Using Matrix Multiplication to Rotate a cube in opengl

Question

I have some code that draws a cube. I've managed to rotate the cube using glRotatef but I need to be able to rotate the cube using only matrix multiplication. I know what matrices to use but I'm not sure how to apply them to the vertices of the cube. Is there a way to pass a vector to glVertex3f? Or a way to pass an array of vertices?

Answer 1

The OpenGL functions you're using are for immediate-mode rendering, and the vertex transformations are done within OpenGL. If you want to manually transform the vertices outside of OpenGL, you'll have to either implement matrix * vector multiplication, or use a library that does this for you.

As a side note, if you're just interested in rotation, you may find Rodrigues' rotation formula easier to implement than general matrix transformation.

Answer 2

I agree completely with Drew's answer. However, I figured I'd point you in the direction of a nicely-written tutorial series that shows these concepts in action:

http://en.wikibooks.org/wiki/OpenGL_Programming

Start with the first 3 tutorials to learn shader basics, and then the 4th and 5th tutorials dive into rotation with triangles and cubes. Also, the examples use FreeGLUT, which is a framework that allows you to easily interact with your code using key presses, mouse movements, mouse presses, and more.