Hello everyone!!

This is my first post, concerning shaders…!!

After studying linear algebra, I am trying to understand how the matrix operations are implemented in the shaders’ “gl_ProjectionMatrix * gl_ModelViewMatrix * gl_Vertex” line of code, so that I know where I’m standing in terms of vertex values/positions, and what freedoms do I have if I start playing with each one of them separately

My understanding, so far:

gl_Vertex:

Absolute position of vertex in 3d Space??

If there’s an ofBox, for example, will gl_Vertex for the 6 vertices be relative to the box, or still to the world.

gl_ModelViewMatrix:

The name throws me off a little bit.

Is this the vertex in cameraSpace?

So that if:

gl_Vertex.x = 100

cam.x = -100

then the vertex final position.x = 200 (aprox).

gl_ProjectionMatrix

Camera-wise vanishing-point (or orthogonal) deformation.

In the shader, When I try: gl_ProjectionMatrix + vec4(0, 0, zValue, 0), it quickly goes off screen or off clipping. Maybe playing around at these stage of operations is just weird!! jaja!

I appreciate your help…!!

Please, let me know if I should clarify or rePhrase something.