From a9fa814a1a77c78961bfc332312720e3c25066eb Mon Sep 17 00:00:00 2001
From: Abe Pazos <abe@hamoid.com>
Date: Sun, 15 Mar 2020 15:55:38 +0100
Subject: [PATCH] Add Dodecahedron.kt

---
 .../src/main/kotlin/Dodecahedron.kt           | 82 +++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 orx-mesh-generators/src/main/kotlin/Dodecahedron.kt

diff --git a/orx-mesh-generators/src/main/kotlin/Dodecahedron.kt b/orx-mesh-generators/src/main/kotlin/Dodecahedron.kt
new file mode 100644
index 00000000..c86f3768
--- /dev/null
+++ b/orx-mesh-generators/src/main/kotlin/Dodecahedron.kt
@@ -0,0 +1,82 @@
+package org.openrndr.extras.meshgenerators
+
+import org.openrndr.draw.VertexBuffer
+import org.openrndr.math.Vector2
+import org.openrndr.math.Vector3
+import kotlin.math.sqrt
+
+// Based on
+// https://github.com/mrdoob/three.js/blob/master/src/geometries/DodecahedronGeometry.js
+
+// Create:
+//   val dode = dodecahedronMesh(400.0)
+// Draw:
+//   drawer.vertexBuffer(dode, DrawPrimitive.TRIANGLES)
+
+fun dodecahedronMesh(radius: Double = 1.0): VertexBuffer {
+    val vb = meshVertexBuffer(12 * 3 * 3)
+    vb.put {
+        generateDodecahedron(radius, bufferWriter(this))
+    }
+    return vb
+}
+
+fun generateDodecahedron(radius: Double = 1.0, writer: VertexWriter) {
+
+    val t = (1.0 + sqrt(5.0)) / 2;
+    val r = 1 / t;
+
+    val vertices = listOf(
+            // (±1, ±1, ±1)
+            -1.0, -1.0, -1.0, -1.0, -1.0, 1.0,
+            -1.0, 1.0, -1.0, -1.0, 1.0, 1.0,
+            1.0, -1.0, -1.0, 1.0, -1.0, 1.0,
+            1.0, 1.0, -1.0, 1.0, 1.0, 1.0,
+
+            // (0, ±1/φ, ±φ)
+            0.0, -r, -t, 0.0, -r, t,
+            0.0, r, -t, 0.0, r, t,
+
+            // (±1/φ, ±φ, 0)
+            -r, -t, 0.0, -r, t, 0.0,
+            r, -t, 0.0, r, t, 0.0,
+
+            // (±φ, 0, ±1/φ)
+            -t, 0.0, -r, t, 0.0, -r,
+            -t, 0.0, r, t, 0.0, r
+    );
+
+    val indices = listOf(
+            3, 11, 7, 3, 7, 15, 3, 15, 13,
+            7, 19, 17, 7, 17, 6, 7, 6, 15,
+            17, 4, 8, 17, 8, 10, 17, 10, 6,
+            8, 0, 16, 8, 16, 2, 8, 2, 10,
+            0, 12, 1, 0, 1, 18, 0, 18, 16,
+            6, 10, 2, 6, 2, 13, 6, 13, 15,
+            2, 16, 18, 2, 18, 3, 2, 3, 13,
+            18, 1, 9, 18, 9, 11, 18, 11, 3,
+            4, 14, 12, 4, 12, 0, 4, 0, 8,
+            11, 9, 5, 11, 5, 19, 11, 19, 7,
+            19, 5, 14, 19, 14, 4, 19, 4, 17,
+            1, 12, 14, 1, 14, 5, 1, 5, 9
+    );
+
+    // TODO: assign texture uv coordinates
+    // cylindrical? spherical?
+    // billboarding pentagons?
+    // unwrap?
+    val uv = Vector2(0.0)
+    val ii = indices.iterator()
+    while (ii.hasNext()) {
+        val tri = List(3) {
+            val i = ii.next()
+            Vector3(vertices[i * 3],
+                    vertices[i * 3 + 1],
+                    vertices[i * 3 + 2]) * radius
+        }
+        val up = (tri[1] - tri[0]).cross(tri[2] - tri[0]).normalized;
+        writer(tri[0], up, uv)
+        writer(tri[1], up, uv)
+        writer(tri[2], up, uv)
+    }
+}
\ No newline at end of file