Directx11教程(55) 建立球形和锥形物体
Directx11教程(55) 建立球形和锥形物体“本教程中，我们新建2个model class，SphereModelClass以及CylinderModelClass,分别用来表示球形和锥形物体。
程序执行后的界面如下：
http://images.cnblogs.com/cnblogs_com/mikewolf2002/201208/201208090658289435.png
线框模式界面如下：
http://images.cnblogs.com/cnblogs_com/mikewolf2002/201208/201208090658369756.png
从线框模式可以看出，球形是由三个因素决定：半径、经度线、纬度线。
在SphereModelClass.cpp中，我们看到，初始化顶点缓冲和索引缓冲的函数为：InitializeBuffers(ID3D11Device* device, float radius, int numSlices, int numStacks)，它多了三个参数，分别表示半径、经度切片的数量、纬度切面的数量。具体构建球形顶点的操作在函数buildStacks(vertices, indices)中，主要就是把经纬度切片的数目转化成球坐标系中的角度，求出球坐标系中顶点，再转化到笛卡尔坐标系中。
代码如下：
void SphereModelClass::buildStacks(VertexList& vertices, IndexList& indices)
{
float phiStep = PI/m_NumStacks;
int numRings = m_NumStacks-1;
// 对于每个纬度环，计算顶点.
for(int i = 1; i <= numRings; ++i)
{
float phi = i*phiStep;
// 环上的顶点
float thetaStep = 2.0f*PI/m_NumSlices;
for(int j = 0; j <= m_NumSlices; ++j)
{
float theta = j*thetaStep;
VertexType v;
// 球坐标到笛卡尔坐标的转化
v.position.x = m_Radius*sinf(phi)*cosf(theta);
v.position.y = m_Radius*cosf(phi);
v.position .z = m_Radius*sinf(phi)*sinf(theta);
D3DXVec3Normalize(&v.normal, &v.position);
//球的纹理坐标
v.texture.x = theta / (2.0f*PI);
v.texture.y = phi / PI;
v.Kd = D3DXVECTOR4(0.2, 0.2, 0.1,1.0);
v.Ks = D3DXVECTOR4(0.2, 0.2, 0.2,1.0);
vertices.push_back( v );
}
}
// 球的极点: 会出现纹理坐标扭曲
VertexType t1;
t1.position = D3DXVECTOR3(0.0f, -m_Radius, 0.0f);
t1.normal = D3DXVECTOR3(0.0f, -1.0f, 0.0f);
t1.texture = D3DXVECTOR2(0.0f, 1.0f);
t1.Kd = D3DXVECTOR4(0.2, 0.2, 0.1,1.0);
t1.Ks = D3DXVECTOR4(0.2, 0.2, 0.2,1.0);
vertices.push_back( t1 );
t1.position = D3DXVECTOR3(0.0f, m_Radius, 0.0f);
t1.normal = D3DXVECTOR3(0.0f, 1.0f, 0.0f);
t1.texture = D3DXVECTOR2(0.0f, 0.0f);
vertices.push_back(t1 );
int northPoleIndex = (int)vertices.size()-1;
int southPoleIndex = (int)vertices.size()-2;
int numRingVertices = m_NumSlices+1;
// 计算索引(不考虑极点)
for(int i = 0; i < m_NumStacks-2; ++i)
{
for(int j = 0; j < m_NumSlices; ++j)
{
indices.push_back(i*numRingVertices + j);
indices.push_back(i*numRingVertices + j+1);
indices.push_back((i+1)*numRingVertices + j);
indices.push_back((i+1)*numRingVertices + j);
indices.push_back(i*numRingVertices + j+1);
indices.push_back((i+1)*numRingVertices + j+1);
}
}
//北极点索引
for(int i = 0; i < m_NumSlices; ++i)
{
indices.push_back(northPoleIndex);
indices.push_back(i+1);
indices.push_back(i);
}
//南极点索引
int baseIndex = (numRings-1)*numRingVertices;
for(int i = 0; i < m_NumSlices; ++i)
{
indices.push_back(southPoleIndex);
indices.push_back(baseIndex+i);
indices.push_back(baseIndex+i+1);
}
}
在CylinderModelClass.cpp中，我们看到InitializeBuffers(ID3D11Device* device, float topRadius, float bottomRadius, float height, int numSlices, int numStacks),它多出了5个参数，分别表示锥体的顶部圆半径、底部圆半径，高度、经度切片的数量、纬度切片的数量。
具体计算顶点缓冲和索引缓冲由个函数组成，这三个函数的具体代码请参考源文件：
buildStacks(vertices, indices);
buildTopCap(vertices, indices);
buildBottomCap(vertices, indices);
完整的代码请参考：
工程文件myTutorialD3D11_50
代码下载：
http://files.cnblogs.com/mikewolf2002/d3d1150-58.zip
http://files.cnblogs.com/mikewolf2002/pictures.zip
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