cshake nous illumina en ce 2009-02-20 21:08 -->
> I'm trying to figure out what I should use to create diffusion on a spotlight,
> similar to filters used in photography and theater.
> 
> I don't mean the diffusion function in povray itself, but an effect between the
> light source and the target that spreads out the light to create soft edges on
> everything. I already understand how to use the radius and falloff in a
> spotlight source, but all my attempts so far in making a diffusion filter have
> turned out badly.
> 
> I've experimented with using a thin glass-textured plate in the light beam and
> using photon refraction effects, with varying the thickness of the object to
> get more and less diffusion. I found that there seems to be a cutoff
> thickness where it either doesn't change the light at all, or makes the light
> so dull that there is no longer a circular beam even at 4 units away. That
> is with changing the intensity of the light to compensate for fading loss.
> 
> Does anyone have an idea of how to do this?
> 
> 
> 
You can...
- add area_light to your spot_light. This will make the shadows it cast blury.
- using photons and your filter, average a few normals. Keep the normals small.

Sample of the averaged normals:

cylinder{z, z+0.01, Radius pigment{rgbt 1}
	#local Smpl = 5; #local R = seed(0);
	normal{average normal_map{
		#while(Smpl >0)
		[1 bumps 0.1 scale 0.01 translate<rand(R),rand(R),rand(R)>*0.01]
		#local Smpl = Smpl -1;
		#end
			}
		}
	interior{ior 1.5}
	photons{target refraction on}
	}

The value of "Smpl" controlls the smoothness of the bluring. Don't use a large 
value, as it affect the rays on two surfaces, and squares the number of samples.
The value after bumps controlls the bluring's intensity.


-- 
Alain
-------------------------------------------------
You know you've been raytracing too long when your personal correspondence to 
friends starts out with #Dear Linda =
Ken Tyler

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