Rotation by an angle θ (in radians) around an axis (unit-length vector) [u, v, w]T is given by:


In GLM, this is programmed with the command:

mModelMatrix = glm::rotate(mModelMatrix, angle, glm::vec3(x, y, z));

Angle is expressed in degrees; rotation is counter-clockwise around a vector [x, y, z]T. 



Example:
Suppose we have a point p = [x, y, z]T.  First, we homogenise p so that p = [x, y, z, 1]T.

Now, let’s determine the matrix product Rp, where R is a rotation about the z-axis:

High