[wanderst at yolanda.hper.indiana.edu: geomview transparency]

[munzner]

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Subject: geomview transparency
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Hi, I'm trying to use the "transparent" button on the Materials panel
in Geomview.  What I expect to be happening is not.  I am wondering if it
is my fault or "transparent" just doesn't work.  On page 25 of the Geomview
manual, section 3.6.2 "The Materials Panel" it says "Geomview does not fully
support transparency yet and on some machines (I'm on an Silicon Graphics
Indigo 2) it does not work at all."  This is why I'm not sure if I'm making a
mistake or if "transparent" just doesn't work right.

What I expect to happen is this:  I have approximately 2500 triangles in my
object.  I have a huge .off file.  In part of the .off file I have the 3
vertices for each triangle, the rgb value and an opacity value for the
triangle.
Like this:

3  2090 2091 2089 0.835294 0.929412 1.000000 1.000000

Farther down in the file, I have triangles with opacity 0.400000

Until I hit the "transparent" button on the Materials panel, everything should
look the same (totally solid, same transparency) correct?

Now, if I hit the transparent button, I should be able to "see through" the
triangles with opacity 0.400000 and the traingles with opacity 1.0000 are still
solid, correct?  If I rotate the object, the 1.00000 opacity triangles should
totally block out the 0.40000 opacity objects, right?

Anyway, this is what I expect to happen and it's not.  A couple other
questions:

Do the vertices in the triangle have to be listed in counterclockwise order for
the transparency to work (some graphics libraries I have used require this)?

Does the lighting effect transparency (how)?

Any assistance you can provide is appreciated.




-- 
William Anderst
Dept. of Kinesiology
Human Performance Lab
Indiana Univerity