Does anybody out there have a way of stopping particles from digging into walls if they are too close. I've tried znear... no good for particles. Anybody got the same problem and solved it?

you could trace into the particles movement direction but I wouldn'T do that.

Particle functions should be as short as possible, which includes avoiding trace and other complex functions.

In normal case it should not matter.
Even in commercial games often borads of exploding boxes and stuff just fall through the ground and disappear.

do a trace when you create the particle then delete it if it passes the distance (or make it bounce of the object).

you can't avoid particles to pass 2 walls, the only method would be to use sprites + collisions detection OR u detec if the vector is into a solid black (omg, don't ask me for the name of that function :S)

you can also use c_content for particles
if content returns IN_SOLID (something like that) you just kill them

it is faster than tracing, but I do not recommend to use it for 100000000 particles, or so(I learned the it bad way)

you could also calculate the lifespan of the particle once in the init function with a trace in the proper direction and knowing the speed of the particle that should not be a problem...