Hi guys, I'm return witho other trouble... First of all, I've changed the code of the Nehe's Lesson 27 for drawing the shadow; in this mode I don't have the problem of the z-pass algorithm. I use z-fail algorithm. But where is the shadow (or the shadowing quad) there are some artifacts like z-fighting!!! here there is a screenshots of my problem: biobrain.altervista.org/Grafica/ScreenShots/artefatti.JPG I tried to use the same technic of the tutorial, but the problem is there. The real tutorial,instead, don't have some problem. Help me!!! ^_^