[Gtkradiant] q3map2 -convert -format map - working on texture alignment

[Rudolf Polzer]

I finally could get q3map2 -convert -format map to correctly export
texture alignment... using hacky methods, but it actually works.

The big problem is: in a Q3BSP file, there is no link between brush
sides and draw surfaces. This link is only needed for the texcoords...
but these really need it.

My approach to solve this is iterating through all triangles among the
MST_PLANAR draw surfaces, and finding the one that is on the correct
plane (and correct plane normal), has the correct shader, and shares
most of the area with the winding from the brush side. So it is a rather
brute force approach... it still decompiled a map in 13 seconds with
completely correct texture alignment. In many cases there is no matching
surface, but this seems to happen only for invisible brush faces or
textures/common/* stuff (the latter don't need texture alignment
anyway).

Now there are some things that hold me off from posting the patch in its
current state... namely: I have no idea how to convert texcoords from a
triangle to the normal .map texcoord system. I tried, and gave up,
switching to the brush primitives format which is much easier to
understand for me. Once I found the matching triangle, it's then just a
matter of solving a 3x3 linear equation system using Cramer's rule. The
big problem with that is that GtkRadiant usually cannot read that
format, unless you toggle "Alternate texture projection" - in which case
it fails to load REGULAR .map files. So brush primitives map files are
highly annoying to mappers. BTW, does ZeroRadiant solve this and allow
loading both map types without having to toggle an option and restarting
Radiant? And would it hold off that patch if the resulting .map files
are no longer old-style .maps, but brush primitives .maps?

The next problem is that I haven't yet found out how to detect which
brushes are detail brushes and which aren't, so currently all get
exported as structural. This highly increases the compile times of the
resulting .map file. Any idea how I can do this?

BTW: the test map I used for this is Nexuiz's map "starship"; whose
source once got lost in a HDD crash. Decompiling and recompiling worked
fine (luckily, _keeplights was used), preserved texture alignment, and
for an odd reason, the resulting .bsp performs BETTER than the original
in DarkPlaces (in a test demo, it went up from 113.1781634fps to
148.7892154fps). The only odd thing in the resulting .map I see is that
some surfaces are oddly chopped up into triangles prisms.

The current version of the patch can be found at
http://emptyset.endoftheinternet.org/~polzer/nexuiz/q3map2-convert-map-bprimit.diff
- but I'd like to solve the remaining issues with it before I suggest it
for inclusion.

Rudolf Polzer