I am trying to transform a triangle in 3 space with the constraint that z = 1-x-y. At this point I have the following transformation matrix A, and three vector equations: | a1 a2 a3 | A = | a4 a5 a6 | | a7 a8 a9 | A*x1 = k1*y1 A*x2 = k2*y2 A*x3 = k3*y3 I know the vertices of both triangles, before and after the transformation. The problem is that I can't put the above description in a manner that is solveable....without some input to clarify the issue. The transformed triangle points can move in a manner to suggest stretching and translation, but not rotation. Given that z is dependent on x and y, how can I constrain this problem such that I can generate n equations in n unknowns?