How it works
- Create a circle of Radius R1 centred at R2
- Create a donut by rotating about the Y axis
- Spin the donut around the X and Z axes
- Pject donut onto 2D screen
- Determine illumination by calculationg surface normal (givel a light source)
the idea is taken from here https://www.a1k0n.net/2011/07/20/donut-math.html