[ quesa-Bugs-967958 ] Trimesh transparency vertex attributes not applied properly

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Bugs item #967958, was opened at 2004-06-06 22:40
Message generated for change (Comment added) made by jwwalker
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Category: None
Group: None
>Status: Closed
>Resolution: Rejected
Priority: 5
Private: No
Submitted By: Frank Condello (pox)
Assigned to: Nobody/Anonymous (nobody)
Summary: Trimesh transparency vertex attributes not applied properly

Initial Comment:
Transparency color vertex attributes in a trimesh do not appear to 
properly flag all vertices/triangles as transparent.

This screenshot: <http://webhome.idirect.com/~frankco/
transerror.jpg> shows a heightmap that has been flooded with 
transparency color vertex attributes and should draw entirely in 
the transparent color, but it appears that (possibly) every-other 
triangle is solid. The same model works as expected in QD3D.

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>Comment By: James W. Walker (jwwalker)
Date: 2007-02-27 21:05

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Since the requested sample file was never provided, I'm going to close
this.  By the way, I think that the new OpenGL renderer would not have such
a problem; vertex transparency would cause a TriMesh to be decomposed into
triangles.

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Comment By: Frank Condello (pox)
Date: 2004-06-16 14:15

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I think I've isolated the issue...

When ir_geom_trimesh_build_transparent checks for transparent vertices 
it flags transparent triangles by running through all the vertices and 
finding their parent triangle. However, ir_geom_trimesh_build_triangles 
only assigns the first triangle that references a given vertex as a
parent, 
potentially leaving some "childless" triangles in the mix. The diagram 
below illustrates a tristrip that would exhibit this bug (hopefully my
ASCII 
art comes out ok):

A-----B
|\    |\
| \ 3 | \
|  \  |  \
| 1 \ | 2 \
|    \|    \
C-----D-----E

vertex A parent = triangle 1
vertex B parent = triangle 2
vertex C parent = triangle 1
vertex D parent = triangle 1
vertex E parent = triangle 2

ir_geom_trimesh_build_transparent won't flag triangle #3 as transparent 
in this case, even if all it's vertices are transparent.

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Comment By: Dair Grant (grantd)
Date: 2004-06-15 17:15

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Can you attach the model to this bug, or make it available?

The list of transparent triangles is constructed in 
ir_geom_trimesh_build_transparent: do you see anything odd if you step 
through there? Also, does the TriMesh have a usage array for this vertex 
attribute?

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