| Re: Realistic Illumination, IDL & OpenGL [message #37821] |
Sat, 31 January 2004 00:40  |
nasalmon
Messages: 33
Registered: August 2003
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"Rick Towler" <rtowler@u.washington.edu> wrote in message news:<bvetav$jfc$1@nntp6.u.washington.edu>...
> "Neil" wrote in message...
>
>
>> For Object Graphics to emulate reality, illumination mustbe
>> accurately represented. Take for example an outdoor scene, where sky
>> background emission above and up-welling emission below bathes an
>> object in different intensities from all directions. Can this be
>> accurately described in IDL or OpenGL?
>
> It depends what you mean by accurately described. Lighting in openGL is
> more of an art than a science. Simply throwing in a few lights rarely leads
> to an acceptable rendition of a scene. Proper texturing and camera
> placement are key. If there is motion in the scene (either camera or actor)
> causing the lighting to change you can generate procedural textures. Take a
> look at a few ~2-3 year old 3d games to get an idea of what you can do with
> good texturing.
The difficulty i have is that i am trying to use Object Graphics as a
science to speed my scene simulation, which i have already coded up in
Direct Graphics with good scientific precision. Somehow i need to be
quantitatively creative in Object Graphics to create the same result
as in Direct Graphics. Strategically for the further development of
Object Graphics, if note is taken of the science of reflections /
illumination a more accurate description of rendering will result.
However, i can seen this is not a priority of the gaming industry, but
IDL with is scientific background would be interested in enabling a
more scientifically precise Object Graphics, as opposted to art based
Object Graphics for computer gaming.
>
> If you need to go further (or do it faster) you'll need to move beyond IDL.
I may want to go further and faster, if so what would you recommend?
I suppose what i really want to do is to go faster with scientifically
precise graphics.
>
>> In IDL Object Graphics there is the possibility to bring in the
>> "light" by way of obj_new "IDLgrLight". However, this can only be:
>> type 0) Ambient; 1) point source; 2) collimated beam; 3) spot light
>> (apertured). The number of lights is limited to 8. Is this
>> illumination limited by IDL or the OpenGL on which IDL operates?
>
> All openGL implementations support at least 8 lights, some support more.
> I don't know if there is a hard limit in IDL but my guess is that this limit
> is imposed so IDL will behave the same way regardless of the underlying gl
> implementation.
>
> 8 may seem like a small number but I think you'll find that it doesn't take
> a lot of lights to render an acceptable scene as long as you are creative
> with placement and textures.
>
>> Gereral illumination in an outdoor environment has something of an
>> angular distribution, for an overcast day at least. This might be
>> represented in an alt-azimuth coordinate system; large amount of
>> emission at zenith, with some kind of distribution coming down to the
>> horizon, with some up-welling illumination from the ground. This could
>> be either simulated by a very large number of point sources or ambient
>> illumination with some angular distribution on it. Are there plans to
>> introduce this kind of "light" into IDL in future versions?
>
> If I understand you, this can be done in IDL right now. You just have to be
> creative. :)
>
> Or you might want to consider pov-ray.
Pov-ray? What on earth is that?
>
> -Rick
many thanks for your help
Neil
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