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I set out to recreate Rembrandt lighting in Blender using 2 area lights and a Suzzane. I couldn't 'isolate' away one side of the face from the light so I kept reducing the area light's sizes all to no avail. Made no difference. At 0m, nothing was visible (no idea why this is the case, a point light has a size of 0m and displays just fine?), anything past that and it looked the same. Or so I thought

I decided to set it a value marginally above 0 when I get this effect out of nowhere:

enter image description here Note, no special material was used here. Just your regular default material at play here along with an area light

The file's attached here: link

What exactly is causing this Moire effect internally within Blender? It is a very intriguing effect and I'd love to know how it works so as to exploit it in future renders. Also curious as to why my area light just shuts off at a size value of 0. Point lights have a size of 0 and visibly light up things, do they not?

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  • $\begingroup$ A Point Light is really a point (dot) in the mathematical sense, so it doesn't have a size : it only have a position (nor rotation by the way). I will dig into the moiré effect. $\endgroup$
    – thibsert
    Commented Jan 1 at 4:24
  • $\begingroup$ When I render 0.02 I get a correct render. Are you using the latest blender version? It seems also logical, that an area light with the area of 0 would not emit light. $\endgroup$
    – Leander
    Commented Jan 7 at 18:25
  • $\begingroup$ @Leander I am on Blender 3.6.4, not particularly old, so I am not sure why it is occurring in this. Also, wouldn't an area light with an area/size of 0 be identical to a point light? $\endgroup$
    – Hash
    Commented Jan 7 at 19:38
  • $\begingroup$ Try blender 4, please. $\endgroup$
    – Leander
    Commented Jan 7 at 23:12
  • $\begingroup$ @Leander I would still like to know why the issue occurs under the hood. 3.6.4 is a stable release so it couldn't have been due to a bug $\endgroup$
    – Hash
    Commented Jan 8 at 8:41

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Not really an answer, but maybe some clues.

A Point Light is really a point (dot) in the mathematical sense, so it doesn't have a size : it only have a position (nor rotation by the way). It works like an ideal lightbulb.

On the contrary, an Area Light is meant to have a surface. So it have a size, and also a rotation. It works like a screen or any emissive plane.

Also, an Area is designed to work with some reasonable values. If you use an Area and give it an absurd low size, the lighting model just doesn't work (that light should be approximated by a Point) ; which give us, apparently, that interesting Moiré effect.

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  • $\begingroup$ That much I have understood too. I would like to know exactly why the Moire effect occurs in this particular situation $\endgroup$
    – Hash
    Commented Jan 2 at 2:17

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