In the end, the coefficients were right. For the sake of completeness, here's a, b and c of the quadratic.


a = (A-D)⊗(C-B)
b = (M-A)⊗(A-D+C-B) + (A-D)⊗(B-A)
c = (M-A)⊗(B-A)

Here's a pic showing the texture coords at work.


I must've messed up the code previously, because it worked, we presented our work on Thursday and the professor was very pleased :D.

Here's a couple of pictures of our resulting work.





Thanks a lot for all your help!


Diego

I know this is a VERY old thread, but I encountered this problem as well and found the only solution here.
Unfortunately, I think erissian's formula is flawed. There is a small error which kept me busy for a while, but I solved it and thought I could share the solution:

erissian wrote:
M[sub]x[/sub] = (1-s)A[sub]x[/sub] + st(A-D+C-B)[sub]x[/sub] - t(A-D)[sub]x[/sub]
M[sub]y[/sub] = (1-s)A[sub]y[/sub] + st(A-D+C-B)[sub]y[/sub] - t(A-D)[sub]y[/sub]

But it should be:
M[sub]x[/sub] = [color=#ff0000]sB[sub]x[/sub]+(1-s)A[sub]x[/sub] + st(A-D+C-B)[sub]x[/sub] - t(A-D)[sub]x[/sub]
M[sub]y[/sub] = [color=#ff0000]sB[sub]y[/sub]+(1-s)A[sub]y[/sub] + st(A-D+C-B)[sub]y[/sub] - t(A-D)[sub]y[/sub]

This simplifies to these coefficients of the quadratic equation at[sup]2[/sup] + bt + ct = 0
a = C?D+D?B+A?C+B?A
b = M?C+D?M+B?M+M?A+C?A+B?D+2(A?B)
c = M?B+A?M+B?A

I don't know if these are the same values diegovar calculated in the end, but they work