Original Post
I'm a beginner in opengl, and I enounter a problem concering about clipping space.
I calculated perspective matrix myself and passed it to vertex shader, but why triangle was visible only when the z value of vertices multiplied by my perspective matrix is positive? Since the z value range of perspective frustum [n, f] is mapped to [-1. 1] in clipping space, any -1 < z < 1 should not be clipped which is just not the case in my situation. In case that my perspective matrix is miscalculated, I directly passed vertices with -1 < z < 0 to vertex shader, still I got nothing. but it works just fine with 0 < z < 1.
I calculated perspective matrix myself and passed it to vertex shader, but why triangle was visible only when the z value of vertices multiplied by my perspective matrix is positive? Since the z value range of perspective frustum [n, f] is mapped to [-1. 1] in clipping space, any -1 < z < 1 should not be clipped which is just not the case in my situation. In case that my perspective matrix is miscalculated, I directly passed vertices with -1 < z < 0 to vertex shader, still I got nothing. but it works just fine with 0 < z < 1.
