?

I'm not sure that Collision Detection, as I know it, works that way. It's basically a rendering "intersection detection" algorithm that, when activated, will place the rendered surface in "front" of a surface that is colliding/intersecting with it. (But, only in small increments - It's a very "iffy" solution for small poke-throughs.) It works in the renderer and doesn't have an effect, that I know of (and I might be about to learn something new, here) in the Preview pane. (ie: I don't think the OpenGL renderer pays any attention to it.)

IOW - It's not really a "physical collision detector" sort of thing, unless I'm waaaay off the mark and you're talking about something else. However, if it did do something in the Preview pane, I would certain cause some extra processing. I just haven't noticed any effects, but it will slow down a render a little bit. (Don't click it on for hair models unless you've packed a lunch...) I don't know that Poser 8 has any physics modules besides that balance thingie toggle and those provided by custom python scrips.