Consider a monochrome ball. The colours of the pixels is a function of the point height, the light intensity, the light angle, and the surface material (reflection).
What is the simplest formula defining the resulting gradient?
Note that my question is not about raytracing, as we assume a simple object with no inner shadow/reflection. I am just curious what is the simplest relation between the pixel colour and the four parameters (of if there are more).
For every point, we have the coordinate
(x,y,z) and the RGB colour of the material (left image). How can we calculate the appearance colour (the right image) in a very basic form?