[orx-mesh, orx-mesh-noise] Add orx-mesh-noise

orx-mesh-noise/src/commonMain/kotlin/MeshNoise.kt

@@ -0,0 +1,65 @@
+package org.openrndr.extra.mesh.noise
+
+import org.openrndr.extra.mesh.IIndexedPolygon
+import org.openrndr.extra.mesh.IMeshData
+import org.openrndr.extra.mesh.IVertexData
+import org.openrndr.math.Vector3
+import kotlin.math.sqrt
+import kotlin.random.Random
+
+/**
+ * Generate a uniformly distributed barycentric coordinate
+ * @param random a random number generator
+ */
+fun uniformBarycentric(random: Random = Random.Default): Vector3 {
+    val u = random.nextDouble()
+    val v = random.nextDouble()
+    val su0 = sqrt(u)
+    val b0 = 1.0 - su0
+    val b1 = v * su0
+    return Vector3(b0, b1, 1.0 - b0 - b1)
+}
+
+/**
+ * Generate a uniformly distributed point that lies inside this [IIndexedPolygon]
+ * @param vertexData vertex data used to resolve positions
+ * @param random a random number generator
+ */
+fun IIndexedPolygon.uniform(vertexData: IVertexData, random: Random = Random.Default): Vector3 {
+    require(positions.size == 3) { "polygon must be a triangle"}
+
+    val x = vertexData.positions.slice(positions)
+    val b = uniformBarycentric(random)
+    return x[0] * b.x + x[1] * b.y + x[2] * b.z
+}
+
+internal fun IIndexedPolygon.area(vertexData: IVertexData): Double {
+    require(positions.size == 3) { "polygon must be a triangle"}
+    val x = vertexData.positions.slice(positions)
+    val u = x[1] - x[0]
+    val v = x[2] - x[0]
+    return u.areaBetween(v) / 2.0
+}
+
+/**
+ * Generate points on the surface described by the mesh data
+ */
+fun IMeshData.uniform(count: Int, random: Random = Random.Default): List<Vector3> {
+    val triangulated = triangulate()
+    val result = mutableListOf<Vector3>()
+    val totalArea = triangulated.polygons.sumOf { it.area(vertexData) }
+    val randoms = (0 until count).map {
+        random.nextDouble(totalArea)
+    }.sorted()
+
+    var idx = 0
+    var sum = 0.0
+    for (t in triangulated.polygons) {
+        sum += t.area(vertexData)
+        while (idx <= randoms.lastIndex && sum > randoms[idx]) {
+            result.add(t.uniform(vertexData, random))
+            idx++
+        }
+    }
+    return result
+}