The fragment shader expects a normal, but the vertex shader was not providing one.
Fix: added a new vertex shader that has normals + smooth color interpolation.
I also split gpu_shader_3D_vert in two:
- one with just position
- one with position + normal
For each of the builtin shaders, we should be able to look at the GLSL and tell exactly what it's doing. Using #defines and #ifdefs for rendering options makes the shaders hard to read and easy to break.
8dcf7a46a2