----- Original Message -----
From: Matthew Warren <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: November 4, 1999 9:12 AM
Subject: Re: [JAVA3D] Strange waves in my cubes
> I have seen a similar effect when displaying rows of sphere primitives
that
> overlap, I wasnt sure why and didnt consider it a problem - I assumed it
was
> to do with the number of triangles making the spheres. IE: triangles that
> partially covered each other when spheres overlapped where removed rather
> than clipped to the right shape?
>
> I assume from reading below this is the culling problem?
>
I don't believe that is correct. J3D uses OpenGL for the rendering and
OpenGL doesn't remove primitives when they overlap. It just draws them.
> Is it possible to get J3D to clip intersecting tringles when shape3D's
> intersect so they render with 'flush' edges rather than just removing the
> triangle?
>
> Matthew.
>
The culling I am referring to is J3D's default behaviour of removing
primitives whose normals point away from the viewer. This normally means
the primitives are "hidden" from view in the case of a sold object. When an
object isn't tesselated into enough triangles, there is a possibility that
normal smoothing will cause at least one vertex of an edge triangle to have
a normal that points away from the viewer. In this case, the whole polygon
would be culled leaving holes in the object. I believe that is what we are
see in Patrick's image.
To test my theory, Patrick could turn culling off and see if the problem
goes away. If that is the case, my next course of action would be to better
tesselate the rounded edges of the cube and then re-activate culling since
it provides better performance.
>
> >This appears to be a culling problem. The only triangles that are
> >disappearing are those at the edges of your rounded cubes. My best guess
> >is
> >that the rounded edges of the cubes are not tesselated enough i.e. not
> >enough triangles were used to define the rounded sections. Because there
> >aren't enough triangles, some of the triangles have normals that are not
> >quite correct and they are being culled. As you rotate the view,
naturally
> >different triangles would be affected. To fix the problem, you need to
> >create the cubes with more triangles in the rounded regions. Hopefully,
> >your code can be adjusted to do that.
> >
> >Roberto Speranza
> >President, Dot Internet Solutions Inc.
> >mailto:[EMAIL PROTECTED]
> >http://www.dotinc.net/
> >----- Original Message -----
> >From: Patrick van Bergen <[EMAIL PROTECTED]>
> >To: <[EMAIL PROTECTED]>
> >Sent: November 4, 1999 7:21 AM
> >Subject: [JAVA3D] Strange waves in my cubes
> >
> >
> > > Hai there,
> > >
> > > I am building an application that contains a number of rounded cubes.
> >When
> > > these cubes overlap eachother I get these strange 'waving' effects,
that
> >can
> > > best be explained by looking at the attached picture. I say waving
> >because
> > > triangular waves go through the sides of the cube when I zoom in and
out
> >of
> > > the objects.
> > >
> > > I tried changing some of the renderingattributes of the appearance
> >without
> > > much effect.
> > >
> > > Has anyone seen such an effect before? I am not doing anything special
> >here.
> > >
> >
>
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>
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===========================================================================
> To unsubscribe, send email to [EMAIL PROTECTED] and include in the
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> [EMAIL PROTECTED] and include in the body of the message "help".
Roberto Speranza
President, Dot Internet Solutions Inc.
mailto:[EMAIL PROTECTED]
http://www.dotinc.net/
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To unsubscribe, send email to [EMAIL PROTECTED] and include in the body
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