.0",
+    "x": "garble",
+    "y": "garble"
+  }
+]