A matrix stack provides a way to apply local transforms to individual objects in our scene while at the same time we keep the global transform (camera transform) coherent for all of them. Let's see how it works.
Each rendering cycle (each call to our draw function) requires calculating the scene matrices to react to camera movements. We are going to update the Model-View matrix for each object in our scene before passing the matrices to the shading program (as attributes). We do this in three steps as follows:
Step 1: Once the global Model-View matrix (camera transform) has been calculated, we proceed to save it in a stack. This step will allow us to recover the original matrix once we had applied to any local transforms.
Step 2: Calculate an updated Model-View matrix for each object in the scene. This update consists of multiplying the original Model-View matrix by a matrix that represents the rotation, translation, and/or scaling of each object in the scene. The updated Model...