Hello, I’ve been looking for a way to have one particular object not be affected by one light. I have other lights in the scene that I wish to still have affect the object. In object properties ive seen an option for ‘Light groups’ but im not sure if that has anything to do with that.
As it is said in the article, light groups are light mixing.
Lights illuminations are individualized.
The ability, for an object, to be excluded from illumination and shadows from lights is a light linking. That does not exist in Blender.
In Blender, if you want such property defined from objects, you have to put objects in different collection, enable/disable different set of collections in different View Layers and mix those View Layers in compositor.
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Just a thought.
Things have object ID’s right? So each light probably has a unique individual ID too. I’ll call that a Light ID, LID.
There is a shader node with info. about what type a light ray is. Properties like is-camera-ray are there.
If the LID is available in shader nodes then and object could have nodes that essentially say “if LID = x then this object is invisible”. Or it has no shadows or diffuse etc.
Some node expert could investigate that.
The people behind the GooEngine build of Blender have done exactly this- they’ve implemented object and shader light grouping and light linking (only for Eevee)
But is there a Light ID and is it available to shaders now in regular Blender?
It may not be the full power of light linking but people could use the LID now for some things.
P.S. I guess a script could get the LID. Maybe make it available in nodes.
Not in regular Blender, sadly, but in the custom build. It might be possible in regular Blender with a script, I haven’t tried it
There is a custom build of blender that has light linking features. Its a paid build available on bmarket.
There’s several custom builds with light linking, cool 
GooEngine is free, which makes it better for me, but it’s always nice when there’s multiple options
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Thats wonderful then free is great! I Will try it.It supports eevee.