AOVs and Light Groups

[sharktacos]

I'm wishing that Vray had an AOV system like Arnold does, including Light Groups. This would have at least two advantages over how Render Elements and Light Selects work currently in V-Ray:
1) Having AOVs would mean that if there was a render element in a shader that was not part of the standard set of Render Elements, this variable could arbitrarily be output (AOV). For example the ALsurface shader combines GI and SSS and so 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.

2) The Light Group system allows for each AOV (SSS, Spec, GI, etc) to be output into a Light Group. The current V-Ray Light Select only has "full" making it the equivalent of the beauty pass for those lights, and "spec" so in comp the spec Light Select can be subtracted from the full. This works in a pinch, but it would be preferable to have all of the Render Elements available for each Light Select/Light Group.

The setup for this in Arnold is very simple: you just define the Light Group that a particular light belongs to, and in the AOV section of the Render Settings, for each AOV you check "all light groups" to put that AOV into the defined scene Light Groups.

Something I hope the good folks at Chaos Group will consider implementing in a future release.

[joconnell]

There's rumblings that full LPE's are on the way so that'll sort it! At the minute in work we're just separating each light group to layers and have a little script that'll add each layers lights into a single light select, similar to what you're describing. It's definitely one of the best bits of clarisse though where you can set rules and wild card expressions to build passes and keep everything dynamically updating!

[sharktacos]

Dear Chaos folks, any idea when we might be able to expect LPEs in V-ray? Especially together with light groups/selects, they really are hugely useful. I can make any render element I want, or combinations of them. I also can have all these render elements for any light group/select I want. So complete flexibility. Soooo useful! I know you guys were looking into adding LPEs. Could we get an update or maybe an ETA? Thanks!

[vlado]

Hopefully we'll have something in the nightly builds after we ship update 1 for 3ds Max in a couple of weeks.

In the meantime, can you tell me which specific light path expression are you most likely to use?

Best regards,
Vlado

[vlado]

Btw can you take a look at the extended light select modes in 3ds Max (indirect, indirect diffuse, indirect specular, direct, direct diffuse and direct specular) and let me know if you would like to see them as presets in addition to LPEs?

Best regards,
Vlado

[joconnell]

They're very useful Vlado, it'll be great when we upgrade and can unify our comp workflow regardless of renderer.

Just thinking, with the frame buffer upgrades you're doing, you've got an option to click on an object in the render and load it's material for editing, do you think it'd be possible to add in functionality where a user cloud click on part of the image and be given some kind of generate LPE command? As in if I click on an object's highlight that reflected in a mirror, it'll generate the correct expression for you, giving you a choice of either the object as an lpe tag, the material assigned to it as an lpe tag or just the highlight of the object on it's own? People are going to make mistakes on syntax (myself included), especially when we're doing things like "only the second reflection bounce of a specific light" or other very precise things like that?

[sharktacos]

Hopefully we'll have something in the nightly builds after we ship update 1 for 3ds Max in a couple of weeks.

In the meantime, can you tell me which specific light path expression are you most likely to use?

Best regards,
Vlado

Basically I'd use the LPEs needed to get all the render elements for the shaders used, and then break each of those up into light groups.

Btw can you take a look at the extended light select modes in 3ds Max (indirect, indirect diffuse, indirect specular, direct, direct diffuse and direct specular) and let me know if you would like to see them as presets in addition to LPEs?

Here's a breakdown of Arnold AOVs, Vray RE, and LPEs:

Lighting	diffuse_direct	C<RD>L
SSS	sss_direct	C<TD>L
GI	diffuse_indirect + sss_indirect	C[TD][DSVOB].*
Specular	specular_direct + coat_direct	C<RS>L
Reflection	specular_indirect + coat_indirect	C<RS>[DSVOB].*

When you refer to "indirect diffuse, indirect specular, direct diffuse and direct specular" etc do these correspond to the Arnold meanings listed above, so that, for example, indirect specular=a reflection RE and so on? If so, then first of all, yes they certainly are good to have as presets (i.e. as drop-down options for a LightSelect RE) I'd add that what would definitely be needed in addition to these are sss, direct sss, and indirect sss.

[^Lele^]

They're very useful Vlado, it'll be great when we upgrade and can unify our comp workflow regardless of renderer.

Just thinking, with the frame buffer upgrades you're doing, you've got an option to click on an object in the render and load it's material for editing, do you think it'd be possible to add in functionality where a user cloud click on part of the image and be given some kind of generate LPE command? As in if I click on an object's highlight that reflected in a mirror, it'll generate the correct expression for you, giving you a choice of either the object as an lpe tag, the material assigned to it as an lpe tag or just the highlight of the object on it's own? People are going to make mistakes on syntax (myself included), especially when we're doing things like "only the second reflection bounce of a specific light" or other very precise things like that?

It's a super cool idea, but i think storing the info (100 GI bounces of the LC, alone, when retraced...) would rapidly get out of hand.
Maybe not, though, i wouldn't know.

[joconnell]

Yeah I getcha, I think we only do direct and indirect so it might go as far as the reflection of an object in a thing rather than the bounce of a bounce of a bounce (I'd imagine those would get so dirty as to be unusable?)

[lazarin_kouchev]

Hi, we have the same issue regarding the LightSelect in Maya. The "full" option is suitable for subtracting lights from the beauty, but not from single render passes. These extended Light Select modes in Max that Vlado mentioned, are those available in Maya with Vray Next? If yes, i can't seem to find how to enable them! Having all the elements separated where the light contributes would be immensely appreciated!
Lazarin Kouchev
NuBoyana FX