Fix many texture bugs, access memory in increasing order everywhere

- switch z_buffer to use screen space coordinates (why does y increase
  downward!)
- extract pointless (re)calculations from inside hot loops, in
  particular from object drawing but also to the extent allowed by
  applicable law from floor and ceiling drawing

1 files changed, 0 insertions, 0 deletions

diff --git a/surfaces.png b/surfaces.png
index f699b8b..460ab23 100644
--- a/surfaces.png
+++ b/surfaces.png