Hi Ken,

The depth sorting is done on distance from the center of the
drawable's bounding box to the eye point.  Its done purely at the
drawable level, so if indivual polygons overlap then you'll find
problems with rendering order.  This isn't an OSG specific issue, but
a general real-time graphics issue associated with use of z buffers.

For things like sphere's you can force the polygon ordering to be a
bit more ideal by drawing all the transparent back faces in one bin
i.e. 10, then draw all the front faces in the next bin i.e. 11.

Robert.

On 5/24/06, Ken Sewell <[EMAIL PROTECTED]> wrote:

How exactly does OSG do transparency sorting?  I have an application in
which there are several locations that have concentric spheres.  Each
sphere has a color with an alpha of ~0.3, has BLEND and TRANSPARENT_BIN
set in its stateset. I am encountering two issues:

 - I always see the outer spheres, but the inner spheres 'pop' in and out
as the camera moves through the scene.  They're there for a few seconds,
change camera angle and they disappear, change again and they are back.

 - When two spheres overlap, sometimes I only see one sphere and it seems
to be clipping the other, instead of rendering the overlapping part
of both.

 - I am creating my own geode/drawable (which I haven't done much) is a
bounding box/sphere automatically created or do I need to manually add
one?

  Any ideas about what I might be doing wrong?


Ken Sewell
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