第九章：有纹理的球体、圆柱体和锥体.doc

第九章：有纹理的球体、圆柱体和锥体introduction （序）这一章我们将学习怎样创建有纹理的球体、圆柱体和锥体，我们也会为它们设置法线，这样它们就能产生正确的阴影了。而且，我们将会使所有的类都从一个基类cbase派生，这是一个能以html格式来生成记录文件的和有计算法线向量功能的类。我们这一章的例子将会含有两个圆柱体、两个圆锥体和一个简单的绕太阳旋转的地月模型。how to make a cylinder （怎样生成圆柱体）我们的圆柱体将会含有两个三角扇形，一个做顶，一个做底；它的周身将由一个三角带来完成。下图（9.1）演示了它的构成，顶点和三角形的分布；并且也演示了它的一个段上的几个顶点的法线是什么样子的。这里我们只用顶点缓冲而不用索引缓冲，原因是我们想要它的顶、底与周身相拼接的地方的一些重合顶点拥有不同的法线，如果用索引缓冲就不行了（因为它的实现是把几个重合的顶点看作一个）。fig 9.1要创建一个圆柱体我们需要指定它的分段数，在上面的图示中为8。当然，分段数越多，看起来就会越平滑（越接近圆）。我们还需要指定它的高和半径，这样它的顶点、法线、纹理坐标就都出来了。下面的代码片断能告诉你这一切是怎样完成的。bool ccylinder:updatevertices() cylinder_customvertex* pvertex; word wvertexindex = 0; int ncurrentsegment; /lock the vertex buffer if(failed(m_pvertexbuffer-lock(0, 0, (byte*)&pvertex, 0) logerror(ccylinder: unable to lock vertex buffer.); return false; float rdeltasegangle = (2.0f * d3dx_pi / m_nsegments); float rsegmentlength = 1.0f / (float)m_nsegments; /create the sides triangle strip for(ncurrentsegment = 0; ncurrentsegment x = x0; pvertex-y = 0.0f + (m_rheight / 2.0f); pvertex-z = z0; pvertex-nx = x0; pvertex-ny = 0.0f; pvertex-nz = z0; pvertex-tu = 1.0f - (rsegmentlength * (float)ncurrentsegment); pvertex-tv = 0.0f; pvertex+; pvertex-x = x0; pvertex-y = 0.0f - (m_rheight / 2.0f); pvertex-z = z0; pvertex-nx = x0; pvertex-ny = 0.0f; pvertex-nz = z0; pvertex-tu = 1.0f - (rsegmentlength * (float)ncurrentsegment); pvertex-tv = 1.0f; pvertex+; /create the top triangle fan: center pvertex-x = 0.0f; pvertex-y = 0.0f + (m_rheight / 2.0f); pvertex-z = 0.0f; pvertex-nx = 0.0f; pvertex-ny = 1.0f; pvertex-nz = 0.0f; pvertex-tu = 0.5f; pvertex-tv = 0.5f; pvertex+; /create the top triangle fan: edges for(ncurrentsegment = 0; ncurrentsegment x = x0; pvertex-y = 0.0f + (m_rheight / 2.0f); pvertex-z = z0; pvertex-nx = 0.0f; pvertex-ny = 1.0f; pvertex-nz = 0.0f; float tu0 = (0.5f * sinf(ncurrentsegment * rdeltasegangle) + 0.5f; float tv0 = (0.5f * cosf(ncurrentsegment * rdeltasegangle) + 0.5f; pvertex-tu = tu0; pvertex-tv = tv0; pvertex+; /create the bottom triangle fan: center pvertex-x = 0.0f; pvertex-y = 0.0f - (m_rheight / 2.0f); pvertex-z = 0.0f; pvertex-nx = 0.0f; pvertex-ny = -1.0f; pvertex-nz = 0.0f; pvertex-tu = 0.5f; pvertex-tv = 0.5f; pvertex+; /create the bottom triangle fan: edges for(ncurrentsegment = m_nsegments; ncurrentsegment = 0; ncurrentsegment-) float x0 = m_rradius * sinf(ncurrentsegment * rdeltasegangle); float z0 = m_rradius * cosf(ncurrentsegment * rdeltasegangle); pvertex-x = x0; pvertex-y = 0.0f - (m_rheight / 2.0f); pvertex-z = z0; pvertex-nx = 0.0f; pvertex-ny = -1.0f; pvertex-nz = 0.0f; float tu0 = (0.5f * sinf(ncurrentsegment * rdeltasegangle) + 0.5f; float tv0 = (0.5f * cosf(ncurrentsegment * rdeltasegangle) + 0.5f; pvertex-tu = tu0; pvertex-tv = tv0; pvertex+; if(failed(m_pvertexbuffer-unlock() logerror(ccylinder: unable to unlock vertex buffer.); return false; return true; 那末然后呢？锁定顶点缓冲之后我们需要计算每个段的角度，也就是用分段数来平分2xpi个弧度，它将会被保存在rdeltasegangle中，在以后定义顶点位置时将会被用到。我们为它的周身设置纹理坐标时还得计算每段的长度，也就是用分段数来平分纹理坐标的最大值1.0。然后我们还得定义它的周身。我们有一个循环，它会顺序的处理每一个分段，计算分段的顶和底的顶点的x和z值，它的y值很好计算，正的半个高度和负的半个高度就是了。我们用段的长度来计算当前段的纹理坐标。然后，我们就能定义顶和底的三角扇形了。首先我们定义它们的中心点（圆心），然后用相同的计算方法得出边缘的顶点。完成后，顶点缓冲就应该满了，我们解锁它准备渲染。how to make a cone （怎样生成圆锥体）我们的锥体将由一个三角扇形来构成底，一个三角列来构成周身。像圆柱体一样，我们需要指定它的段数、高和半径。下图（9.2）演示了它的构成方法，图中的锥体为8个段，红线演示了其中一个段的法线。我们将同时使用索引缓冲和顶点缓冲。同时，我们也设置了正确的法线，得到了正确的阴影。fig 9.2我们需要指定锥体的段数，上图中的段数为8，当然，段数越多效果越好。我们还需要指定它的高和半径，这样它的顶点、法线、纹理坐标就都出来了。下面的代码片断能告诉你这一切是怎样完成的。bool ccone:updatevertices() cone_customvertex* pvertex; word* pindices; word wvertexindex = 0; int ncurrentsegment; /lock the vertex buffer if(failed(m_pvertexbuffer-lock(0, 0, (byte*)&pvertex, 0) logerror(ccone: unable to lock vertex buffer.); return false; /lock the index buffer if(failed(m_pindexbuffer-lock(0, m_dwnumofindices, (byte*)&pindices, 0) logerror(ccone: unable to lock index buffer.); return false; float rdeltasegangle = (2.0f * d3dx_pi / m_nsegments); float rsegmentlength = 1.0f / (float)m_nsegments; float ny0 = (90.0f - (float)d3dxtodegree(atan(m_rheight / m_rradius) / 90.0f; /for each segment, add a triangle to the sides triangle list for(ncurrentsegment = 0; ncurrentsegment x = 0.0f; pvertex-y = 0.0f + (m_rheight / 2.0f); pvertex-z = 0.0f; pvertex-nx = x0; pvertex-ny = ny0; pvertex-nz = z0; pvertex-tu = 1.0f - (rsegmentlength * (float)ncurrentsegment); pvertex-tv = 0.0f; pvertex+; pvertex-x = x0; pvertex-y = 0.0f - (m_rheight / 2.0f); pvertex-z = z0; pvertex-nx = x0; pvertex-ny = ny0; pvertex-nz = z0; pvertex-tu = 1.0f - (rsegmentlength * (float)ncurrentsegment); pvertex-tv = 1.0f; pvertex+; /set three indices (1 triangle) per segment *pindices = wvertexindex; pindices+; wvertexindex+; *pindices = wvertexindex; pindices+; wvertexindex += 2; if(ncurrentsegment = m_nsegments - 1) *pindices = 1; pindices+; wvertexindex-; else *pindices = wvertexindex; pindices+; wvertexindex-; /create the bottom triangle fan: center vertex pvertex-x = 0.0f; pvertex-y = 0.0f - (m_rheight / 2.0f); pvertex-z = 0.0f; pvertex-nx = 0.0f; pvertex-ny = -1.0f; pvertex-nz = 0.0f; pvertex-tu = 0.5f; pvertex-tv = 0.5f; pvertex+; /create the bottom triangle fan: edge vertices for(ncurrentsegment = m_nsegments; ncurrentsegment = 0; ncurrentsegment-) float x0 = m_rradius * sinf(ncurrentsegment * rdeltasegangle); float z0 = m_rradius * cosf(ncurrentsegment * rdeltasegangle); pvertex-x = x0; pvertex-y = 0.0f - (m_rheight / 2.0f); pvertex-z = z0; pvertex-nx = 0.0f; pvertex-ny = -1.0f; pvertex-nz = 0.0f; float tu0 = (0.5f * sinf(ncurrentsegment * rdeltasegangle) + 0.5f; float tv0 = (0.5f * cosf(ncurrentsegment * rdeltasegangle) + 0.5f; pvertex-tu = tu0; pvertex-tv = tv0; pvertex+; if(failed(m_pvertexbuffer-unlock() logerror(ccone: unable to unlock vertex buffer.); return false; if(failed(m_pindexbuffer-unlock() logerror(ccone: unable to unlock index buffer.); return false; return true; 生成圆锥体的方法与生成圆柱体的方法是相似的，具体的细节你可以直接去读源代码，这里就不再罗嗦了。how to make a sphere （怎样生成球体）我们的球体是由一个三角列构成的。我们需要指定它的环数和段数，当然，环数与段数越多，它看起来就越光滑。我们将会使用索引缓冲和顶点缓冲。下图（9.3）演示了它的构成方法。fig 9.3要创建球体我们可以使用下面的代码片断，它出自gamed的dx论坛，是 “laurent” 贴的一个例子的改编。 在此我要感谢他，允许我在本directx 教程中使用他的这段代码。如果你想看那个帖子的全部内容，请到/community/forums/topic.asp?topic_id=85779。bool csphere:updatevertices() /code adapted from a sample by laurent posted on the gamed directx forum //community/forums/topic.asp?topic_id=85779 word* pindices; sphere_customvertex* pvertex; word wvertexindex = 0; int ncurrentring; int ncurrentsegment; d3dxvector3 vnormal; /lock the vertex buffer if(failed(m_pvertexbuffer-lock(0, 0, (byte*)&pvertex, 0) logerror(csphere: unable to lock vertex buffer.); return false; /lock the index buffer if(failed(m_pindexbuffer-lock(0, m_dwnumofindices, (byte*)&pindices, 0) logerror(csphere: unable to lock index buffer.); return false; /establish constants used in sphere generation float rdeltaringangle = (d3dx_pi / m_nrings); float rdeltasegangle = (2.0f * d3dx_pi / m_nsegments); /generate the group of rings for the sphere for(ncurrentring = 0; ncurrentring m_nrings + 1; ncurrentring+) float r0 = sinf(ncurrentring * rdeltaringangle); float y0 = cosf(ncurrentring * rdeltaringangle); /generate the group of segments for the current ring for(ncurrentsegment = 0; ncurrentsegment x = x0; pvertex-y = y0; pvertex-z = z0; pvertex-nx = vnormal.x; pvertex-ny = vnormal.y; pvertex-nz = vnormal.z; pvertex-tu = 1.0f - (float)ncurrentsegment / (float)m_nsegments); pvertex-tv = (float)ncurrentring / (float)m_nrings; pvertex+; /add two indices except for the last ring if(ncurrentring != m_nrings) *pindices = wvertexindex; pindices+; *pindices = wvertexindex + (word)(m_nsegments + 1); pindices+; wvertexindex+; if(failed(m_pindexbuffer-unlock() logerror(csphere: unable to unlock index buffer.)