CGTalk - Q: intersecting polygons

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earl

06-10-2003, 02:42 AM

Somebody had a thread here recently showing a SWAT officer, and the helmet was placed over the ears, creating intersecting polys. Sombody mentioned that this is bad technique. 3rd reply:

http://www.cgtalk.com/showthread.php?s=&threadid=64696

I'm an amateur modeler without the background on how PCs render game graphics, and I've used intersecting polygons a lot for weapon in mods I've made, to keep the overall poly count down. It seems even the original game weapons used the same technique - can somebody clarify for me?

Here's an example:

http://www.baconbomb.com/modworks/screens/mg3_02.jpg

http://www.baconbomb.com/modworks/screens/mg3_wire.jpg

The receiver is a basic block, and all the extra parts are seperate objects that pass through the receiver -- is this proper technique, or is it actually better to have a single but more complex mesh?

EvoG

06-10-2003, 04:08 AM

You don't neccessarily HAVE to avoid self-intersecting polys, but depth sorting errors could arise, and the slowdown is negligible if at all, and besides, since most if not all engines now use zbuffers which determines depth on the pixel level, its not a problem at all. But, just to say, you don't need self-intersecting models. You can just leave the parts of your mesh as close to flush with a surface as possible...i.e. the grip could be made to have the top edge that goes into the main body of the gun be flush with the bottom edge of the main body, rather than intersect the the base poly.

Really, don't worry about...low poly tree stand-ins are 2 polys intersecting eachother in the centers( tree top down ---> X ), so its not really a concern anymore.

Your gun looks great.

Cheers

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