features:

- scene and model rendering strategies:
  - random (no visibility checks)
  - sorted:
    - back-to-front (slower, better memory efficiency)
    - front-to-back (faster, but needs 1bit stencil buffer)
  - Z-buffer:
    - full
    - reduced (resolution and precision)

- perspective correction modes:
  - none                                 DONE
  - full                                 DONE
  - triangle subdivision (each triangle side will be subdivided after reaching
    a defined length, which will be measured by Chebyshev or similarly fast
    distance).
  - also offer some approximation function?

- predefined 3D shapes:
  - cube                                 DONE
  - sphere
  - cylinder
  - pyramid
  - plane

- Depth computation during rasterization -- this should be an optional thing,
  specified with a define (S3L_COMPUTE_DEPTH), which may be turned on
  automatically for some modes (e.g. Z-buffer). It should be computed by the
  fast lerp and passed in the PixelInfo struct.
- Python tool to convert obj to C array
- helper functions for lighting/shading
- Line and point drawing modes for triangles should maybe not overlap on
  adjacent triangles (as filled triangles already do)?
- create demos

bugs:

repeated:

- valgrind (and similar) checks
- optimize
- write tests/benchmarks