I want to map textures with correct perspective for 3D rendering. I am using barycentric coordinates to locate points on the faces of triangles. Simple affine transformation gave me that standard, weird looking result. This is what I did to correct my perspective, but it seems to have only made the distortion greater:
three triangle vertices v1 v2 v3
vertex coordinates are v_.x v_.y v_.z
texture coordinates are v_.u v_.v
barycentric coordinates corresponding to vertices are b1 b2 b3
I am trying to get the correct texture coordinates U and V
z=b1/v1.z + b2/v2.z + b3/v3.z
U=(b1*v1.u/v1.z + b2*v2.u/v2.z + b3*v3.u/v3.z) / z
V=(b1*v1.v/v1.z + b2*v2.v/v2.z + b3*v3.v/v3.z) / z
This SHOULD work shouldn’t it? Why isn’t this working?
EDIT: The response on this page looks useful, but I am unsure what the w coordinate is. Maybe somebody could just explain that, which would also likely solve my problem. http://www.gamedev.net/topic/593669-perspective-correct-barycentric-coordinates/
note: My tags were all wrong at first. That is now fixed.
Okay, this one I DID manage to solve on my own. I was dividing by the z coordinate in screen space. The solution is to divide by the homogeneous w coordinate instead.
Well, that took a while to figure out.