Re: Layer anomalies

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Benito Graniela (graniela++at++vsl.ist.ucf.edu)
Thu, 23 Mar 1995 11:43:04 -0500

>
> Performer uses displacepolygon() for fast rendering
>and stencil() for not-so-fast rendering of coplanar geometry.
>Unfortunately, IrisGL's displacepolygon() is inadequate in
>certain situations - you can see poke through when layers
>have large z-slopes and flimmering when they have small z-slopes.
>
> Note that if you specify PFDECAL_BASE_HIGH_QUALITY when
>building your Performer database (See pfLayerMode) you will always get
>accurate coplanar rendering. You need not call stensize() nor stencil().
>
> I am currently working on a fix for the
>displacepolygon() problem that will be available in 2.0
>and will experiment with your database.
>

John Rohlf

You are right PFDECAL_BASE_HIGH_QUALITY will render coplanar polygons
correctly on our database, we have tried that in our lab and it works on
an Onyx and Crimson.The problem is that we need this to work on a Indig^2
Extreme which supports 4 stencil planes. If I understand this correctly it
means that the Indigo^2 Extreme can support up to 16 layers. Well I find
hard to believe that we need more than that in our database so that it can
be rendered correctly.

Here are the stats on one of our machines;

IRIS 4D Graphics Inventory (ginv v1.0)
--------------------------------------
Machine: 4DXG running IRIX version 5.3
1 Screen(s) Accessible on this machine.

Screen Resolution: 1280 x 1024 pixels.
Zbuffer Resolution: 0xFF800000 min 0x7FFFFF max.
Software Accumulation Buffer with 16 bitplanes per colour component.
Alpha bitplanes in DoubleBuffered: 0, SingleBuffered: 0
Red bitplanes in DoubleBuffered: 4, SingleBuffered: 8
Green bitplanes in DoubleBuffered: 4, SingleBuffered: 8
Blue bitplanes in DoubleBuffered: 4, SingleBuffered: 8
Zbuffer bitplanes present: 23
Stencil bitplanes present: 4
Overlay bitplanes present: 4
PopUp bitplanes present: 2
Underlay bitplanes present: 4
User-defined Clipping Planes present: 6
antialiased points available in colormap
antialiased points available in RGB
antialiased lines available in colormap
antialiased lines available in RGB
antialiased polygons not available in RGB
Number of verticies per polygon allowed: 256.

FUNCTIONS AVAILABLE:
afunction, logicop, fogvertex, two-sided lighting, blendfunction, readsource AUT
O/FONT/BACK, readsource ZBUFFER, scrbox, subpixel points, subpixel lines, subpix
el polygons, stereo, texture-mapping, polymode.

FUNCTIONS NOT AVAILABLE:
64x64 patterns.

------

Does anybody see any problems :-)

thanks
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Benito Graniela University of Central Florida
Visual Systems Lab Institute for Simulation & Training
(407) 658-5075 3280 Progress Drive
bgraniela++at++vsl.ist.ucf.edu Orlando, FL 32806-0544
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