Since there is an experimental build on this. I think we should have a thread here discussing it, offering solutions, bugs maybe.
Thanks to the devs for working on this.
In my short time of tinkering with it, I have noticed light linking seems to have an issue with glass material. If you place something behind a glass and decided to exclude that object from a light that affects the glass. The object does not get excluded from that light.
I am wondering if this is something the devs are aware of.
I placed a timestamp on the vid. Seems in the latest experimental build. Light bounces from a light will affect objects that it is not linked to, it will not directly light those assets that are excluded but the light bounces will affect them.
Maybe a option can be added to turn this off and on. There may be people that want to keep the light bounces on excluded objects.
EDIT: I think thats why I have that glass issue. Hopefully, they add an option to turn of and on bounces from excluded lights.
One might still want to have the light bounce on objects in the included group, so you might not want to reduce the lights global bounces.
Similarly, one might still want light bounces on the excluded geometry from other lights, so you wouldn’t globally reduce bounces in an object’s material.
More options are usually a good thing if thoughtfully implemented.
That said it’s challenging to hit all cases. Like what about glass? If the glass is excluded from the light group, but the object you see see through the glass is included, does the object lose its lighting when viewed through the glass, since it’s now indirect light?
@zeauro Yeah, Like shteeve said, you may need light bounces between objects in the group linked to a light. More options is better for those who might need it.
@shteeve I don’t think the object should lose its lighting. Since the glass is excluded from the light, the light should work on the object as if the glass isn’t there or doesn’t exist.
Same way I think a light linked to a group containing a glass window should not light an object that is behind it that is not in that group.
You mean like a chrome ball behind a glass? I doubt I personally would want to exclude a chrome ball from a light link group containing a glass window.
If I really needed it I would probably make a separate light and add only the glass and chrome ball to it if the need was required.
naw i just meant as another type of light path. like a suzanne next to a chrome ball, if only the suzanne was in the light group, should it be lit in the reflection?
(not that i have a right or wrong answer, its just an interesting case to consider)
All scenes would always have a main light so basically a light that lights everything before you then have the lights that are linked to adjust lighting or modify it. That main light illuminating everything solves that issue.
In fairness, that’s a pretty big assumption that you will always have a “main light”. The whole point of light linking is to give flexibility for unique lighting setups.
Anyway, an option to exclude indirect light paths for objects outside the group would probably be sufficient for most cases and you can toggle it on/off depending on your needs. It’s just interesting to think about since what we think of as “bounce light” is just one type of indirect light.
You can set your scene, inside a sphere with a low res version of HDRI, plugged in a Background shader as its material.
You can make Sphere invisible to Camera, only to light scene and use light linking with it, as a mesh light.
And you can make the World only visible to Camera, not emitting any light.
Good idea. I did think of that but decided to post here about light linking the world as that would be more straight forward, convenient and easier by simply having the light linking tab in the World tab settings instead.
While this is a possible workaround it also renders more slowly and produces more noise compared to rendering HDRI with the World shader.
Light Linking really should be available for the World. I don’t understand how one can design a Light Linking system and forget to include everything that emits light. The system should also include shader that uses any form of Emission.
