Subject:
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Re: 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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Thu, 30 Sep 1999 23:25:22 GMT
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Viewed:
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626 times
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Jean-Pierre PARIS wrote in message <37F3B871.74AE196F@wanadoo.fr>...
> ...
> Here is a rough sketch of my algorithm. It's based on ray tracing too.
> But, the algorithm presented by Gary has a major problem: it supposes
> that the part IS a real solid, and this is not always the case. For some
> parts, the quads/triangles did not sit exactly aside because of number
> rounding problems.
> ...
My algorithm doesn't require the vertices to exactly match; I was intending
to pass one ray per polygon through the dat object, not an arbitrarily large
number. And only if a ray penetrated an even number of polygons would those
polygons be automatically processed.
> ...
> 7. Once this poly is oriented, you can also orient all the polys that
> are connected to it (and so on): two connected polys share one edge.
> This edge orientation is opposite in the tow polys.
> 8. Repeat from step 1 until all polys are oriented.
> ...
That's a clever algorithm.
Assuming (after all close vertices are matched up) that no polygons have
zero neighbors, after determining the orientation of one polygon, you could
visit each neighboring polygon (somewhat like a flood fill algorithm) and
determine its orientation easily. Only one ray would be needed in the
entire process.
-Gary
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