I am working with openGL ES 2.0. I have checked on The Matrix and Quaternions FAQ what I want to do, but I couldn’t find it. I have 2 rotation matrix. First, I have a 4x4 matrix that orientates the model in the space. I got the matrix from a library, so I do not have the single angles. Then, I have a rotation matrix to make my own rotations. However, I have realised I cannot simply multiply them, as I want to apply both rotations with the original coordinate system. In other words, if I apply one of the two matrices work as expected as it rotates from the original coordinates system. However, If I apply both, the second rotation use the coordinate system modified by the first matrix.
Is it a way to add both matrices?