回顾下pipeline

pipeline:

 建模空间－－（世界变换）－－世界空间－－（视见变换）－－摄像头空间－－（投影变换）－－投影空间。

 

 

关于投影变换：

D3DXMatrixPerspectiveFovLH 函数

D3DXMATRIX *WINAPI D3DXMatrixPerspectiveFovLH(      



    D3DXMATRIX *pOut,
    FLOAT fovy,
    FLOAT Aspect,
    FLOAT zn,
    FLOAT zf
);

Remarks

The return value for this function is the same value returned in the pOut parameter. In this way, the D3DXMatrixPerspectiveFovLH function can be used as a parameter for another function.

This function computes the returned matrix as shown.

w       0       0               0
0       h       0               0
0       0       zf/(zf-zn)      1
0       0       -zn*zf/(zf-zn)  0
where:
h is the view space height. It is calculated from 
h = cot(fovY/2);

w is the view space width. It is calculated from
h = w / Aspect

 

-------------------------------------------

推导一个摄像机空间的点(x,y,z,1)最终要变成投影空间的点(x',y',z',1)=(ax,by,cz,1) 而a,b,c的值就是通过上面的计算矩阵计算出来的。

 

hy/z=cot(fovY/2)y/z=(z/y1)y/z=y/y1(此y/y1是缩放比，即原vertex要投影在近平面时，应该缩放的系数。)