On Sunday, in article <
[email protected]>
[email protected] "Lee_D" wrote:
> "David G. Bell" <[email protected]> uttered summat worrerz funny
> about:
>
> > Do you know how to get a light-probe image?
>
> Will it make my eyes water? Go on... you now have my full attention 
The idea is that a light probe is a picture of the light falling on a
scene, so that ray-tracing goes from the virtual camera to the object
and then to the light probe. This can replace an array of virtual light
sources, and includes the effects of coloured objects outside the
camera's view.
The hard part is getting the brightness range, since you only have 8-
bits out of most cameras. You can do things by putting a camera on a
tripod and combining under and over-exposed shots.
The trick of a light probe is to have a reflective sphere, or maybe one
that's a light grey. A Christmas Tree bauble, sprayed with grey primer.
And you take a picture of that, getting as large an image as you can.
It also helps to get pictures from opposite directions. Some rays of
light from the other side will just skim the ball, but most of the light
from the far side will be recorded in a very narrow ring.
Really big bearing balls are also good, as long as the chrome's in good
condition.
--
David G. Bell -- SF Fan, Filker, and Punslinger.
"I am Number Two," said Penfold. "You are Number Six."
