Re: Surface detail polygons?

Bernie Roehl ([email protected])
Fri, 24 Nov 1995 15:19:58 -0500


Hans Holten-Lund writes:
> I was wondering how we are supposed to cesate surface detail
> polygons in VRML.

You can't, unfortunately.

> Such polygons are *ATTATCHED* to a parent polygon, and are
> drawn on top of the parent polygon, if it is not back-face
> culled.

Yes, they're a good idea both for performance reasons and to avoid
problems with shallow Z-buffers.

> Attatched polygons are available in Lightwave and the old
> Videoscape3D

And in Superscape, and probably lots of others as well. Not sure how the
converters handle this case; the best they could probably do is to move
the detail polys along their normal by some small (user-settable?) amount.

The problem is that if the amount is too big you get the "windows floating
in front of the wall" effect you described in your message, and if the
amount is too small you hit the resolution limits of the Z buffer and get
the nasty "smesdded polygon" effect.

-- 
   Bernie Roehl
   University of Waterloo Dept of Electrical and Computer Engineering
   Mail: [email protected]    Voice:  (519) 888-4567 x 2607 [work]
   URL: http://sunee.uwaterloo.ca/~broehl

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