"Greg M. Johnson" wrote:
> 
> Thanks for the effort.  What I eventually am trying to get is a "christmas bulb in
> a wiffle ball in the fog," except my wiffle ball is an isosurface.
> 
> This whole effect renders quickly, is intuitively set up, and only requires a
> White*14 intensity SPOTLIGHT.
> 
> When i go to POINTLIGHT, I have to put that plane in there and raise the intensity
> several orders of magnitude to get it to work. And as you said, requires a long
> render time.
> 
> What's the difference between spot & point lights???  Is this "intentional"??
> 
	The difference is explained in the help with the "ratio" keyword. In
short, when you use a spotlight, PoV will divide the media into "lit"
and "unlit" areas and take more samples in the lit areas (with the
default settings, it will take almost no samples in the unlit area).
With the pointlight there is no "unlit" area and POV takes samples along
the whole ray. When you have an atmospheric media it means that a lot of
samples will be very far away and won't appear... Adding the plane cuts
the media in two (and therefore doubles the render time) wich forces
enough samples to be taken in front of the plane to make the media
appear (I've used a similar trick in my last irtc entry to make the mast
lamp visible: http://www.enst.fr/~jberger/images/jbhome.jpg )

		Jerome

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* they'll tell you what can't * mailto:ber### [at] inamecom
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