features:

- scene and model rendering strategies, that can be optionally selected and 
  will configure other constants (e.g. a "low memory sort strategy" will turn
  z-buffer off and turn back-to-front sorting on).

- triangle sorting:
  - back-to-front (slower, better memory efficiency)
  - front-to-back (faster, but needs 1bit stencil buffer)

- Z-buffer:
  - full                                  DONE
  - reduced (resolution and precision)    DONE
  - more reduced (4-bit)

- 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
- drawModel: create an option that would use a cache to not transform the same
  point twice
- Optional rendering stats (FPS, rendered triangles, ...).
- Change the rotations to use yaw-pitch-roll instead of extrinsic Euler angles?

bugs:

- Why is persp. correction inaccurate near the camera?

repeated:

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