abitrary axis for 2D matrix Rotation?

Question

I am having some trouble getting my matrix math correct. I have a translation, rotation, and scale matrix working properly, but I want the rotation to be about an arbitrary axis. I have found a formula for a 3D matrix, but i only have x,y,w. Any help would be greatly appreciated and needed

Answer 1

In simple terms, a rotation about an arbitrary axis is equivalent to translating that axis back to the origin, performing rotation, and then translating the axis back.

So if you have the three matrices for the three individual steps, just multiply the matrices together. (Note that this requires making the matrices compatible - you can't have a 2x2 rotation matrix - you need one that handles the same coordinate system that your translation matrices do - probably (should be?) homogeneous coordinates:

http://en.wikipedia.org/wiki/Homogeneous_coordinates
http://en.wikipedia.org/wiki/Affine_transformation

Answer 2

2d Matrix Rotation