| 1 0 0 0 | | 0 1 0 0 | |-x/z -y/z 0 -1/z| | 0 0 0 1 | this projection matrix generates unexpected result, while | 1 0 0 0 | | 0 1 0 0 | |-x/z -y/z 0 0 | | 0 0 0 1 | generates the expected result. why can''t the last column be something else than (0, 0, 0, 1)''

a) it depends on what you expect.
b) it can be, if you know what you are doing (and what to expect).

i want to project some model to the xOy plane.
and i think the matrix
-z 0 0 0
0 -z 0 0
x y 0 1
0 0 0 -z
is right.
it works when i multiply vectors with the matrix myself, but generates wrong result(infinite far) when using OpenGL.
so i want to ask why and how to solve it.
(transposing is already considered)