Incomplete SURF_ALPHATEST support

[SirYodaJedi]

Issue

The new Quake II remaster (henceforth Q2EX) supports an additional surface flag (bit 25, 0x02000000) for binary transparency, as seen in Q2Pro and KMQuake2. Like SURF_TRANS33 and SURF_TRANS66, this flag needs to be used in conjunction with CONTENTS_TRANSLUCENT in order to actually allow the contained brush to be seen through.

Solution

Q2Tools-220 currently automatically flags brushes with faces containing Trans33 and Trans66 as translucent, and this function could be extended to do the same for alphatest.
I have drafted an example of what might need to be done. I don't really do much programming, so I don't completely understand everything involved, which is why this is currently labeled as incomplete and a draft. For example, there are some mentions of the translucency flags in src/patches.c that I have no clue what they do. I hope though, that as a draft, it explains well enough what should be necessary to accomplish what I am suggesting be added.

[qbism]

This is fairly straightforward to add but other support seems needed. Questions:

1. Do any existing .map files compatible with q2pro support this? What compile tools for Q2EX exist?
2. Does rad need changes? For example, when transparency mask is enabled (SURF_TRANS33 + SURF_TRANS66) rad basically passes half the light through.
3. What do these maps look like in non-supporting engines?

I am going to close this request because it is incomplete and untested, but encourage adding as a feature request to issues where it may get more visibility if others have input.