Directx11教程(55) 建立球形和锥形物体

原文: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:

Directx11教程(55) 建立球形和锥形物体

线框模式界面如下:

Directx11教程(55) 建立球形和锥形物体

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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