projective shadows problem


I tried to use projective shadows onto my app. just wanted to know how to use them.

After a big while of studying my projective shadow-matrix, it appears that i have a matrix known everywhere to be THE projective shadow matrix.

Is it possible to have some other matrix to project shadows ?

When I render, i could have some shadows onto my ground, but on other application, i couldn’t have it: it drawn on the wrong side… some one has any idea ??