OK, here's an idea, if someone feels up to programming it.  How about
have a finite speed of light for use in animations?  The clock variable
would define "time" in the scene, and light would travel outwards at a
given speed from all the lights in the scene, illuminating things only
when the light had reached them and had enough time to travel back to
the camera.  Presumably, one would have to keep track of the distance a
particular ray would have "travelled", and check if it has had long
enough to reach the camera.

This could be used to very interesting effect in animations with a slow
speed of light.  A room illuminated by a few lights would gradually
light up, but then any mirrors in the room would begin to light up
later.  Also, moving objects would appear at different places in
mirrors.

I guess this wouldn't work too well with radiosity, though.

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Andrew wrote:
> 
> OK, here's an idea, if someone feels up to programming it.  How about
> have a finite speed of light for use in animations?  The clock variable
> would define "time" in the scene, and light would travel outwards at a
> given speed from all the lights in the scene, illuminating things only
> when the light had reached them and had enough time to travel back to
> the camera.  Presumably, one would have to keep track of the distance a
> particular ray would have "travelled", and check if it has had long
> enough to reach the camera.
> 
> This could be used to very interesting effect in animations with a slow
> speed of light.  A room illuminated by a few lights would gradually
> light up, but then any mirrors in the room would begin to light up
> later.  Also, moving objects would appear at different places in
> mirrors.

You can do that with having fade_distance rely on the clock setting.

-- 
***** This was posted with the express permission of *****
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** HIS HIGHNESS ADAM H KERMAN LORD AND MASTER OF USENET **
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*********** We are simple servants of his will ***********

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from Ken's links:

http://www.anu.edu.au/physics/Searle/Obsolete/Raytracer.html

You can probably find a couple of others with a web search.

	~Kevin Wampler~

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Having too much Pratchett lately? :))


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg

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There's no reliable accurate method to do this in POV (at present)  I don't
think fade distance would give the results desired in this case, light less
than the fade distance would get significantly brighter and you'd lose your
falloff properties.

A quick, easy way to get simple, usable results would be to add a hollow
sphere with no_image and no_reflection (assuming megapov or 3.5) and change
the radius with the clock variable.  This would simulate light emanating
from a point light in a sperical shape (The sphere will not be visible at
all, but it will still cast a shadow, essentially blocking the light beyond
it's surface) Multiple lights would be a little more difficult.  Of course
this method has pitfalls regarding reflection and refraction.

-tgq


--
camera{location z*13look_at 0}light_source{15 15looks_like{sphere{0 10
}pigment{rgb 1}finish{ambient 15}}}union{torus{3,0.5rotate x*90}cone{y
*4,.5,-y*8,0}cone{-x*4,.5,x*8,0}pigment{rgb<.7,.6,.4>}finish{ambient 0
diffuse 0reflection{1fresnel on metallic 1}}interior{ior 25}rotate 15}
plane{y,-7pigment{checker rgb 0rgb 1scale 4}finish{diffuse.1}}//   TGQ

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Andrew wrote:

> OK, here's an idea, if someone feels up to programming it.  How about
> have a finite speed of light for use in animations?

Have you checked out Backlight, the relativistic raytracer?

http://www.anu.edu.au/Physics/Searle/Downloads.html
--
Jon A. Cruz

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