GPU rendering of SDF CSG trees with shadows, reflections and refraction.
SDF & ray marching resource: https://www.iquilezles.org/www/articles/distfunctions/distfunctions.htm
Optimisations based on https://erleuchtet.org/~cupe/permanent/enhanced_sphere_tracing.pdf :
- Over-relaxation sphere tracing
- Screen-space aware intersection point selection
Custom optimisation of lower resolution marching & then precise marching and shading on full res (green pixels are not calculated on high res unnecessarily: