Approach for writing a shader of a GLSL fragment with a solid color on a triangle / face

Question

I have vertices and triangles data that contain color for each triangle (face), and not for each vertex. those. one vertex is shared by several faces, each of which has a potentially different color.

How do I approach this issue in GLSL to get a clear color assignment for each face displayed? Calculating and assigning a vertex color buffer by averaging the colors of neighboring vertex policies is quite simple, but this, of course, creates a blurry result where the colors are interpolated in the fragment shader.

What I really need does not have to be interpolated color values ​​at all, I will have about 40k triangles obscured by about 15 possible solid colors as soon as it works as intended.

Answer 1

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Answer 2

OpenGL "per-face". :

OpenGL 3.x?

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Answer 3

In addition to other answers, you could use a variable gl_PrimitiveIDthat injects a fragment into the shader (I don’t know which version) and implicitly increases for each triangle. Then you can use this to search for color (either from a 40-kilogram texture of a bunch of flowers or color indices into a 15 color color map, or just to directly calculate from a primitive id). But do not ask me about the effectiveness of this approach.