Light Path Expressions for custom AOVs

I think Cycles doesn’t denoise passes at all yet-- only the beauty pass. AFAIK this isn’t a limitation of the denoise system, just an unimplemented feature that hasn’t become a priority yet. Could be wrong, but this was certainly the case last time I checked. Same thing with baking.

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I’m really happy to see that someone is actually interested by LPE. I’m a student I come from an other software and I’m working with blender since one and half year now. I can assure you that custom light aov miss me a lot. That’s not only for tech. For me it’s also for artist. I want to be lighter Artist and technical Artist and when I do lighting custom light aov allow me to check which light does what and how this light is affecting the entier scene. That’s give me more control and precision in my work. Also it’s completely usefull for rendering. Like that we can for example have more possibility in our compositing. I think blender have a lot of work to do in Lighting because some really cool feature are missing (or maybe I did found it inside blender). In any case thanks @c2ba to working on this.

Also sorry for all possible mistake with my English :slight_smile:

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While it’s not LPE or custom AOV you can use Light Groups for what you describe, they are not in master yet, they will in the near future hopefully, but you have them in our build, you can get it on graphicall.org :slight_smile:

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Hi everyone! I know it’s a little bit old topic but I would like to know if their is any news about LPEs from @c2ba or from @brecht. I’m trying to look everywhere about LPEs (custom light aov like in Arnold for example) and found nothing.

This is a huge missing in blender I think. I’m currently working on a custom add-on to give more flexibility in lighting, like light editor or few little features but LPEs (this what I call light group or light pass aov) are the big one which are missing.

Would you think that would be possible to implement? LPEs are they under study?

In any case thank to all people involve in that discussion :slight_smile:

Hi @Eqkoss,

let me introduce myself: I’m Lukas, currently studying animation & VFX and I would also love to see LPE or other light tools being implemented in blender. Currently there is this AMAZING branch from @JuanGea . He mentioned it one post before. It already contains the lightgroup feature where you can export the influence of single lights to a render pass. It’s a little bit like an aov in arnold. Did you already try it?
You can download it right here: https://blender.community/5fa1a5759c12216992449167/download/60756bff9c122131b3cae2f0
JuanGea also has this demonstration of lightgroups in blender: https://youtu.be/GXzmReUUU34?t=1559
I struggled to find the download link to the Bonemaster build. It’s the small green download button at the top :sweat_smile:
It’s pretty easy to click on the big github link and overlook the download button. I did this… a lot… And tried to build blender and failed. A lot.

I hope I could help you a little bit.
I suspect this feature gets implemented with further improvements to Cycles X.
For now we need to rely on to the BoneMaster branch. (Thank you JuanGea

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2.93 and 3.0 are not up to date, I’ll update them as soon as I have some spare time, we are now working with 2.92 :slight_smile:

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Hi! Thanks @cglukas for all this information.
I still know about the branch from @JuanGea. I try to downlaod it in the past but I sttrugled to found the link to ahah. I also try to build it by myself but failed too so I let it go… I will give it a new try. I’m little afraid about branch. I prefere to stay in the master, that also why I want ton stay in.

Also I’m now working in a studio and lot of people want to use or try blender but not without LPEs. This is the reason why I also think Blender Developer should give a big interest to it.

Yes! you help me so thanks and I also hope this features get implemented to cycles X. This will be a good opportunity to do it and the right time.

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Sorry to bother, but will it work with OSL?
Currently AOVs in Blender not working in OSL, which is a pitty // that why i ask

Hi, I just posted a proof of concept patch for this: ⚙ D15972 [Proof of Concept] Cycles: add support for light path expressions

It is a bit lacking in the user experience side of things, and some features might be missing.

You can render LPEs by adding an AOV and setting the type to “Light Path Expression”. There are also some settings on the objects to add a light path tag to them, which emulates light grouping, but is a bit more powerful.

I am open to any idea on how to improve the UX and workflow (let’s keep any discussion in this thread).

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Could this be a way to seperate environment lights as well or would that be part of a different task?
I usually like to setup a few different HDRIs in one lookdev template to test assets under various lighting conditions. That way I can render it all in one render job instead of a job for each environment.
Either way, looking forward to try it out!

I imagine that for that we need to have multiple environment / worlds support, this is something I talked about with @lukasstockner97 for light groups, however I think it was not an easy thing to do.

@KevinDietrich thanks for this, super useful!

@irfan, @JuanGea Indeed, this would not be any different than light groups for that particular case.

What is essentially asked is to have an easy way to render multiple times with different settings. This is more of a pipeline issue. Even if you could have N worlds, you would still need to render N times the samples for the same quality, so, in fine, N renders.

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Yes, multiple environment / world support in lightgroups is what I was looking for.
Sure, it does take longer to render but still cheaper then rendering them seperately.

@KevinDietrich will there be a build of the current state of LPE?

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Yes, you have to render the samples for those extra environment, but you don’t have to repeat the samples for all the lighting, I mean, it’s not the same to render this:

2 worlds + 3 lights

Than:

1 world + 3 lights + 1 world + 3 lights

Also take into consideration the hasle of additional file management, and pre-load times, and specially when we talk about animation.
I think it’s very useful, but I assume some additional work is required based on what I talked with @lukasstockner97 back when he was finishing the light groups implementation.

:slight_smile:

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Are we finally talking about having world as one (or more) Light object in the scene??

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Awesome, thank you for your incredible work Kevin! Your contributions to Blender and Cycles are really making my job of pushing VFX studios to adopt them much easier :slight_smile:

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I asked in the chat not long ago about that regarding light linking, and Brecht agreed that, while there is no timeline for it, when light linking starts to get implemented, it will be important to consider either treating the world as an object or supporting a multi-world workflow.

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it will be important to consider either treating the world as an object or supporting a multi-world workflow.

I really hope they go with treating world as a light object.

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I do too. Anyway, I was paraphrasing, since it was a short answer I didn’t want to give the impression that their mind was set on anything particular, it was just a brief comment on his part.

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I think I saw such thoughts on Brecht’s part somewhere on the forums too. I believe it makes more sense to turn world shading into Environment/Dome light type object. It just makes more sense in the lights of new changes for light groups and for other reasons as well.

I hope they do that.

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