From: Lawrence Bertoldi (lberto++at++sgi.com)
Date: 07/11/2000 07:46:38
The only problem with glPolygonOffset is that you will get one color or the other!
If your ok with that then fine but If you are looking for a Blending of the two
lines
you will need to set up blending! I would do this in a predraw callback with OpenGL
calls! So you might want to look at glBlendFunc and glBlendEquationEXT!
Benedikt Kessler wrote:
> Hi!
>
> Antialiased lines will probably not fix the problem; the Octane has no
> multisampling capabilities and therefor you need alphablending to draw
> your antialiased lines. You may get the colors of the lines mixed when
> using antialiased lines (do you want this to happen?). But as your lines
> are partly be overlapping, I think you may get similar problems as
> before (due to different depth values of the overlapped lines when they
> do not start and end at the same coordinates).
>
> Take a look at the glPolygonOffset manpage. A small offset to your lines
> (different offsets for different colors) may help the lines from mixing
> up.
>
> Bye! Benedikt
>
> Brian Furtaw wrote:
> >
> > You are seeing the the results of rendering on a machine with
> > anti-aliasing (the IR) and rendering on a machine without(the Octane).
> > The Octane does have the ability to render anti-aliased lines. I can't
> > find any direct support for line smooth in Performer although some one
> > else might. To enable this feature in OpenGL use
> > glEnable(GL_LINE_SMOOTH), read the glLineWidth man page for details
> > about anti-aliased lines on the Octane. You could enable and disable
> > line smooth in a pre and post draw callback. You can use glGetString
> > GL_RENDERER to identify when you are running on the Octane and install
> > callback.
> >
> > I don't know if you have enabled blending or not. As an experiment set
> > the pfTransparency() to PFTR_HIGH_QUALITY this may enable the linesmooth
> > on the Octane. This will also slow things down so use it only when you
> > need it.
> >
> > Brian
> >
> > christopher.g.dorosky++at++lmco.com wrote:
> > >
> > > Hello,
> > >
> > > I have an application that draws thin lines (about 5 pixels wide or so),
> > > around areas of interest. These lines can be different colors. In one
> > > instance, there can be yellow and red lines which overlap in places. The
> > > problem is, I am seeing different results on different machines.
> > >
> > > On an Onyx2 IR2: Overlapping yellow and red lines blend to create an orange
> > > segment in the overlap region.
> > > On an Octane: Overlapping yellow and red lines flash back and forth
> > > depending on how I look at them. Sometimes, they even stripe between yellow
> > > and red.
> > >
> > > The octane effect is annoying. Does anybody know how I can either assert
> > > one color as dominant, or allow them to blend like the Onyx2 does? The lines
> > > are created with pfGeosets.
> > >
> > > Thanks!
>
> --
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-- See Ya,Lawrence Eugene Bertoldi Technical Consultant vnet 238-8949 Silicon Graphics phone 301-572-8949 Silver Spring MD. email lberto++at++clubfed.sgi.com
~;-}>
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