Shadertoy shaders _do_ include the render algorithm. That shader is completely ray-traced, so the only real input that is used for that shader is the x, y coordinates and time. It's not using any of the GPU's polygon rasterization. It's stateless and is generating the terrain while it ray-traces it.

Firstly - this is really nice. I don't want to derogate the work itself in any way (and I don't think the gp did either) - I'm just really quite curious about what exactly the post title is referring to.

If I extract the code and delete what I can see might be extraneous setup boilerplate (event handling, camera navigation, init function, image download helper utility, various config object initialisations), it still comes in at around 150-200 lines. The render function alone is 38 lines, not including the external dependencies of that function (DrawVerticalLine, screen, camera).

Again, not a criticism of the work, just querying the title.

To be fair that seems to originally be a piece of the 4k demo elevated.