Cousin Ricky <ric### [at] yahoocom> wrote:
> Of the 4 unfinished elements that were part of my POV-Ray 30th
> anniversary tribute scene, 3 have been published: DeskLamp, RC3Wood, and
> ShapeOfTheDay.
>
> Unfortunately, there are a couple of lighting problems that showed up in
> the interaction between DeskLamp and ShapeOfTheDay.  Most obviously, the
> caustics are out of control.

I found out what the problem is: photons are broken with true inverse squared
lighting.  (See my post from June 19 in p.beta-test.)  The DeskLamp module
automatically took advantage of true inverse squared attenuation for POV-Ray
3.8, something that my render rig did not do prior to incorporating DeskLamp.

DeskLamp 2.0.1 has true inverse squared attenuation turned off by default; see
p.object-collection.

> The new image applied my light bleeding technique.  It is noticeably
> darker than the 2021 render; I do not yet know why this is.

My best guess is the implementation of the light source.  The hood of the
finished DeskLamp physically occludes the light source, while the earlier place
holder lamp merely simulated the occlusion with a spotlight.  The earlier
spotlight underestimated the extent of the occlusion, so while the direct
illumination is the same for both setups, the global illumination is lower for
the DeskLamp.

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