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2007年11月17日
 恢复CEGUI渲染状态
刚刚接触CEGUI，在原D3D程序上画了一个小窗口后，发现渲染效果于以前的大相径庭，查看了源代码后发现，原来CEGUI在渲染后并没有恢复到默认的渲染状态，于是改之，再编译、运行、一切正常。。。
下面是恢复其渲染状态的代码，与初始化渲染状态函数initPerFrameStates()对应
1  void DirectX9Renderer::UnitFrameStates()
2    {
3  // setup vertex stream
4
5 d_device -> SetFVF(NULL);
6
7 // set device states
8 d_device -> SetRenderState(D3DRS_ZENABLE, D3DZB_TRUE);
9 d_device -> SetRenderState(D3DRS_FILLMODE, D3DFILL_SOLID);
10 d_device -> SetRenderState(D3DRS_ALPHATESTENABLE, FALSE);
11 d_device -> SetRenderState(D3DRS_ZWRITEENABLE, TRUE);
12 d_device -> SetRenderState(D3DRS_FOGENABLE, FALSE);
13 d_device -> SetRenderState(D3DRS_CULLMODE, D3DCULL_CCW);
14
15
16 // setup texture addressing settings/*
17 d_device -> SetSamplerState( 0 , D3DSAMP_ADDRESSU, D3DTADDRESS_WRAP);
18 d_device -> SetSamplerState( 0 , D3DSAMP_ADDRESSV, D3DTADDRESS_WRAP);
19
20 // setup colour calculations
21 d_device -> SetTextureStageState( 0 , D3DTSS_COLORARG1, D3DTA_TEXTURE);
22 d_device -> SetTextureStageState( 0 , D3DTSS_COLORARG2, D3DTA_CURRENT);
23 d_device -> SetTextureStageState( 0 , D3DTSS_COLOROP, D3DTOP_SELECTARG1);
24
25 // setup alpha calculations
26 d_device -> SetTextureStageState( 0 , D3DTSS_ALPHAARG1, D3DTA_TEXTURE);
27 d_device -> SetTextureStageState( 0 , D3DTSS_ALPHAARG2, D3DTA_CURRENT);
28 d_device -> SetTextureStageState( 0 , D3DTSS_ALPHAOP, D3DTOP_SELECTARG1);
29
30 // setup filtering
31 d_device -> SetSamplerState( 0 , D3DSAMP_MINFILTER, D3DTEXF_POINT);
32 d_device -> SetSamplerState( 0 , D3DSAMP_MAGFILTER, D3DTEXF_POINT);
33
34 // disable texture stages we do not need.
35 d_device -> SetTextureStageState( 1 , D3DTSS_COLOROP, D3DTOP_DISABLE);
36
37 // setup scene alpha blending
38 d_device -> SetRenderState(D3DRS_ALPHABLENDENABLE, FALSE);
39 d_device -> SetRenderState(D3DRS_SRCBLEND, D3DBLEND_ONE);
40 d_device -> SetRenderState(D3DRS_DESTBLEND, D3DBLEND_ZERO);
42  }
另外CEGUI有2种渲染模式：立即渲染和缓冲渲染。所以在这2种渲染模式结束后都需要调用上面的代码以恢复渲染状态
版权声明：本篇为原创文章，允许转载，但转载时请务必以超链接形式标明文章的原始出处和作者信息。请尊重本人的劳动成果，谢谢！
小祥的BLOG http://xfxsworld.cnblogs.com
D3D Alpha混合
Direct3D计算Alpha混合的颜色公式：
Color = ( SrcRGB * SrcK ) + ( DestRGB * DestK )
SrcRGB表示源颜色值，即将要绘制的颜色值。SrcK表示源混合系数，通常赋值为D3DBLEND_SRCALPHA，即当前绘制像素的Alpha值
DestRGB表示目标颜色值，即当前缓冲区中的颜色值。DestK表示目标系数，通常赋值为D3DBLEND_INVSRCALPHA，即1减去当前绘制像素的Alpha值
则Direct3D计算Alpha混合的颜色公式可表示为
Color = ( SrcRGB * SrcAlpha ) + ( DestRGB * ( 1 - SrcAlpha ) )
混合步骤
Alpha混合默认关闭，所以首先需要开启它
Device -> SetRenderState( D3DRS_ALPHABLENDENABLE, true );
然后设置Alpha混合系数
Device -> SetRenderState( D3DRS_SRCBLEND, D3DBLEND_SRCALPHA );
Device -> SetRenderState( D3DRS_DESTBLEND, D3DBLEND_INVSRCALPHA);
还要指定资源(材质或Alpha通道)
Alpha通道可用DirectX自带的纹理工具创建，为DDS文件
地形高度算法小结
地形一般是用网格再从高度图里读取每个顶点的高度来生成。若进一步，想实现摄像机在地形上行走的效果，就需要算出地形上任意一点的高度。总结了3个方法：
一：
《Introduction to 3D Game Programming With Directx 9.0》这本书里介绍的，利用向量来算。
1 float Terrain::GetHeight( float x, float z)
2 {
3 // Translate on xz-plane by the transformation that takes
4 // the terrain START point to the origin.
5 x = (( float )_width / 2.0f ) + x;
6 z = (( float )_depth / 2.0f ) - z;
7 // Scale down by the transformation that makes the
8 // cellspacing equal to one. This is given by
9 // 1 / cellspacing since; cellspacing * 1 / cellspacing = 1.
10 x /= ( float )_CellSpacing;
11 z /= ( float )_CellSpacing;
12 // From now on, we will interpret our positive z-axis as
13 // going in the 'down' direction, rather than the 'up' direction.
14 // This allows to extract the row and column simply by 'flooring'
15 // x and z:
16 float col = ::floorf(x);
17 float row = ::floorf(z);
18 // get the heights of the quad we're in:
19 //
20 // A B
21 // *---*
22 // | / |
23 // *---*
24 // C D
25 float A = GetHeightMapEntry(row, col);
26 float B = GetHeightMapEntry(row, col + 1 );
27 float C = GetHeightMapEntry(row + 1 , col);
28 float D = GetHeightMapEntry(row + 1 , col + 1 );
29 //
30 // Find the triangle we are in:
31 //
32 // Translate by the transformation that takes the upper-left
33 // corner of the cell we are in to the origin. Recall that our
34 // cellspacing was nomalized to 1. Thus we have a unit square
35 // at the origin of our +x -> 'right' and +z -> 'down' system.
36 float dx = x - col;
37 float dz = z - row;
38 // Note the below compuations of u and v are unneccessary, we really
39 // only need the height, but we compute the entire vector to emphasis
40 // the books discussion.
41 float height = 0.0f ;
42 if (dz < 1.0f - dx) // upper triangle ABC
43   {
44 float uy = B - A; // A->B
45 float vy = C - A; // A->C
46 // Linearly interpolate on each vector. The height is the vertex
47 // height the vectors u and v originate from {A}, plus the heights
48 // found by interpolating on each vector u and v.
49 height = A + Lerp( 0.0f , uy, dx) + Lerp( 0.0f , vy, dz);
50  }
51 else // lower triangle DCB
52 {
53 float uy = C - D; // D->C
54 float vy = B - D; // D->B
55 // Linearly interpolate on each vector. The height is the vertex
56 // height the vectors u and v originate from {D}, plus the heights
57 // found by interpolating on each vector u and v.
58 height = D + Lerp( 0.0f , uy, 1.0f - dx) + Lerp( 0.0f , vy, 1.0f - dz);
59 }
60 return height;
61 }
62
用到的2个函数
1float Terrain::Lerp(float a, float b, float t) //一个插值函数
2{
3 return (a - (a*t) + (b*t));
4}
5
6int Terrain::GetHeightMapEntry(int row, int col) //读取高度函数
7{
8 return _heightmap[row * _numVertsPerRow + col]; // 高度图数据存在_heightmap里
9}
二：
先计算出摄像机所在三角形的平面方程，然后带入摄像机的X，Z坐标，即可得高度Y
具体实现过程见http://creatorchen1984.spaces.live.com/ 《获取地形上某一点高度》，写的十分详细
三：
网上找的一个方法
假设你的地形为terrain[][];用下面的函数求出地形上点(x,z);的y值,将人物的高度加上这个y值即可.
1float GetHeight(GLfloat x, GLfloat z)
2{
3float h=0;
4float Xb,Yb;
5int Xa,Ya;
6Xa=(int)x;
7Ya=(int)z;
8Xb=x-Xa;
9Yb=z-Ya;
10float a=terrain[Xa][Ya].y;
11float b=terrain[Xa+1][Ya].y;
12float c=terrain[Xa][Ya+1].y;
13float d=terrain[Xa+1][Ya+1].y;
14h=(a*(1-Xb)+b*Xb)*(1-Yb)+(c*(1-Xb)+d*Xb)*Yb;
15return h;
16}
17
：本篇为原创文章，允许转载，但转载时请务必以超链接形式标明文章的原始出处和作者信息。请尊重本人的劳动成果，谢谢！
小祥的BLOG http://xfxsworld.cnblogs.com
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