Calvin1602
commented
6 years ago Hi Baslack, thanks for your feedback.
The formulas you're suggestion are indeed the full Gram-Schmidt formulas, and should be correct. However, I don't think the current implementation is broken (although I admit there's a tricky shortcut) :
- By construction, t is orthogonal to n (line 37)
- By construction, b is orthogonal to n (line 38)
- The only missing part is that t should be orthogonal to b, too.
- Line 61 does just that.
Do you have a case where this breaks ? Sincerely, Arnaud
baslack
Greetings. Thanks for your work on this extensive tutorial set. I think I may have found a problem with the code performing orthogonalization of the tangent and bitangent. First, it appeared that bitangent orthogonalization was left out altogether, while the tangent operation left off part of the required calculation. To fix it I added the following function to tangentspace.cpp
glm::vec3 proj(glm::vec3 u, glm::vec3 v) { return u * (glm::dot(u, v) / glm::dot(u, u)); }
and modified the "Going Further" loop as follows:
...
t = glm::normalize(t - proj(n, t)); b = glm::normalize(b - proj(n, b) - proj(t, b)); ...
Those two together will make TBN orthogonal and allow the inverse transpose. Please correct me if you find this in error. Thanks for your attention.
-B