Subject:
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Hidden surface removal, and vertex order in part/primitive DAT files
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Newsgroups:
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lugnet.cad.dev
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Date:
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Sun, 26 Sep 1999 21:44:29 GMT
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Viewed:
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409 times
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I performed some hidden surface removal tests today (I should have been
working on other things, like the inventory file cleanup utility...) and it
appears that there isn't a standard order for listing vertices in DAT files
(I only tested a few elements, and my code may be flawed, so I may be
wrong).
A common technique in the rendering world is to always specify vertices of a
polygon in clockwise order (clockwise as viewed from the outside of the
polyhedra that contains it). This cuts the rendering time in half by
allowing the rendering algorithm to ignore the polygons that face away from
the observer (assuming there are no transparent polygons through which the
observer might see the backside of another polygon).
This technique can also cut in half the amount of time required to determine
which polygon the user clicked on when selecting elements in a model, since
you can't click on a polygon that's facing away from you, so half the
polygons don't need to be tested.
So...I've got half a mind to write a utility that will load every existing
part and primitive file and analyze them and automatically tweak the vertex
orders of all the polygons. But I thought I'd mention the idea first.
-Gary
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