1. Yes, but when matrix contains only rotations and translations (no scaling).
Uhh...:shock: why no scaling?? if you scale, you simply stretch the base vectors. So if you create a scale matrix with factors (2,2,2), the base vectors of the matrixes coordinate system will have a length of 2.
So everything transformed with this matrix will become 2 times bigger.

If you need base vectors with length=1.0 then you simply have to normalize them. isn't it?? :?

Sorry but i dont see the problem with scaling. Could you explain that??

Since the matrix is square, it can be inverted.
right... so that's the main reason why we use 4x4 matices. It can be inverted.
BTW: what's inverted?? calculating the inverse matrix?? :? didn't know a square matrix was required to do that.

So whe do not use the 4th column, except if we want to do something with W.
So if we set W to 2, would that multiply all translation valeus by 2?? can that be usefull?? :?

I like to know how the projection matrix in my first post works.. if anyone knows, please let me know.