It turns out that the box trace CAN get out of the solid from that location
(though a similar point trace can not). This is because of my decision to
allow non-points to touch a plane from either side without crossing the
plane, whereas a point touching a plane is always considered to be on the
front side of the plane as there is no further information to disambiguate
on which side of the plane the point is.
The trace is moved as far into the leaf as possible without leaving the
other side of the leaf. This ensures that trace_contents is started from a
good location. There is currently a problem with traces that stradle a
plane getting, but this has cleared up all the current contents related
tests.
When visiting a leaf in box mode, use trace_contents() to get the highest
priority contents of any leafs touched by the box in the current location.
I'm now down to one failing test case, and it's an "allsolid" issue that
might be an incorrect assumption in my test case.
If trace is null or point type, or the hull doesn't have portals, or the
first node is a leaf, MOD_HullContents operates in point mode (exactly the
same way as SV_HullPointContents()). However, in box mode, all leafs
touched by the trace are checked for their contents. The contents field of
trace (a bit field) will indicate the contents type of all touched leafs.
The returned contents value indicates the most important contents:
solid > lava > slime > water > empty
The one's complement value of the contents type is the bit number of the
contents bit field. I'm not sure how useful this will be as getting the
amount of overlap is currently not supported.
The code itself seems to work now. There are still some problems: the box
faces are using unit vectors for the edges, or I should go back to unit
vectors for the portal edges; starting in a solid corner won't always work;
etc. However, that's just mopping up: the main algorithm seems to be
working.
When the portals are too big, floats break down and break the tests. This
might not be much of an issue in real maps, but my tests use "infinite"
planes.
Unfortunately, Pythagorus and binary don't play well together, so rounding
errors are inevetible when testing with a slope. However, 1e-6 seems to be
a good epsilon (printf's %g hides it nicely :).
If the trace hits a portal on the plane that brought us to the leaf, then
we actually are in the leaf (otherwise, we shouldn't be here and thus
should ignore the leaf). At least, that's my thinking.
Many point tests fail (but they're really using box clipping with a zero
sized box) and two box tests fail.
