Add DemoNoClear.kt

orx-no-clear/build.gradle

@@ -0,0 +1,19 @@
+sourceSets {
+    demo {
+        java {
+            srcDirs = ["src/demo/kotlin"]
+            compileClasspath += main.getCompileClasspath()
+            runtimeClasspath += main.getRuntimeClasspath()
+        }
+    }
+}
+
+dependencies {
+    //implementation project(":orx-?")
+
+    demoImplementation("org.openrndr:openrndr-core:$openrndrVersion")
+    demoImplementation("org.openrndr:openrndr-extensions:$openrndrVersion")
+    demoRuntimeOnly("org.openrndr:openrndr-gl3:$openrndrVersion")
+    demoRuntimeOnly("org.openrndr:openrndr-gl3-natives-$openrndrOS:$openrndrVersion")
+    demoImplementation(sourceSets.getByName("main").output)
+}

orx-no-clear/src/demo/kotlin/DemoNoClear.kt

@@ -0,0 +1,72 @@
+import org.openrndr.application
+import org.openrndr.color.ColorHSLa
+import org.openrndr.color.rgb
+import org.openrndr.draw.isolated
+import org.openrndr.extensions.SingleScreenshot
+import org.openrndr.extra.noclear.NoClear
+import org.openrndr.math.Polar
+import org.openrndr.shape.contour
+import kotlin.math.sin
+
+fun main() {
+    application {
+        program {
+            var time = 0.0
+
+            // -- this block is for automation purposes only
+            if (System.getProperty("takeScreenshot") == "true") {
+                extend(SingleScreenshot()) {
+                    this.delayFrames = 120
+                    this.outputFile = System.getProperty("screenshotPath")
+                }
+            }
+
+            // ------------------------------------------------------------
+            // By default OPENRNDR clears the canvas on each animation
+            // frame. NoClear disables that behavior, letting you
+            // draw on top of what you drew previously.
+            // That's the default in some other frameworks.
+            // ------------------------------------------------------------
+            extend(NoClear()) {
+                // backdrop is optional and it sets the initial state
+                // of the canvas. It can be a generative pattern, an image
+                // loaded from disk... In this case we start with dark gray.
+                backdrop = { drawer.clear(rgb(0.15)) }
+            }
+
+            extend {
+                // Draw something. For this demo *what* you draw is not so
+                // important, only the fact that it stays on the canvas
+                // until you draw something else on top of it.
+
+                drawer.isolated {
+                    // center the origin
+                    translate(bounds.center)
+
+                    for(i in 0..5) {
+                        time += 0.01
+
+                        // Make a list of 4 points rotating around the center at
+                        // different speeds
+                        val points = List(4) {
+                            Polar(time * (15.0 + it * 5),
+                                    250.0 * sin(time + it * 65)).cartesian
+                        }
+
+                        // Use those 4 points to create a bezier curve
+                        val c = contour {
+                            moveTo(points.first())
+                            curveTo(points[1], points[2], points.last())
+                        }
+
+                        // Draw the curve with increasing hue and lightness modulation
+                        fill = null
+                        stroke = ColorHSLa(time * 10.0, 0.8,
+                                0.5 + 0.2 * sin(time * 3), 0.5).toRGBa()
+                        contour(c)
+                    }
+                }
+            }
+        }
+    }
+}