On 2024-02-11 11:29 (-4), Alain Martel wrote:
> 
> In povray_30th_anniversary.20230605.jpg, my guess would be not enough
> photons being shot. If you use a count, I suggest switching to spacing.
> When using count, remember that it's spread across all light_source and
> all target objects. ALL non-shadowless light will emit photons unless
> they have this photons block :
> photon{refraction off reflection off}
> as the default is :
> photon{refraction on reflection on}

I stopped using photons count many years ago, probably in 2006, when I
bought a computer with a decent amount of memory.  Both images used
photons spacing, and they used the same spacing value.

> You may use a non unit value for the target attribute of an object. That
> will be used as a spacing multiplier.
> target 0.2 will DIVIDE the spacing by 5 (meaning 25 times more photons),
> while target 2 will double the spacing (meaning 4 times less photons),
> used when shooting photons at that object.

That is just side-stepping the issue, because the '30' object uses the
identical photons block in both images.  All that changed was the light
source.

> Maybe also increase the jittering of the photons. It looks like there is
> none.

Jitter is turned on permanently, and as recommended in the POV-Ray
reference, I have not changed the default value.  (I neglected to
mention this in the DeskLamp user manual.)  Are you attributing the
discrete rainbow stripes to non-jittering?  That is most likely due to
imperfect anti-aliasing (interpolate 2) in the image map used to define
the glass '30'.

To be clear, the changes between these images, including the one I
posted in in 2021, were in the include files, not in the scene
definition itself.  The bottom line is that there is something about the
lamp fixture that causes the caustics to go haywire.

> The dark area in the reflection of the desk lamp look credible. I often
> see something similar IRL. You may try to give the interior of the shade
> an finish that include a moderate amount of emission. That should make
> the darker area less obvious.

An emitting object cannot be darker than the surface it is
illuminating--in this case, the interior of the lamp hood.  The problem
is that the emission on the light bulb object is too low.  I will not
put an emission on the lamp hood interior, because it does not emit
anything.

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