1 files changed, 120 insertions, 0 deletions
diff --git a/demos/opengl/icosphere.cpp b/demos/opengl/icosphere.cpp
new file mode 100644
index 000000000..39444cbb6
--- /dev/null
+++ b/demos/opengl/icosphere.cpp
@@ -0,0 +1,120 @@
+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra.
+//
+// Copyright (C) 2008 Gael Guennebaud <gael.guennebaud@inria.fr>
+//
+// This Source Code Form is subject to the terms of the Mozilla
+// Public License v. 2.0. If a copy of the MPL was not distributed
+// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#include "icosphere.h"
+
+#include <GL/gl.h>
+#include <map>
+
+using namespace Eigen;
+
+//--------------------------------------------------------------------------------
+// icosahedron data
+//--------------------------------------------------------------------------------
+#define X .525731112119133606
+#define Z .850650808352039932
+
+static GLfloat vdata[12][3] = {
+   {-X, 0.0, Z}, {X, 0.0, Z}, {-X, 0.0, -Z}, {X, 0.0, -Z},
+   {0.0, Z, X}, {0.0, Z, -X}, {0.0, -Z, X}, {0.0, -Z, -X},
+   {Z, X, 0.0}, {-Z, X, 0.0}, {Z, -X, 0.0}, {-Z, -X, 0.0}
+};
+
+static GLint tindices[20][3] = {
+   {0,4,1}, {0,9,4}, {9,5,4}, {4,5,8}, {4,8,1},
+   {8,10,1}, {8,3,10}, {5,3,8}, {5,2,3}, {2,7,3},
+   {7,10,3}, {7,6,10}, {7,11,6}, {11,0,6}, {0,1,6},
+   {6,1,10}, {9,0,11}, {9,11,2}, {9,2,5}, {7,2,11} };
+//--------------------------------------------------------------------------------
+
+IcoSphere::IcoSphere(unsigned int levels)
+{
+  // init with an icosahedron
+  for (int i = 0; i < 12; i++)
+    mVertices.push_back(Map<Vector3f>(vdata[i]));
+  mIndices.push_back(new std::vector<int>);
+  std::vector<int>& indices = *mIndices.back();
+  for (int i = 0; i < 20; i++)
+  {
+    for (int k = 0; k < 3; k++)
+      indices.push_back(tindices[i][k]);
+  }
+  mListIds.push_back(0);
+
+  while(mIndices.size()<levels)
+    _subdivide();
+}
+
+const std::vector<int>& IcoSphere::indices(int level) const
+{
+  while (level>=int(mIndices.size()))
+    const_cast<IcoSphere*>(this)->_subdivide();
+  return *mIndices[level];
+}
+
+void IcoSphere::_subdivide(void)
+{
+  typedef unsigned long long Key;
+  std::map<Key,int> edgeMap;
+  const std::vector<int>& indices = *mIndices.back();
+  mIndices.push_back(new std::vector<int>);
+  std::vector<int>& refinedIndices = *mIndices.back();
+  int end = indices.size();
+  for (int i=0; i<end; i+=3)
+  {
+    int ids0[3],  // indices of outer vertices
+        ids1[3];  // indices of edge vertices
+    for (int k=0; k<3; ++k)
+    {
+      int k1 = (k+1)%3;
+      int e0 = indices[i+k];
+      int e1 = indices[i+k1];
+      ids0[k] = e0;
+      if (e1>e0)
+        std::swap(e0,e1);
+      Key edgeKey = Key(e0) | (Key(e1)<<32);
+      std::map<Key,int>::iterator it = edgeMap.find(edgeKey);
+      if (it==edgeMap.end())
+      {
+        ids1[k] = mVertices.size();
+        edgeMap[edgeKey] = ids1[k];
+        mVertices.push_back( (mVertices[e0]+mVertices[e1]).normalized() );
+      }
+      else
+        ids1[k] = it->second;
+    }
+    refinedIndices.push_back(ids0[0]); refinedIndices.push_back(ids1[0]); refinedIndices.push_back(ids1[2]);
+    refinedIndices.push_back(ids0[1]); refinedIndices.push_back(ids1[1]); refinedIndices.push_back(ids1[0]);
+    refinedIndices.push_back(ids0[2]); refinedIndices.push_back(ids1[2]); refinedIndices.push_back(ids1[1]);
+    refinedIndices.push_back(ids1[0]); refinedIndices.push_back(ids1[1]); refinedIndices.push_back(ids1[2]);
+  }
+  mListIds.push_back(0);
+}
+
+void IcoSphere::draw(int level)
+{
+  while (level>=int(mIndices.size()))
+    const_cast<IcoSphere*>(this)->_subdivide();
+  if (mListIds[level]==0)
+  {
+    mListIds[level] = glGenLists(1);
+    glNewList(mListIds[level], GL_COMPILE);
+      glVertexPointer(3, GL_FLOAT, 0, mVertices[0].data());
+      glNormalPointer(GL_FLOAT, 0, mVertices[0].data());
+      glEnableClientState(GL_VERTEX_ARRAY);
+      glEnableClientState(GL_NORMAL_ARRAY);
+      glDrawElements(GL_TRIANGLES, mIndices[level]->size(), GL_UNSIGNED_INT, &(mIndices[level]->at(0)));
+      glDisableClientState(GL_VERTEX_ARRAY);
+      glDisableClientState(GL_NORMAL_ARRAY);
+    glEndList();
+  }
+  glCallList(mListIds[level]);
+}
+
+