void GeometryGenerator::CreateCylinder(float bottomRadius, float topRadius, float height, UINT sliceCount, UINT stackCount, MeshData& meshData)
{
meshData.Vertices.clear();
meshData.Indices.clear();
//
// Build Stacks.
//
float stackHeight = height / stackCount;
// Amount to increment radius as we move up each stack level from bottom to top.
float radiusStep = (topRadius - bottomRadius) / stackCount;
UINT ringCount = stackCount+1;
// Compute vertices for each stack ring starting at the bottom and moving up.
for(UINT i = 0; i < ringCount; ++i)
{
float y = -0.5f*height + i*stackHeight;
float r = bottomRadius + i*radiusStep;
// vertices of ring
float dTheta = 2.0f*XM_PI/sliceCount;
for(UINT j = 0; j <= sliceCount; ++j)
{
Vertex vertex;
float c = cosf(j*dTheta);
float s = sinf(j*dTheta);
vertex.Position = XMFLOAT3(r*c, y, r*s);
vertex.TexC.x = (float)j/sliceCount;
vertex.TexC.y = 1.0f - (float)i/stackCount;
// Cylinder can be parameterized as follows, where we introduce v
// parameter that goes in the same direction as the v tex-coord
// so that the bitangent goes in the same direction as the v tex-coord.
// Let r0 be the bottom radius and let r1 be the top radius.
// y(v) = h - hv for v in [0,1].
// r(v) = r1 + (r0-r1)v
//
// x(t, v) = r(v)*cos(t)
// y(t, v) = h - hv
// z(t, v) = r(v)*sin(t)
//
// dx/dt = -r(v)*sin(t)
// dy/dt = 0
// dz/dt = +r(v)*cos(t)
//
// dx/dv = (r0-r1)*cos(t)
// dy/dv = -h
// dz/dv = (r0-r1)*sin(t)
// This is unit length.
vertex.TangentU = XMFLOAT3(-s, 0.0f, c);
float dr = bottomRadius-topRadius;
XMFLOAT3 bitangent(dr*c, -height, dr*s);
XMVECTOR T = XMLoadFloat3(&vertex.TangentU);
XMVECTOR B = XMLoadFloat3(&bitangent);
XMVECTOR N = XMVector3Normalize(XMVector3Cross(T, B));
XMStoreFloat3(&vertex.Normal, N);
meshData.Vertices.push_back(vertex);
}
}
// Add one because we duplicate the first and last vertex per ring
// since the texture coordinates are different.
UINT ringVertexCount = sliceCount+1;
// Compute indices for each stack.
for(UINT i = 0; i < stackCount; ++i)
{
for(UINT j = 0; j < sliceCount; ++j)
{
meshData.Indices.push_back(i*ringVertexCount + j);
meshData.Indices.push_back((i+1)*ringVertexCount + j);
meshData.Indices.push_back((i+1)*ringVertexCount + j+1);
meshData.Indices.push_back(i*ringVertexCount + j);
meshData.Indices.push_back((i+1)*ringVertexCount + j+1);
meshData.Indices.push_back(i*ringVertexCount + j+1);
}
}
BuildCylinderTopCap(bottomRadius, topRadius, height, sliceCount, stackCount, meshData);
BuildCylinderBottomCap(bottomRadius, topRadius, height, sliceCount, stackCount, meshData);
}
void GeometryGenerator::CreateCylinder(float bottomRadius, float topRadius, float height, UINT sliceCount, UINT stackCount, MeshData& meshData)
{
meshData.Vertices.clear();
meshData.Indices.clear();
float stackHeight = height / stackCount;
float radiusStep = (topRadius - bottomRadius) / stackCount;
UINT ringCount = stackCount+1;
for(UINT i = 0; i < ringCount; ++i)
{
float y = -0.5f*height + i*stackHeight;
float r = bottomRadius + i*radiusStep;
float dTheta = 2.0f*XM_PI/sliceCount;
for(UINT j = 0; j <= sliceCount; ++j)
{
Vertex vertex;
float c = cosf(j*dTheta);
float s = sinf(j*dTheta);
vertex.Position = glm::vec3(r*c, y, r*s);
vertex.TexC.x = (float)j/sliceCount;
vertex.TexC.y = 1.0f - (float)i/stackCount;
vertex.TangentU = glm::vec3(-s, 0.0f, c);
float dr = bottomRadius-topRadius;
glm::vec3 bitangent(dr*c, -height, dr*s);
glm::vec3 T = vertex.TangentU;
glm::vec3 B = bitangent;
glm::vec3 N = glm::normalize(glm::cross(T, B));
vertex.Normal = N;
meshData.Vertices.push_back(vertex);
}
}
UINT ringVertexCount = sliceCount+1;
for(UINT i = 0; i < stackCount; ++i)
{
for(UINT j = 0; j < sliceCount; ++j)
{
meshData.Indices.push_back(i*ringVertexCount + j);
meshData.Indices.push_back((i+1)*ringVertexCount + j);
meshData.Indices.push_back((i+1)*ringVertexCount + j+1);
meshData.Indices.push_back(i*ringVertexCount + j);
meshData.Indices.push_back((i+1)*ringVertexCount + j+1);
meshData.Indices.push_back(i*ringVertexCount + j+1);
}
}
BuildCylinderTopCap(bottomRadius, topRadius, height, sliceCount, stackCount, meshData);
BuildCylinderBottomCap(bottomRadius, topRadius, height, sliceCount, stackCount, meshData);
}
