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I asked this in p.general in a thread, but no-one has answered, so I'll ask
it here in its own thread:
What do vista and light buffers do and how they work? A precise answer from
someone who knows well the algorithm, please.
I'm very interested in knowing this.
--
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):_;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/
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On 30 Aug 2000 10:30:51 -0400, Warp wrote:
> I asked this in p.general in a thread, but no-one has answered, so I'll ask
>it here in its own thread:
>
> What do vista and light buffers do and how they work? A precise answer from
>someone who knows well the algorithm, please.
> I'm very interested in knowing this.
Not a precise answer, but...
The vista buffer is a 2-d representation of the locations of the objects in
the scene, as seen from the camera. When tracing camera rays, you need only
check the objects at that location in the vista buffer.
The light buffers are similar, one per light, and are used for tracing
shadow rays.
--
Ron Parker http://www2.fwi.com/~parkerr/traces.html
My opinions. Mine. Not anyone else's.
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> The light buffers are similar, one per light, and are used for tracing
> shadow rays.
Don't know well the algo though...
For lights these are not only 2D but 3D: a box which
faces have a 2D representation of the objects around. Using light
buffers can be greatly memory expensive if a lot of lights are used
(as in my unique IRTC entry 2 years ago:
http://oz.irtc.org/ftp/pub/stills/1998-08-31/afterain.jpg
) but should speed up almost all scenes. However sometimes light
buffers are not desirable for instance when some objects are not
well projected on the light boxes (it happened me once, but don't
remember exactly how).
*** Nicolas Calimet
*** http://pov4grasp.free.fr
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On Wed, 30 Aug 2000 19:34:39 +0200, Nicolas Calimet wrote:
>> The light buffers are similar, one per light, and are used for tracing
>> shadow rays.
>
> Don't know well the algo though...
> For lights these are not only 2D but 3D: a box which
>faces have a 2D representation of the objects around. Using light
That's still 2D.
--
Ron Parker http://www2.fwi.com/~parkerr/traces.html
My opinions. Mine. Not anyone else's.
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Ron Parker <ron### [at] povray org> wrote:
: The vista buffer is a 2-d representation of the locations of the objects in
: the scene, as seen from the camera.
How does povray determine those 2D areas?
--
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):_;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/
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On 30 Aug 2000 18:40:54 -0400, Warp wrote:
>Ron Parker <ron### [at] povrayorg> wrote:
>: The vista buffer is a 2-d representation of the locations of the objects in
>: the scene, as seen from the camera.
>
> How does povray determine those 2D areas?
By projecting the bounding boxes onto a sphere, I suspect. I've never looked.
--
Ron Parker http://www2.fwi.com/~parkerr/traces.html
My opinions. Mine. Not anyone else's.
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On 30 Aug 2000 23:55:38 -0400, ron### [at] povrayorg (Ron Parker)
wrote:
>>: The vista buffer is a 2-d representation of the locations of the objects in
>>: the scene, as seen from the camera.
>>
>> How does povray determine those 2D areas?
>
>By projecting the bounding boxes onto a sphere, I suspect. I've never looked.
That's one way to put it but maybe it only stores the bounding box
vertices in spherical coordinates with respect to every light source?
That would be faster and less memory consuming, I think.
Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] usanet
TAG e-mail : pet### [at] tagpovrayorg
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Ron Parker <ron### [at] povrayorg> wrote:
: The light buffers are similar, one per light, and are used for tracing
: shadow rays.
What about area lights?
--
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):_;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/
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> : The light buffers are similar, one per light, and are used for tracing
> : shadow rays.
>
> What about area lights?
From the POV docs:
"The light buffer is created by enclosing each light source in an
imaginary box and projecting the bounding box hierarchy onto each of its
six sides. Since this relies on a fixed light source, light buffers will
not be used for area lights."
*** Nicolas Calimet
*** http://pov4grasp.free.fr
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Nicolas Calimet wrote:
> From the POV docs:
> "The light buffer is created by enclosing each light source in an
> imaginary box and projecting the bounding box hierarchy onto each of its
> six sides. Since this relies on a fixed light source, light buffers will
> not be used for area lights."
Hey Warp, RTFM !
TeeHee
--
Ken Tyler - 1400+ POV-Ray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/
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