demos/opengl/icosphere.cpp

// 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]);
}