Re: [info-performer] bounding sphere with non-uniform scaling

Date view Thread view Subject view Author view

From: Allan Schaffer (allan++at++sgi.com)
Date: 07/29/2004 18:03:19

Hi John,

I think you're correct. I tried a few scaled variants of esprit.pfb --

esprit.pfb Radius = 3.133899
esprit.pfb.1,1,0.01.scale Radius = 3.133899
esprit.pfb.1,1,0.01.scale.1,1,100.scale Radius = 313.389893

The first case the model looked normal (of course). In the second the model
was very very flat as expected. In the third case the model looked correct
but the bounding sphere was 100x normal size.

Doesn't make sense to me, looks like a bug. This will be.. SCR 918816.

Allan

John Kelso wrote:
> Hi all,
>
> I have a file that's the output of a simulation, containing about 2500
> points. The x and y don't have much of a range as they go across z. We
> wanted to use the scale pseudo-loader to make the data display something
> we could actually see.
>
> If I run my little bounding program:
>
>
>>dpf-bounds test.pfb 2>/dev/null
>
> bounding sphere radius = 78.796997
> (Performer's pfNode->getSphere returns radius = 78.796997)
> X: 0.000000 - 0.000100, delta: 0.000100 center: 0.000050
> Y: 0.000200 - 0.014889, delta: 0.014689 center: 0.007544
> Z: -35.424000 - 122.169998, delta: 157.593998 center: 43.372999
>
> the bounding sphere I calculate is based on a sphere around the data's
> bounding box. The one reported by Performer is on the next line in
> parentheses.
>
> If I scale it mostly in X I get this:
>
>>dpf-bounds test.pfb.1000000,100,1.scale 2>/dev/null
>
> bounding sphere radius = 93.297958
> (Performer's pfNode->getSphere returns radius = 78797000.000000)
> X: 0.100000 - 100.000000, delta: 99.900000 center: 50.050000
> Y: 0.020000 - 1.488900, delta: 1.468900 center: 0.754450
> Z: -35.424000 - 122.169998, delta: 157.593998 center: 43.372999
>
> It looks like the radius returned by Performer uses just the X scale
> value. The data ranges look OK.
>
> If I switch the X and Z scales:
>
>>dpf-bounds test.pfb.1,100,1000000.scale 2>/dev/null
>
> bounding sphere radius = 78797000.000000
> (Performer's pfNode->getSphere returns radius = 78797000.000000)
> X: 0.000000 - 0.000100, delta: 0.000100 center: 0.000050
> Y: 0.020000 - 1.488900, delta: 1.468900 center: 0.754450
> Z: -35424000.000000 - 122170000.000000, delta: 157594000.000000 center:
> 43373000.000000
>
> Performer returns the same radius, but it's correct.
>
> Is this correct behavior for the Performer bounding sphere? Am I just
> using it wrong? How does this affect culling and other activities that
> use the bounding sphere? Does perfly use it to size and center the
> object?
>
> I can send the data as a pfb if it'll help.
>
> Thanks,
>
> -John
>
>
> -----------------------------------------------------------------------
> List Archives, Info, FAQ: http://www.sgi.com/software/performer/
> Open Development Project: http://oss.sgi.com/projects/performer/
> Submissions: info-performer++at++sgi.com
> Admin. requests: info-performer-request++at++sgi.com
> -----------------------------------------------------------------------
> SIGGRAPH 2004 Friends of Performer BOF:
> Tuesday, August 10, 6pm - 8pm Wilshire Grand Hotel, Sierra Ballroom
> ----------------------------------------------------------------------- 

-- 
Allan Schaffer                                            allan++at++sgi.com
Engr. Dept. Manager, Visual Systems Group                1-650-933-2160
Silicon Graphics                                     http://www.sgi.com

Date view Thread view Subject view Author view

This archive was generated by hypermail 2b29 : Thu Jul 29 2004 - 18:03:39 PDT