Ello, wonder if anyone could help me. I''m pretty good at maths but unfortunately my screwed up Maths syllabus meant that at no point have I studied matrices and I fear that they may hold the answer to this question. I have a 3d object for which I have a struct containing its X, Y and Z positions and its X, Y and Z rotations (relative to the global axis). I want to rotate it along *ITS* X or Y axis (that is to rotate on its Y axis would be to turn left or right as it sees) and yet for the data in the struct to be kept correct. I know that I could apply the X Y and Z rotations to the rotation matrix and then apply the rotation that I want but I don''t know how to extract the result out and update the struct with it. Thanks very much Ian (By the way, if any people know of a good ''Maths for 3d programming'' website then a URL would be greatly appreciated!)

You should perhaps take a look at quaternions. As far as I know they are often used for this kind of rotation.
In the the articles section of gamedev are some articles about matrices and quaternions. You could take a look at
http://www.gamedev.net/reference/articles/article1691.asp.
Its an FAQ about Matrices/Quaternions.

[edited by - Roland on August 17, 2003 1:34:55 PM]