Uploaded June 2020 | Updated September 2026, 2 hours ago

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The entire set of ray tracing calculations occur in the Fragment shader (OpenGL GLSL code) - therefore using the GPU.

I've designed the code to, per fragment / pixel:
- determine the correct ray for each pixel
- accept triangles (by model) to test against by using ray-triangle intersection testing
- determine whether rays hit objects, and if so, what colour should be displayed due to lighting
- but only add said colour based on the lack of any shadows that may be generated by objects obstructing those lights
- those shadows are generated taking into account the radius of the light source - producing nice looking soft shadows where applicable
- and casting ambient rays or reflection rays, to determine any 2nd / 3rd / 4th etc order shading effects for each pixel



Find the shader code (GLSL) here: github.com/s0lly/RayTracingInTheFragmentShaderGLSL - feel free to use to your heart's content.


Happy to answer any questions in the comments below!




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