Light Path Expressions

[joconnell]

hey. aaaaa AOV do have a speed hit! there not free!( okey nothing crazy like 2x but still a speed hit)

And as to to light select is dosent support refraction! is there a way to get that added?

Which aov's do you typically use? The standard ones I have don't add much if any time at all. In terms of light select and refraction, the light select element is designed as only the direct diffuse light that comes from that light - by refraction do you mean having a light select for light that's seen through a glass object?

[vfxronin]

LPE will have an effect on the rendering performance for sure, because we'll have to evaluate if a path matches given LPE.
The more expressions you have and the more complex they are the slower it will be.

The real question is which practical problems you can solve with LPE and you cannot solve with the current hardcoded AOVs.
If you answer this question, then we can think about some solution or even consider implementing LPE.
Until then we have no big incentive to invest time and effort in implementing LPEs.

It a response to the shift in VFX and animation of how renders are been feed to comp. the methods of aov editing are changing, the current aov set will over right more then just lighting wich including the shaders as well each animation VFX house have ther Owen methods of dealing with CG.

But they all shear a comma goal. To editing lighting in comp with out changing the shader. This help to pass changes between shots and back to lighting, if I edit the current aov sets in Vray I won't be able to esyily pass it to a nothere artis or back to lighting to implant on a sequence leve.. This also counts for pipe intergration as most people are not a fan of rewriting shader aov set to make it work in There pipe. As morse places are now becoming more depends for multipal renders to accomplish the work. It also allows to write shader aov for sequence on the fly..

[t.petrov]

vfxronin:
I'm not getting something in your description.
As far as I understand the LREs - they are a way to describe an AOV, right?
So if instead of writing LREs you can add a diffuse, N light select, M material select or whatever hardcoded AOVs we have, then what is the difference?
If you've not added a LRE element in the scene before you've rendered the scene then it won't magically appear, right?

[vlado]

Of course there will be a separate render element to contain the results from a given light path expression, but LPEs are a bit more general than what we have now. For example, you can specify that you want a render element that contains all contributions of a given light, reflected from a given object and refracted through a given other object, and any such combinations.

Best regards,
Vlado

[vfxronin]

Of course there will be a separate render element to contain the results from a given light path expression, but LPEs are a bit more general than what we have now. For example, you can specify that you want a render element that contains all contributions of a given light, reflected from a given object and refracted through a given other object, and any such combinations.

Best regards,
Vlado

actually i would love to see a example of this if you can post one Vlado

thanks you

[vlado]

actually i would love to see a example of this if you can post one Vlado

Well, we don't actually have LPEs right now, so I can't

Best regards,
Vlado

[joconnell]

It a response to the shift in VFX and animation of how renders are been feed to comp. the methods of aov editing are changing, the current aov set will over right more then just lighting wich including the shaders as well each animation VFX house have ther Owen methods of dealing with CG.

But they all shear a comma goal. To editing lighting in comp with out changing the shader. This help to pass changes between shots and back to lighting, if I edit the current aov sets in Vray I won't be able to esyily pass it to a nothere artis or back to lighting to implant on a sequence leve.. This also counts for pipe intergration as most people are not a fan of rewriting shader aov set to make it work in There pipe. As morse places are now becoming more depends for multipal renders to accomplish the work. It also allows to write shader aov for sequence on the fly..

It might help to clarify what your definition of an AOV is and what and LPE is. If you use LPEs and edit them in comp, you can break the physics of a render in many ways that you can never pass back to 3d. If you use AOV's / Render passes then you are able to.

[vfxronin]

It might help to clarify what your definition of an AOV is and what and LPE is. If you use LPEs and edit them in comp, you can break the physics of a render in many ways that you can never pass back to 3d. If you use AOV's / Render passes then you are able to.

I think I'll need to make example if this. My dyslexia is helping me here .

I'll have some examples ready as soon as I finsh this show

[vfxronin]

hey, so i would like to back track on this a bit! it look like LPE may be a bit of a over kill for what i was asking for but may be usefull to have in the futter or a vray alliterative!

[glacierise]

Hi guys,

We're very interested in getting LPEs in V-Ray - let me know if there's anything I can do to help - testing things or listing use cases, etc.

Thanks!

[yolov]

Hi guys,

We're very interested in getting LPEs in V-Ray - let me know if there's anything I can do to help - testing things or listing use cases, etc.

Thanks!

Oh, once we get to a point where we have something to show, there's no doubt we'll let you know

[sharktacos]

Just to throw this into the discussion here, from another thread (https://forums.chaosgroup.com/forum/...d-light-groups), two current limitations of the Vray Render Elements are:

1) The ALsurface shader combines GI and SSS and so (as Vlado has explained elsewhere) needs to have different Render Elements than the standard ones (i.e. it needs to have SSS_direct and SSS_indirect(GI) rather than just SSS and GI. The solution would be to have a flexible AOV system which is derived from the shaders (like Arnold has), rather than a fixed set of REs like we to currently in Vray.

2) The current V-Ray Light Select only has "full" making it the equivalent of the beauty pass for those lights. It would be preferable to have all/any Render Elements available for each light set. Rather than having this in the attributes for the Light Select RE (i.e. needing to create a Light select RE for every desired AOV which would be quite tedious), it would be better to have an option in each RE to include it in a Light Select. Again the Arnold GUI here is worth looking at.

FWIW, neither of these, to my understanding necessitates having LPEs. nor would it affect render times. It's simply re-vamping how things are organized to be more flexible and easier to manage.

[glacierise]

sharktacos LPEs are important for much more than conditional etc light selects - they would give us just the right bunch of rays we need. Sometimes it's the reflection/GI from specific objects, other times it's the shadow cast by specific geometry, or a combination of conditions, like 'reflection rays who hit the environment after refraction from object X'. It's cool stuff, would be great for V-Ray to have them!

Cheers

[joconnell]

Great for very specific denoising!

[glacierise]

Yeah and not just that - getting object or material ids for not just the camera rays, or any super specific custom frame buffer which is so often necessary in production.