Radiosity is awesome, but it can be very slow, especially at the quality
levels needed to deal with small, bright objects.  Sometimes, though,
you can use tricks to fake radiosity.

I've already mentioned using a spotlight to replace would-be radiosity
from the hood interior, but what about radiosity *to* the hood interior?

In the attached montage, the top row has an external light shining into
the lamp hood; the middle row is in mostly shade; and the bottom row is
lighted.  The leftmost column uses radiosity with recursion_limit 2, a
typical setting.  The second column uses 4, a higher setting than is
normally used, but which illuminates deeply shadowed areas and brings
out their details.  The third column has no radiosity, and uses a flat
ambient throughout the scene, varying the ambient only in proportion to
the diffuse in a given texture.  The rightmost column also uses no
radiosity, but uses gradient textures with varying ambient levels to
simulate ambient occlusion.  The ambient levels are all set by the lamp
macro.  Of course, any ambient setting is necessarily a compromise, but
I think I've achieved a good balance.

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Attachments:
Download 'test_hood_interior-pbi.jpg' (191 KB)

Preview of image 'test_hood_interior-pbi.jpg'

Cousin Ricky <ric### [at] yahoocom> wrote:
> Radiosity is awesome, but it can be very slow, especially at the quality
> levels needed to deal with small, bright objects.  Sometimes, though,
> you can use tricks to fake radiosity.
>
> I've already mentioned using a spotlight to replace would-be radiosity
> from the hood interior, but what about radiosity *to* the hood interior?
>
> In the attached montage, the top row has an external light shining into
> the lamp hood; the middle row is in mostly shade; and the bottom row is
> lighted.  The leftmost column uses radiosity with recursion_limit 2, a
> typical setting.  The second column uses 4, a higher setting than is
> normally used, but which illuminates deeply shadowed areas and brings
> out their details.  The third column has no radiosity, and uses a flat
> ambient throughout the scene, varying the ambient only in proportion to
> the diffuse in a given texture.  The rightmost column also uses no
> radiosity, but uses gradient textures with varying ambient levels to
> simulate ambient occlusion.  The ambient levels are all set by the lamp
> macro.  Of course, any ambient setting is necessarily a compromise, but
> I think I've achieved a good balance.

Wow, your rendered image looks nice, and I just understand what is "ambient
occlusion" last week...(because I was looking into the various type of UV-map)

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Cousin Ricky <ric### [at] yahoocom> wrote:
> Radiosity is awesome, but it can be very slow, especially at the quality
> levels needed to deal with small, bright objects.  Sometimes, though,
> you can use tricks to fake radiosity.

> I've already mentioned using a spotlight to replace would-be radiosity
> from the hood interior, but what about radiosity *to* the hood interior?

> In the attached montage,
.....
The ambient levels are all set by the lamp
> macro.  Of course, any ambient setting is necessarily a compromise, but
> I think I've achieved a good balance.

Wow.  You truly are able to maintain meticulous focus, and apply your knowledge
and creativity to addressing these kinds of issues.

If not actually photographic, every one of these images is textbook-quality.
That lamp looks _real_.

I'm sure that all the work you've done on this so far could fill an entire
chapter in a computer graphics textbook.   Certainly an extensive blog post or a
monograph on faking ambient occlusion with POV-Ray...   ;)


Great work as always, Richard.

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I would have thought the 4th column was using radiosity if I hadn't read the
description so yes I would say it worked.

I guess for a more complex image with lots of objects this method would take a
lot of effort (probably too much) but it is a good experiment.

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