sphere.cpp

//! \p detail can be between 0 ( = icosahedron) and 8 (extremely detailed sphere)
//! a value of 2 yelds already very good results.
ref<Geometry> vl::makeIcosphere(const vec3& pos, Real diameter, int detail, bool remove_doubles)
{
  ref<Geometry> geom = new Geometry;
  geom->setObjectName("Icosphere");

  ref<ArrayFloat3> coords = new ArrayFloat3;
  ref<ArrayFloat3> norms = new ArrayFloat3;

  ref<DrawElementsUInt> polys = new DrawElementsUInt(PT_TRIANGLES);

  const Real X = (Real)0.525731112119133606;
  const Real Z = (Real)0.850650808352039932;
  std::vector< vec3 > verts;
  verts.push_back( vec3(-X, 0, Z) );
  verts.push_back( vec3(X, 0, Z) );
  verts.push_back( vec3(-X, 0, -Z) );
  verts.push_back( vec3(X, 0, -Z) );
  verts.push_back( vec3(0, Z, X) );
  verts.push_back( vec3(0, Z, -X) );
  verts.push_back( vec3(0, -Z, X) );
  verts.push_back( vec3(0, -Z, -X) );
  verts.push_back( vec3(Z, X, 0) );
  verts.push_back( vec3(-Z, X, 0) );
  verts.push_back( vec3(Z, -X, 0) );
  verts.push_back( vec3(-Z, -X, 0) );

  int idxs[] = { 
    1,4,0, 4,9,0, 4,5,9, 8,5,4, 1,8,4, 
    1,10,8, 10,3,8, 8,3,5, 3,2,5, 3,7,2, 
    3,10,7, 10,6,7, 6,11,7, 6,0,11, 6,1,0,
    10,1,6, 11,0,9, 2,11,9, 5,2,9, 11,2,7
  };

  std::vector<int> indices;
  for(int i=0; i<4*5*3; ++i)
    indices.push_back(idxs[i]);

  // triangulate the icosahedron
  if (detail>8)
    detail = 8;
  if (detail<0)
    detail = 0;
  for(int i=0; i<detail; ++i)
  {
    std::vector<int> indices2;
    std::vector< vec3 > verts2;
    for( int j=0, idx=0; j<(int)indices.size(); j+=3)
    {
      indices2.push_back(idx++); indices2.push_back(idx++); indices2.push_back(idx++);
      indices2.push_back(idx++); indices2.push_back(idx++); indices2.push_back(idx++);
      indices2.push_back(idx++); indices2.push_back(idx++); indices2.push_back(idx++);
      indices2.push_back(idx++); indices2.push_back(idx++); indices2.push_back(idx++);

      vec3 v1 = verts[ indices[j+0] ]; v1.normalize();
      vec3 v2 = verts[ indices[j+1] ]; v2.normalize();
      vec3 v3 = verts[ indices[j+2] ]; v3.normalize();
      vec3 a = (v1 + v2) * 0.5f; a.normalize();
      vec3 b = (v2 + v3) * 0.5f; b.normalize();
      vec3 c = (v3 + v1) * 0.5f; c.normalize();
      verts2.push_back(v1); verts2.push_back( a); verts2.push_back(c);
      verts2.push_back( a); verts2.push_back(v2); verts2.push_back(b);
      verts2.push_back( a); verts2.push_back( b); verts2.push_back(c);
      verts2.push_back( c); verts2.push_back( b); verts2.push_back(v3);
    }
    verts = verts2;
    indices = indices2;
  }

  // generate sphere vertices and connection information

  Real radius = diameter / 2;

  coords->resize( (int)verts.size() );
  norms->resize( (int)verts.size() );
  for( int i=0; i<(int)verts.size(); ++i )
  {
    coords->at(i) = (fvec3)(verts[i]*radius + pos);
    vec3 n = verts[i];
    n.normalize();
    norms->at(i) = (fvec3)n;
  }

  polys->indices()->resize( (int)indices.size() );
  for(int i=0; i<(int)indices.size(); ++i)
  {
    VL_CHECK( indices[i] < (int)coords->size() )
    polys->indices()->at(i) = indices[i];
  }

  geom->setVertexArray(coords.get());
  geom->setNormalArray(norms.get());
  geom->drawCalls()->push_back(polys.get());

  if (remove_doubles)
  {
    DoubleVertexRemover dvr;
    dvr.removeDoubles(geom.get());
  }

#if defined(VL_OPENGL_ES1) || defined(VL_OPENGL_ES2)
  geom->makeGLESFriendly();
#endif

  return geom;
}