fix bugs in renderView

mat2 should applied before y,z axis flipping

If you look at the original code, world_coords[0], world_coods[1], world_coods[2] has been normalized by
world_coords[3], but itself not normalized to 1.0f. Then mat2 is applied to world_coods directly, so you will get distored result. See my closed pull request #1015. 

On the other hand, y or z axis flipping operation should be applied after mat2.