On Fri, 29 Jun 2007, Eduardo Sanz-Garcia wrote:
I am getting the rotation matrices (I am not interested in the translation column) using matrixget command. My naive question: Should I use in this way:
x' x y' = [3x3 matrix] y z' z
or in this other way?
z' z y' = [3x3 matrix'] y x' x
Thank you very much.
It's the first way. The coordinate system is right-handed with column vectors for Points and Vectors (eg., normals) which would be on the right hand side of the matrix matrixset/matrixget uses. An additional row of [0 0 0 1] could be added on if you wanted a 4x4 matrix. For Point or Vector transformations, Points have an implicit forth value of one: Px' R00 R01 R01 Tx Px Py' = R10 R11 R12 Ty * Py Pz' R20 R21 R22 Tz Pz 1 And Vectors and an implicit forth value of zero: Vx' R00 R01 R01 Tx Vx Vy' = R10 R11 R12 Ty * Vy Vz' R20 R21 R22 Tz Vz 0 So Vector transformations ignore the translation part. Greg Couch UCSF Computer Graphics Lab