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Imagine a light source from which light rays emanate in three-dimensional space. This is what Blender and any other program does in the case of ray tracing.

These light rays hit objects and are partly absorbed and partly reflected by them, and at some point the energy of the ray is so low that its effect can no longer be seen and it finally disappears completely.

In this game, shadows appear where little or no light falls, objects influence each other, and our brain gets a strong spatial impression of an apparent reality.

So far so clear, so far known.

But now imagine in addition an energy source, which functions exactly the same, however with the difference that these rays neutralize the energy of the light sources.

A negative light, so to say.
A light-eater.
A source of darkness.

And I don't just mean an inverted image, but a scene where both forms of energy actually occur simultaneously.

Where the dark source radiates its negative rays, or where it meets the rays of a light source, the energy of the light rays decreases, as if an invisible object absorbs or swallows light.

However, not punctually with an event horizon as with a black hole, but just flowing/smooth, completely according to the inverse-square law which also light follows.

It is difficult for me to explain this, and it is even more difficult for me to represent this with a picture. It is only a theoretical question for the time being, however, with a seriously meant technical interest.

...exactly therefore I ask here also this question to all thinkers, tinkerers and experts.

Above all, I wonder what such a thing could or should even look like.

Is something like this even remotely possible?

Would something like that be somehow feasible with Blender?

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You can assign a negative wattage to a light source - in the .gif below I have 2 lights: one (not moving) at 1000 watts, the other (moving) at -1000 watts. Notice how it also creates a negative "shadow" (whether you want this or not):

LightDark

Here's an image showing the setup (with a nice sphere instead of a cube).

LightDark

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    $\begingroup$ Oh, wow, thanks, very interesting (and amazingly simple) idea! I didn't know that was possible. I will experiment with it... $\endgroup$
    – quellenform
    May 13, 2022 at 0:18
  • $\begingroup$ Wow, I have used negative lights before and never noticed this. I've been attempting some stuff with light paths but I can't get rid of it.. $\endgroup$ May 13, 2022 at 2:22
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    $\begingroup$ See also CGMatter's video on this topic: youtube.com/watch?v=HEzYS8Cx0Zw $\endgroup$ May 13, 2022 at 19:58
  • $\begingroup$ Please correct me if I'm wrong, but is it possible that this only works in combination with "Volume Scatter" in Cycles? I can't really get this to work with Eevee. $\endgroup$
    – quellenform
    May 30, 2022 at 13:03
  • $\begingroup$ The examples above are both done in eevee, I didn't use a volume of any kind. Although, yes, volumetrics in Cycles is far superior to eevee's offerings. $\endgroup$ May 30, 2022 at 13:28

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