Improve mesh generator (#301)

Co-authored-by: Edwin Jakobs <edwin@rndr.studio>

orx-mesh-generators/src/commonMain/kotlin/Frames.kt

@@ -0,0 +1,60 @@
+package org.openrndr.extra.meshgenerators
+
+import org.openrndr.math.Matrix44
+import org.openrndr.math.Vector3
+import org.openrndr.math.Vector4
+import org.openrndr.math.transforms.buildTransform
+
+/**
+ * Calculate frames (pose matrices) using parallel transport
+ * @param up0 initial up vector, should not be collinear with `this[1] - this[0]`
+ */
+fun List<Vector3>.frames(up0: Vector3): List<Matrix44> {
+    val result = mutableListOf<Matrix44>()
+
+    if (this.isEmpty()) {
+        return emptyList()
+    }
+
+    if (this.size == 1) {
+        return listOf(Matrix44.IDENTITY)
+    }
+
+    var up = up0.normalized
+    run {
+        val current = this[0]
+        val next = this[1]
+        val forward = (next - current).normalized
+        val right = (forward cross up).normalized
+        up = ((right cross forward)).normalized
+        result.add(Matrix44.fromColumnVectors(right.xyz0, up.xyz0, forward.xyz0, current.xyz1))
+    }
+
+    require(up.length > 0.0) { "initial `up.length` is zero in .frames()" }
+
+    for (i in 1 until size - 1) {
+        val prev = this[i - 1]
+        val current = this[i]
+        val next = this[i + 1]
+        val f1 = (next - current).normalized
+        val f0 = (current - prev).normalized
+
+        val forward = (f0 + f1).normalized
+        require(forward.length > 0.0) { "`forward.length` is zero in .frames()" }
+        val right = (forward cross up).normalized
+        up = ((right cross forward)).normalized
+
+        require(up.length > 0.0) { "`up.length` is zero in .frames()" }
+        require(right.length > 0.0) { "`right.length` is zero in .frames()" }
+
+        //val m = Matrix44.fromColumnVectors(right.xyz0, up.xyz0, forward.xyz0, current.xyz1)
+
+        val m = buildTransform {
+            translate(current)
+            multiply(Matrix44.fromColumnVectors(right.xyz0, up.xyz0, forward.xyz0, Vector4.UNIT_W))
+        }
+
+        result.add(m)
+    }
+    return result
+}