Add new extrusion types, refactor code. (#323)

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

@@ -0,0 +1,112 @@
+package org.openrndr.extra.meshgenerators
+
+import org.openrndr.math.Matrix44
+import org.openrndr.math.Vector2
+import org.openrndr.math.Vector3
+import org.openrndr.math.Vector4
+import org.openrndr.math.transforms.normalMatrix
+import org.openrndr.shape.Path3D
+import org.openrndr.shape.Shape
+import org.openrndr.shape.Triangle
+
+/**
+ * Writes two triangles to [writer] representing
+ * the quad formed by four vertices.
+ *
+ * @param v00 vertex (0, 0)
+ * @param v01 vertex (0, 1)
+ * @param v10 vertex (1, 0)
+ * @param v11 vertex (1, 1)
+ * @param faceNormal the face normal
+ * @param writer the vertex writer function
+ */
+fun quadToTris(
+    v00: Vector3,
+    v01: Vector3,
+    v10: Vector3,
+    v11: Vector3,
+    faceNormal: Vector3,
+    writer: VertexWriter
+) {
+    writeTri(v11, v01, v00, Vector2.ZERO, Vector2.ZERO, Vector2.ZERO, faceNormal, writer)
+    writeTri(v00, v10, v11, Vector2.ZERO, Vector2.ZERO, Vector2.ZERO, faceNormal, writer)
+}
+
+/**
+ * Writes a triangle to [writer].
+ *
+ * @param v0 vertex 0
+ * @param v1 vertex 1
+ * @param v2 vertex 2
+ * @param tc0 texture coordinate 0
+ * @param tc1 texture coordinate 1
+ * @param tc2 texture coordinate 2
+ * @param faceNormal the face normal
+ * @param writer the vertex writer function
+ */
+fun writeTri(
+    v0: Vector3, v1: Vector3, v2: Vector3,
+    tc0: Vector2, tc1: Vector2, tc2: Vector2,
+    faceNormal: Vector3,
+    writer: VertexWriter
+) {
+    writer(v0, faceNormal, tc0)
+    writer(v1, faceNormal, tc1)
+    writer(v2, faceNormal, tc2)
+}
+
+/**
+ * Writes a list of triangles transformed by the [frame]
+ * transformation matrix into [writer].
+ *
+ * @param triangulation the list of triangles to write
+ * @param frame a transformation matrix to apply to each triangle
+ * @param flipNormals generates inside-out geometry if true
+ * @param writer the vertex writer function
+ */
+fun triangulationWithFrame(
+    triangulation: List<Triangle>,
+    frame: Matrix44,
+    flipNormals: Boolean = true,
+    writer: VertexWriter
+) {
+    val normalFrame = normalMatrix(frame)
+    val normalScale = if (!flipNormals) -1.0 else 1.0
+    val normal = ((normalFrame * Vector4(0.0, 0.0, normalScale, 0.0)).xyz)
+    for (triangle in triangulation) {
+        val t = if (!flipNormals) triangle else Triangle(triangle.x3, triangle.x2, triangle.x1)
+        writer((frame * t.x1.xy01).xyz, normal, Vector2.ZERO)
+        writer((frame * t.x2.xy01).xyz, normal, Vector2.ZERO)
+        writer((frame * t.x3.xy01).xyz, normal, Vector2.ZERO)
+    }
+}
+
+/**
+ * Adds caps to an extruded shape
+ *
+ * @param linearShape the cross-section of the mesh
+ * @param path the 3D path
+ * @param startCap adds a start cap if set to true
+ * @param endCap adds an end cap if set to true
+ * @param frames a list of matrices holding the transformation matrices along
+ * the path
+ * @param writer the vertex writer function
+ */
+fun extrudeCaps(
+    linearShape: Shape,
+    path: Path3D,
+    startCap: Boolean,
+    endCap: Boolean,
+    frames: List<Matrix44>,
+    writer: VertexWriter
+) {
+    if ((startCap || endCap) && !path.closed) {
+        val capTriangles = linearShape.triangulation
+        if (startCap) {
+            triangulationWithFrame(capTriangles, frames.first(), false, writer)
+        }
+        if (endCap) {
+            triangulationWithFrame(capTriangles, frames.last(), true, writer)
+        }
+    }
+}