PDA

View Full Version : matrix problem



miko
02-27-2003, 01:12 AM
i've got a trnasformation matrix and i've got coordinates of vetex after that matrix has been applied on it. is it possible to doetermine original vertex coordinates?

roffe
02-27-2003, 01:24 AM
v' = Mv
v = M^-1 * M * v

If your transformation matrix is non-singular(determinant != 0) then yes. Determining the inverse can be difficult though. It all depends what you start out with...

MichaelNewman
02-27-2003, 03:07 PM
I think the above should be:

u - initial position
v - final position

v = M * u
u = M^-1 * v

Determining the inverse of a matrix is a rather complicated process. Try to google it and look for the formula based on Cramer's rule. Keep in mind that calculating the inverse of a matrix is really computationally expensive and so you don't want to do it too often.

miko
02-27-2003, 03:22 PM
yeah, everything works cool... all needed inverse matrices are computed during initialization so ist's pretty fast