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I am using some area lights to illuminate the interior of a cabinet:

enter image description here

However I want to attenuate the lights so their area of influence is much smaller. Like this reference image:

enter image description here

I've tried playing around with the light falloff node but can't get it to do what I want.

Any help at all is greatly appreciated.

Edit 1:

Getting much closer by trying what Rich Sedman linked here. I changed the light attenuation to cubic by dividing the light falloff by the ray length. It's still not where I want it, but progress nonetheless.

cubic

Edit 2:

More progress:

progress

Looking a lot better, but now I'm getting really bright fringing close to the light sources. I am immensely frustrated that it's so difficult to match VRayLight settings in Cycles. I feel like VRay's emission "algorithm" looks much more natural then cycles.

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  • $\begingroup$ What if you use multiple weaker area lights that add up for the final effect? $\endgroup$
    – radoo
    May 12, 2021 at 20:39
  • $\begingroup$ Many thanks, but that won't work. The area lights will still distribute light quadratically and it will end up being a lot more resource intensive to render as well. $\endgroup$
    – fmotion1
    May 12, 2021 at 20:44
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    $\begingroup$ Have you tried this : blender.stackexchange.com/a/101488/29586 $\endgroup$
    – Rich Sedman
    May 12, 2021 at 20:53
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    $\begingroup$ @RichSedman I was able to get cubic falloff working by dividing the light falloff by the ray length as mentioned in your post. Is there a good way to get an even stronger effect? I tried dividing again by the ray length but it's still not where I want to be. $\endgroup$
    – fmotion1
    May 12, 2021 at 21:59
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    $\begingroup$ When we light sets we don’t change physics. Put the light closer, use cutters, etc. $\endgroup$
    – troy_s
    May 13, 2021 at 3:10

3 Answers 3

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Here's a setup to get any falloff power - Constant, Linear, Quadratic, Cubic, etc. and everything inbetween :

result and nodes

Control the overall strength of the light by changing the Strength of the Light Falloff node. Changing the 'Power' changes the falloff with 0 being 'Constant' (ie, irrespective of distance), 1 being Linear falloff, 2 being Quadratic falloff, 3 being Cubic falloff, 4 to falloff to the power of 4, etc. You can adjust the power to any value including, say, 2.5 to be somewhere between Quadratic and Cubic.

EDIT : To get a bit more control over the effect close to the light source you add an extra Maths node to add an offset. This allows you to limit the lower end of the response by making so that it's as if the light is never closer than the specified amount. eg, setting to 0.5 the light will never be in the extreme range.

result and node 2

Another option would be to swap the 'Add' to, say, a Maximum. This way any distance below the set value will be treated as that value (and so not 'blow out') but it will still behave as the required falloff above that threshold.

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  • $\begingroup$ You are a true hero! Thank you so much for that. Going to adjust now. $\endgroup$
    – fmotion1
    May 12, 2021 at 22:28
  • $\begingroup$ Ok, so I think I jumped the gun there. Still getting really extreme blowouts where the light is close to the geometry. This makes sense mathematically. It's just not the look that I'm trying to achieve. Banging my head on the keyboard right now. Thank you though, again, for such a detailed answer. $\endgroup$
    – fmotion1
    May 12, 2021 at 22:37
  • $\begingroup$ Thanks for the edits! Going to try all that now. $\endgroup$
    – fmotion1
    May 12, 2021 at 23:09
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Maybe with this setup you have a little bit more flexibility. And you can "play" around with until you have a result you like. Essentially it is Rich Sedmans setup - just with RGB Curves - which allows changing the curve via mouse.

enter image description here

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I know this is an old post, but maybe this can help anyone googling who has a similar problem. This looks like it might be caused by filmic tonemapper. In Render Properties there is a Color Management panel where View Transform can be toggled from Filmic to Standard, which looks like it might account for the difference you are seeing between Cycles and Vray.

enter image description here

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