Can we input random values to render color on a cube using PyOpenGL?

Question

I have a cube that can be rotated using mouse navigation in PyOpenGL. I want to create small sections on each face of the cube and render the different sections with different colors/illumination. It is like having a certain light source and the cube is considered as a room being illuminated with the light source. How do I set my desired values for each section ? Is it possible to do so ?

I think what you are looking for is a tessellation shader, it can divide your cube mesh into pieces. — vikAy, Mar 17 '21 at 18:00

score 0 · Answer 1 · answered Mar 18 '21 at 00:09

Extend your fragment shader to expect some kind of interpolated value (Either just add "face coordinates" to your vertices that goes from 0 to 1 across the face, or by transforming your texture uv coordinates if you have them). Then you can just use if-else inside the fragment shader. i.e.

if (coords.x < 0.5 && coords.y < 0.5) // one quarter of the face
    Lightning=...
    FragColor=...
else if ...

score 0 · Answer 2 · answered Mar 19 '21 at 16:15

You could use a geometry shader and some exponential function to distribute the colors in each face. If i undertand correcltly you want something like this:

In this case you will pass the colors you want as vertex attributes for the face you want and in the geometry shader you will compute the distance from each face-vertex to the face's center. Then you will pass that distance to the fragment shader. Passing the distance to the Fshader will interpolate the value for each fragment.

Can we input random values to render color on a cube using PyOpenGL?

2 Answers2