OpenGL Programming Guide

Chapter 3Viewing

Manipulating the Matrix Stacks

The Modelview Matrix Stack

As you've seen earlier in this chapter, the modelview matrix contains the cumulative product of multiplying viewing and modeling transformation matrices. Each viewing or modeling transformation creates a new matrix that multiplies the current modelview matrix; the result, which becomes the new current matrix, represents the composite transformation. The modelview matrix stack contains at least thirty-two 4 × 4 matrices; initially, the topmost matrix is the identity matrix. Some implementations of OpenGL may support more than thirty-two matrices on the stack. You can use the query command glGetIntegerv() with the argument GL_MAX_MODELVIEW_STACK_DEPTH to find the maximum allowable number of matrices.

OpenGL Programming Guide