From 113de04cbe5f76def0eb2e36ea2c0ec938a90e3b Mon Sep 17 00:00:00 2001
From: Tyler Hallada <tyler@hallada.net>
Date: Mon, 4 Feb 2019 01:43:11 -0500
Subject: [PATCH] Finally a hex sphere, albeit pointy

I still need to flatten the hexagons and pentagons to make it a true dual
polyhedron of the icosahedron.

Also needs performance improvements. Like caching the vertices, switching from
fan subdivision to a different method that represents hexagons and pentagons
with less triangles.
---
 package.json |  2 +-
 src/index.js | 96 +++++++++++++++++++++++++++++++++++++++++++++-------
 2 files changed, 85 insertions(+), 13 deletions(-)

diff --git a/package.json b/package.json
index 5ed6708..3cd6063 100644
--- a/package.json
+++ b/package.json
@@ -5,7 +5,7 @@
   "main": "index.js",
   "scripts": {
     "test": "echo \"Error: no test specified\" && exit 1",
-    "start": "webpack-dev-server --mode development --watch-poll --progress --hot",
+    "start": "webpack-dev-server --mode development --watch --progress --hot",
     "build": "webpack"
   },
   "author": "",
diff --git a/src/index.js b/src/index.js
index 89b61fb..1dd13a7 100644
--- a/src/index.js
+++ b/src/index.js
@@ -5,24 +5,96 @@ var OrbitControls = require("three-orbit-controls")(THREE);
 const scene = new THREE.Scene();
 var camera = new THREE.PerspectiveCamera(50, window.innerWidth / window.innerHeight, 0.1, 1000);
 
-var geometry = new THREE.IcosahedronBufferGeometry(5, 7);
+var geometry = new THREE.IcosahedronGeometry(10, 2);
 
-var position = geometry.getAttribute("position");
-var colors = [];
-var color = new THREE.Color(Math.random(), Math.random(), Math.random());
-for (var i = 0; i < position.count / 3; i += 1) {
-  color.setRGB(i / (position.count / 3), i / (position.count / 3), i / (position.count / 3));
-  colors.push(color.r, color.g, color.b);
-  colors.push(color.r, color.g, color.b);
-  colors.push(color.r, color.g, color.b);
+var vertToFaces = {};
+var newVertices = geometry.vertices;
+var newFaces = [];
+
+for (var i = 0; i < geometry.faces.length; i += 1) {
+  var face = geometry.faces[i];
+
+  if (vertToFaces[face.a]) {
+    vertToFaces[face.a].push(i);
+  } else {
+    vertToFaces[face.a] = [i];
+  }
+
+  if (vertToFaces[face.b]) {
+    vertToFaces[face.b].push(i);
+  } else {
+    vertToFaces[face.b] = [i];
+  }
+
+  if (vertToFaces[face.c]) {
+    vertToFaces[face.c].push(i);
+  } else {
+    vertToFaces[face.c] = [i];
+  }
+}
+
+var originalVertCount = geometry.vertices.length;
+
+var faceCentroids = {};
+for (var i = 0; i < geometry.faces.length; i += 1) {
+  var face = geometry.faces[i];
+  var vertexA = geometry.vertices[face.a];
+  var vertexB = geometry.vertices[face.b];
+  var vertexC = geometry.vertices[face.c];
+  var centroid = new THREE.Vector3(
+    (vertexA.x + vertexB.x + vertexC.x) / 3,
+    (vertexA.y + vertexB.y + vertexC.y) / 3,
+    (vertexA.z + vertexB.z + vertexC.z) / 3,
+  );
+
+  var centroidIndex = newVertices.push(centroid) - 1;
+  faceCentroids[i] = centroidIndex;
+}
+
+for (var i = 0; i < originalVertCount; i += 1) {
+  var faces = vertToFaces[i];
+  var color = new THREE.Color(Math.random(), Math.random(), Math.random());
+  for (var j = 0; j < faces.length; j += 1) {
+    var faceIndex = faces[j];
+    var face = geometry.faces[faceIndex];
+    var nonCenterVerts = [face.a, face.b, face.c].filter(vert => vert !== i);
+    var sortedFace = new THREE.Face3(i, nonCenterVerts[0], nonCenterVerts[1]);
+
+    var vertexA = geometry.vertices[sortedFace.a];
+    var vertexB = geometry.vertices[sortedFace.b];
+    var vertexC = geometry.vertices[sortedFace.c];
+    var halfAB = vertexA.clone().lerp(vertexB, 0.5);
+    var halfAC = vertexA.clone().lerp(vertexC, 0.5);
+    var halfBC = vertexB.clone().lerp(vertexC, 0.5);
+
+    // TODO: cache these and retrieve in future iteration (use .toFixed(3) in hash)
+    var centroidIndex = faceCentroids[faceIndex];
+    var halfABIndex = newVertices.push(halfAB) - 1;
+    var halfACIndex = newVertices.push(halfAC) - 1;
+    var halfBCIndex = newVertices.push(halfBC) - 1;
+
+    var face1 = new THREE.Face3(sortedFace.a, centroidIndex, halfABIndex);
+    face1.color = color;
+    var face2 = new THREE.Face3(sortedFace.a, centroidIndex, halfACIndex);
+    face2.color = color;
+
+    newFaces.push(face1, face2);
+  }
 }
 
 function disposeArray() {
   this.array = null;
 }
-geometry.addAttribute("color", new THREE.Float32BufferAttribute(colors, 3).onUpload(disposeArray));
-var material = new THREE.MeshBasicMaterial({ vertexColors: THREE.FaceColors });
-var sphere = new THREE.Mesh(geometry, material);
+
+var newGeometry = new THREE.Geometry();
+newGeometry.vertices = newVertices;
+newGeometry.faces = newFaces;
+newGeometry.computeFaceNormals();
+newGeometry.computeVertexNormals();
+newGeometry.normalize();
+
+var material = new THREE.MeshBasicMaterial({ vertexColors: THREE.FaceColors, side: THREE.DoubleSide });
+var sphere = new THREE.Mesh(newGeometry, material);
 scene.add(sphere);
 
 var controls = new OrbitControls(camera);