optimize.txt

Obvious open optimizations:

texture mapper speedup
  - assembly affine-span drawer
  - optimize perspective math to compute less stuff
  - overlap perspective divide (and write outer perspective loop in assembly)
  - combine out perspective loop and inner affine loop together

reduce overdraw
  - span clipper or edge-table system

other inner loops
  - assembly surface builder
  - assembly scan conversion

outer rendering traversals
  - mark nodes with visible faces (need face->node mapping; see design.txt)
  - PVS data is an RLE bit-array, which I decode into a non-RLE bit-array.
    This decoding would be much faster if the alignment of the bit-arrays
    were different.
  - precompute node-PVS data, and encode in BSP-order (see design.txt); then
    the current first two steps (decode leaf PVS and propogate up BSP tree)
    can be a single step which only visits as much of the tree as is visible,
    instead of the whole things.