//***************************************************************************************
// Name: Subdivide
// Desc: Function subdivides every input triangle into four triangles of equal area.
//***************************************************************************************
void Subdivide(VertexList& vertices, IndexList& indices)
{
VertexList vin = vertices;
IndexList iin = indices;
vertices.resize(0);
indices.resize(0);
// v1
// *
// / \
// / \
// m0*-----*m1
// / \ / \
// / \ / \
// *-----*-----*
// v0 m2 v2
UINT numTris = (UINT)iin.size()/3;
for(UINT i = 0; i < numTris; ++i)
{
D3DXVECTOR3 v0 = vin[ iin[i*3+0] ];
D3DXVECTOR3 v1 = vin[ iin[i*3+1] ];
D3DXVECTOR3 v2 = vin[ iin[i*3+2] ];
D3DXVECTOR3 m0 = 0.5f*(v0 + v1);
D3DXVECTOR3 m1 = 0.5f*(v1 + v2);
D3DXVECTOR3 m2 = 0.5f*(v0 + v2);
vertices.push_back(v0); // 0
vertices.push_back(v1); // 1
vertices.push_back(v2); // 2
vertices.push_back(m0); // 3
vertices.push_back(m1); // 4
vertices.push_back(m2); // 5
indices.push_back(i*6+0);
indices.push_back(i*6+3);
indices.push_back(i*6+5);
indices.push_back(i*6+3);
indices.push_back(i*6+4);
indices.push_back(i*6+5);
indices.push_back(i*6+5);
indices.push_back(i*6+4);
indices.push_back(i*6+2);
indices.push_back(i*6+3);
indices.push_back(i*6+1);
indices.push_back(i*6+4);
}
}
//***************************************************************************************
// Name: BuildGeoSphere
// Desc: Function approximates a sphere by tesselating an icosahedron.
//***************************************************************************************
void BuildGeoSphere(UINT numSubdivisions, float radius, VertexList& vertices, IndexList& indices)
{
// Put a cap on the number of subdivisions.
numSubdivisions = Min(numSubdivisions, UINT(5));
// Approximate a sphere by tesselating an icosahedron.
const float X = 0.525731f;
const float Z = 0.850651f;
D3DXVECTOR3 pos[12] =
{
D3DXVECTOR3(-X, 0.0f, Z), D3DXVECTOR3(X, 0.0f, Z),
D3DXVECTOR3(-X, 0.0f, -Z), D3DXVECTOR3(X, 0.0f, -Z),
D3DXVECTOR3(0.0f, Z, X), D3DXVECTOR3(0.0f, Z, -X),
D3DXVECTOR3(0.0f, -Z, X), D3DXVECTOR3(0.0f, -Z, -X),
D3DXVECTOR3(Z, X, 0.0f), D3DXVECTOR3(-Z, X, 0.0f),
D3DXVECTOR3(Z, -X, 0.0f), D3DXVECTOR3(-Z, -X, 0.0f)
};
DWORD k[60] =
{
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
};
vertices.resize(12);
indices.resize(60);
for(int i = 0; i < 12; ++i)
vertices[i] = pos[i];
for(int i = 0; i < 60; ++i)
indices[i] = k[i];
for(UINT i = 0; i < numSubdivisions; ++i)
Subdivide(vertices, indices);
// Project vertices onto sphere and scale.
for(size_t i = 0; i < vertices.size(); ++i)
{
D3DXVec3Normalize(&vertices[i], &vertices[i]);
vertices[i] *= radius;
}
}
void RenderingEngine::GenerateTriangleIndices(size_t lineCount,
IndexList& triangles) const
{
size_t destVertCount = lineCount * 8;
triangles.resize(lineCount * 18);
IndexList::iterator triangle = triangles.begin();
for (GLushort v = 0; v < destVertCount; v += 8) {
*triangle++ = 0 + v; *triangle++ = 1 + v; *triangle++ = 2 + v;
*triangle++ = 2 + v; *triangle++ = 1 + v; *triangle++ = 3 + v;
*triangle++ = 2 + v; *triangle++ = 3 + v; *triangle++ = 4 + v;
*triangle++ = 4 + v; *triangle++ = 3 + v; *triangle++ = 5 + v;
*triangle++ = 4 + v; *triangle++ = 5 + v; *triangle++ = 6 + v;
*triangle++ = 6 + v; *triangle++ = 5 + v; *triangle++ = 7 + v;
}
}
