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> Date: Sat, 26 Jun 1999 21:39:09 -0700
> From: Eric Hawthorne <[EMAIL PROTECTED]>
> Subject: [JAVA3D] Strange black holes in rendered object
> To: [EMAIL PROTECTED]
>
> This is Java3D 1.1.1 OpenGL on a graphics card called S3 ViRGE
Youch! That's an old card!
> I'm rendering (without lighting or appearance attributes, just geometry color)
> a triangle strip array that is basically an undulating surface.
> I am always seeing many rectangular holes in the rendered object, which
> are not there in the triangle strip array model. Altogether, about 1/10 of the
> surface is holes. I say holes because one can see through them to the next
> undulation of the surface. The holes are kind of randomly and fairly evenly
> distributed across the surface, but there appears to be a linearity to their
> arrangement
> as though the holes are occurring here and there along each strip..
> The rest of the surface is rendered in its geometry-specified color.
> Very weird.
> Anyone seen anything like this?
> The rest of the surface is rendered in its geometry-specified color.
>
It sounds like you might have a polygon winding problem. In 3D, the order
points are specified in a polygon determines if the polygon is front facing
(the polygon's front is toward the viewer) or backfacing. My guess is you
have polygons wound in such a manner that some are front facing and some
are back facing.
By default, Java 3D does not display back facing polygons (they are culled
from the scene). A quick test to determine if this is what you are
seeing is to change the PolygonAttributes structure for your Shape3D object
holding your triangle strip array:
polygonAttributes.setCullFace(PolygonAttributes.CULL_NONE);
Hopefully that will fix things,
Dan Petersen
Java 3D Team
Sun Microsystems
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