Because you'll get W precision lost (division by ZERO)!!!
Minimum recommended near clip plane settings == 1.0
Your value of 0.1 will probably lead to Z artifacts at way to FAR Z-plane too.
Matrix used for D3DXMatrixPerspectiveFovLH:
If you look at "-zn*zf/(zf-zn)" with Znear == 0 you will get W~0. So later in pixel pipelene you Z value will be calculated as Z=Z'/W -- where Z' - is camera space Z -- so precision lost.Code: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
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