First of all, I know PB for Q3 is coming out "soon", but I have my reasons to add this.  Like HLGuard or CSGuard, I want to basically make it so players that can't be seen (behind a wall but still in the PVS) not be drawn. To do this, I am doing 9 traces from the eye to the 8 corners of the bounding box and the center of the bbox for each player. If all of these traces are unable to make it to the player, then it doesn't draw him.

However, there are transparent walls and glass that can be seen through. So if any of the traces hit a CONTENTS_TRANSLUCENT or SURF_NODRAW, it will assume the player can be seen. However, I've been told that the terrain shader sets the surfaceparm to NODRAW. Here's the basic loop check:

Code Sample

for (i =0; i < 9; i++) { CG_Trace(&trace, start, NULL, NULL, ends[i], -1, CONTENTS_SOLID); if ( trace.fraction == 1 || (trace.contents & CONTENTS_TRANSLUCENT) || (trace.surfaceFlags & SURF_NODRAW)  ) return qtrue; } return qfalse;

So how can I have it so terrain blocks my checks for player visibility if I check the surfaceflags for SURF_NODRAW?

While this doesn't help you guys on the outside, one idea that could be explored if you had the full source access it to generate a scene that has known results and have the card render it (but not display it).  Read back the frame buffer and see if it has the known results.  Do this every so often (90 seconds or so).  If something is in the image you weren't expecting, then the guy is problably cheating.

Honestly I think the trace idea is too flawed to work.  

First, 9 traces every client frame is a huge amount and in most engines will cause too much of a frame rate loss to be worth the protection.

Second, someone could just hack out the traces so it always succeeds and not only do you get cheats again but a higher frame rate.

Third, there are too many situations where all corners of the bounding box are obscured.  Like, a small window, or a railing/fence, etc..  You would undoubtably have situations where someone is invisible because the traces cant find them.

Ricks idea is really the best way to go, but again is prone to being hacked itself.  Really, anything you do it will only be a short matter of time before someone breaks it again.  Thats why evenbalance exists.  They dont just sell the punkbuster technology, they sell a service which is to keep on top of the cheats and erradicate them when they pop up.  This in my opinion is the only way to handle this issue with todays technology.