> Alain<aze### [at] qwertyorg>  wrote:

>>> I'm trying to set up a model for a physics experiment I'm doing. The gist of it
>>> is there is a crystal suspended in a liquid over a light source with a camera
>>> above it. I'm trying to set up a povray model where the liquid and the crystal
>>> have different indexes of refraction. The problem is it seems that changing the
>>> index of refraction of the crystal has no effect on the model. IE, if the index
>>> of refraction of both the crystal and the liquid are one, the crystal is still
>>> visible. Any help doing this would be appreciated.
>>>
>>> I've pasted my code below. The liquid is the ellipsoid and the crystal is the
>>> box.
>>>
>>
>> A few questions:
>> Why are your dimentions so small?
>> The camera is at 0.01 unit, the sphere have a 0.001 unit radius, the box
>> is only 2/10000 unit whide.
>>
>> You seems to be working in meters, there is nothing preventing you from
>> working in mm or smaller units.
>
> I'm probably missing some kind of functionality in Pov-ray but I'm doing it in
> order to keep the ellipsoid from refracting the fall off in lighting from the
> area_light. Keeping it small and close to the light gives the minimum amount of
> distortion. Is there another way to make a light source that illuminates a wider
> area? Ideally I'd like an infinitely large (or at least very large in comparison
> the the objects) plane of white light below the crystal. In the actual
> experiment, the crystal will be many orders of magnitude smaller then the light
> source.
> Thanks again for everyone's help
>
>
In your case, the actual light_source is probably not needed. You can 
only keep the background plane, or even only use a white background.
Just tested. A white plane and no light looks the same as the light with 
a looks_like plane.

Given that a plane is infinite, you only need to work in an unit system 
that is convenient and place the back plane and the camera as you need them.

You can also use a large box or a whide cylinder. If they are 1000 times 
larger, or more, than the cristal they will act exactly lyke a plane.



Alain

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