Question

There are two methods to rotate matrices in android.opengl.Matrix class, they are:

1. static void rotateM (float[] m, int mOffset, float a, float x, float y, float z)
   Rotates matrix m in place by angle a (in degrees) around the axis (x, y, z)

2. static void setRotateM(float[] rm, int rmOffset, float a, float x, float y, float z)
   Rotates matrix m by angle a (in degrees) around the axis (x, y, z)

Here is the original ducumentation

These methods act a bit different, but I don’t understand the exact difference. Coul you explain this to me?

Answer 1

Let’s say matrix R is rotation matrix around (x,y,z) axis by angle a, then rotateM method modifies existing matrix m like this: m = R * m, but setRotateM overwrites it: m = R.