Tek nous apporta ses lumieres en ce 2005-10-29 17:07:
> I've got a scene with a large body of water where I want to use some photons 
> for a small area in the foreground. My problem is that I can't hide the 
> transition between the area that has photons and the area that doesnt.
> 
> The problem is: the photons get bent by the refraction and the conventional 
> light obviously doesn't. Which creates a shadow artefact on one side, and a 
> double-lit area on the other.
> 
> Now, I can think of a couple of ways this could be fixed, but they're both 
> impossible in povray!
> Option 1: gradually adjust the refractive index within the photon area, so 
> that it matches the non-photon area at the sides, use this to save photons 
> then switch it off in the main render. But as far as I know pov doesn't let 
> you gradually adjust the refraction. Or does it?
Not possible. You can flaten the relief/normal as you go farther away to acheive a
similar effect.
> Option 2: Adjust the photon spacing so that we have a lot of densly packed 
> photons (using a smaller gather radius) in the foreground area but really 
> low-quality photons in the distance. This will give really nice lighting and 
> be more accurate than what I've got now.
> 
> For the time being, I'll just use photons on a much larger area so the 
> transition's far enough away to not see it. But I'm using literally 10x as 
> many photons as I need for the effect I want.
> 
> Anyway, I'm just posting this here to see if anyone who knows more about 
> pov's photons than me can tell me if either of those options are possible, 
> or if there's any other trick.
> 
> Thanks in advance for any help
Maybe what you need: use photons in the near part and caustics farther away. Maybe
using a 
light_group for the farther part to fill up any ramaining gap.
The part that receive the caustics may be lowered a little to hide a dark band. May
not be possible, 
or very dificult to properly do.
The transition won't be perfect, but the refraction of the vewing rays can make that
hard to 
distinguish. Some judiciously projected shadows can also somewhat hide the transition.
With your option 2, close by area: high quality photons, middle range with low quality
photons, far 
area use caustics.

-- 
Alain
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REMEMBER: WHATEVER HAPPENS, HAPPENS FOR A REASON.

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