[Fieldtrip] Adding lighting to FieldTrip

[David Sankel]

On Thu, Dec 11, 2008 at 4:43 PM, Peter Verswyvelen <bugfact at gmail.com>wrote:

> I'm think 8 is the minimum number of lights hardware must support to be
> OpenGL compiant, but hardware can support more.
> Most games use some kind of "light virtualization technique", were any
> number of lights are allowed but only the closest lights are used for doing
> the shading.
>

Thanks for the input Peter (& Conal).


> I'm not sure if the maximum number of lights applies when using custom GPU
> shaders...
>

I looked into this. An example shader application [1] used normal glLight*
commands to set up the lighting.  This tutorial [2] shows that shaders have
access the light information via. the gl_LightSource array and have the
option to use it or not. I can imagine someone defining unlimited light
parameters with uniform variables in glsl if they really wanted to.

[1] http://cs.anu.edu.au/Student/comp4610/2007/labs/gpu.html
[2] http://www.clockworkcoders.com/oglsl/tutorial5.htm

David

On Thu, Dec 11, 2008 at 10:14 PM, Conal Elliott <conal at conal.net> wrote:
>
>> In TBAG, ActiveVRML/DirectAnimation, and Fran, I embedded lights into
>> geometry, which allows them to be spatially transformed.  Looking in
>> Graphics.FieldTrip.Geometry3, you'll see a comment placeholder for lights.
>>
>> OpenGL is a temporary implementation convenience, so I wouldn't design the
>> API around it.  If more lights get added to a geometry than the current
>> implementation can handle, we can document the limitation and drop some of
>> them at run-time.
>>
>>   - Conal
>>
>> On Thu, Dec 11, 2008 at 12:52 PM, David Sankel <camior at gmail.com> wrote:
>>
>>> Hello All,
>>>
>>> I'm working on adding lighting to the FieldTrip library (ticket
>>> http://trac.haskell.org/FieldTrip/ticket/16). I have some initial data
>>> types here:
>>>
>>> http://hpaste.org/12975
>>>
>>> I'm thinking that the GContext will keep track of which of the 8 opengl
>>> lights are used and enable them if they are.
>>>
>>> I was wondering what ideas folks have had with lighting. Some issues that
>>> are on my mind:
>>>
>>>    - OpenGL limits the number of lights to 8.
>>>    - It would be nice, for a spotlight primitive, to allow the light's
>>>    position and a point it is pointing toward to go through different
>>>    transformations. This would allow a fixed light to follow an object, for
>>>    example. I don't know yet how to provide this functionality.
>>>
>>> Thanks,
>>>
>>> David
>>>
>>> _______________________________________________
>>> FieldTrip mailing list
>>> FieldTrip at haskell.org
>>> http://www.haskell.org/mailman/listinfo/fieldtrip
>>>
>>>
>>
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>>
>
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