Start block shapes

TODO.txt

@@ -1,3 +1,10 @@
+- sky images could be just composed of 4x4 normal images? then we only need
+  one type of image
+- map actually in ASCII format? how will humans edit it?
+- make a simple rendering setting:
+  - will exclude images and only draw solid colors, let's say only 16, so that
+    memory usage is reduced, CPU rendering is relieved, executable is smaller
+    AND frontend doesn't have to use RGB565 (it can basically choose any mode).
 - background sky rendering efficiently:
   - first draw the solid color top and bottom
   - then render the 3D scene
@@ -42,7 +49,7 @@ TOTAL SIZE OF TEXTURES:
   - possibility of simple procedural textures to save space! <-- SOUNDS NICE
   - possibility to turn off textures completely <-- MUST HAVE
   - how to map textures to blocks?
-    - figured out nice procedural mapping in Blender :)
+    - figured out nice procedural mapping in Blender :) <-- DONE
   - PROBABLY LIKE THIS:
     - background textures: 128x128 with image-specific 256 color palette,
       pixel access shouldn't be as time critical here (128x128/256 looks better
@@ -54,6 +61,20 @@ TOTAL SIZE OF TEXTURES:
   CAUSE BACKGROUND WON'T BE A 3D MODEL
 - Track model has to be preprocessed, unseen walls must be removed else would
   be too slow. <-- OF COURSE
+  - Removing unseen triangles:
+    - make a routine that does the cleaning, call it several times during the
+      model construction (waiting till the very end could run out of memory
+      with too many vertices/triangles, also processing so many of them could
+      even make it slower), it will work like this:
+      - go through all triangles, mark each covered or not (we can't remove
+        them right away, they need to stay to see if they cover other tris)
+      - for each triangle go through all again, mark the checked tri covered if:
+        - the other tri has the same vertices (trivial case), OR
+        - non-trivial case (consider e.g. two covering quads but split
+          differently) not so easy, maybe good enough: if the tris share two
+          vertices AND they're in the same plane (EZ to check for axis aligned)
+          AND the other tri has a neighbor tri that has the non-shared vertex?
+      - remove all marked tris AND vertices that become unused
 - ====== Track/map format: list of map blocks. =======
   - one block record:
     - type: 5 bits?