Re: OBJ loader or pfdBuilder question

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Sharon Clay (src++at++rose.engr.sgi.com)
Thu, 11 Sep 1997 22:34:21 -0700

+>---- On Sep 11, 4:25pm, Scott McMillan wrote:
> Subject: OBJ loader or pfdBuilder question
->
->I have an OBJ file that appears to load fine with perfly, i.e. the
->front faces across groups seems to be correct.
->
->Now I have been developing my own OBJ loader to have greater control over
->strips and though I had reasonably stable. But with this one particular
->model some of the groups have the normals reversed (back and front have been
->reversed).
->
->Now I am used to Alias screwing up the normals on entire groups, and I am
->trying to figure out whether the (1) OBJ file is messed up or (2) my code has
->a bug.
->
->My question involves the former case: during pfLoadFile_obj, does the
->pfdBuilder code (or whatever) check to see if the assigned normals are
->consistent with the CCW order of the vertices of the triangles, and if it
->detects an inconsistency does it reverse the normals?

The AUTO_ORIENT Builder/GeoBuilder mode does this.
there is also ORIENT_VERTICES to give the normal priority and
re-order the verticies. Then there is ORIENT_PRESERVE to tell
us to keep our paws off. The default is ORIENT_VERTICES so if
Alias flipped your normals, we would flip the verts to match.

src.

-- 
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Sharon Rose Clay (Fischler) - Silicon Graphics, Advanced Systems Dev.
src++at++sgi.com  (415) 933 - 1002  FAX: (415) 965 - 2658  MS 8U-590
-----{-----{---++at++   -----{----{---++at++   -----{----{---++at++   -----{----{---++at++
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