使用Qt5 OpenGL 3.3替换glSecondaryColorPointerEXT

Question

I'm learning OpenGL with Qt5 rewriting some legacy code. They use glSecondaryColorPointerEXT(). After checking the current support for OpenGL in commonly available video cards I've selected Qt5's class QOpenGLFunctions_3_2_Core to access the OpenGL functions.

Is there an OpenGL 3.2 version or replacement method for this function?

Answer 1

In OpenGL 3.2 you should be using shaders, furthermore by this point you should avoid legacy features like gl_SecondaryColor . The appropriate replacement for secondary color in a shader-based engine is simply an additional generic vertex attribute. I explained a very similar question related to OpenGL ES 2.0, my answer there may be of some help.

In short, glVertexPointer (...) , glColorPointer (...) , glSecondaryColorPointer{EXT} (...) are all deprecated in OpenGL 3.0. In a 3.2 core context, you cannot use them at all. Thus, you need to learn shaders and glVertexAttribPointer (...) .

A vertex shader that uses "primary" and "secondary" vertex colors in core GL 3.2 would look something like this:

#version 150 core

uniform mat4 mvp;

in      vec4 vtx_pos;
in      vec4 vtx_color1;
in      vec4 vtx_color2;

out     vec4 color;

void main (void) {
  gl_Position = mvp * vtx_pos;
  color       = vtx_color1 * vtx_color2; // It is up to you to decide what to do
                                         //   with the primary and secondary
                                         //     colors, this is just for show...
}

You would supply data to vtx_pos, vtx_color1 and vtx_color2 by using glVertexAttribPointer (...) using the attribute location queried from the GLSL vertex shader (after linking). And all this completely does away with the need for a glSecondaryColorPointerEXT (...) .