Vray light select- issues and how to use it

[GidPDX]

First of all, the light select render element is missing from the main render element drop down in the UI! You can only get to it through the shader tree, OR through schematic.

The problem with adding it to schematic is it then does not show up in your shader tree!?

OK, those two issues out of the way, now on to the weird work flow to get them to see groups of lights:

1) make a work space in schematic- give it a name that makes sense

2) make your new light work space the active one

3) with the item list open (because you can't drag lights from the shader tree for some reason), drag in the lights you wish to group for the light select render element

4) select the light select render element in the shader tree and find the workspace you put the lights in, in the drop down for included lights.


So my question to Chaos Group is why did you choose to use schematic work spaces instead of groups, and when will the light select render element be added to the main UI drop down for render elements?

[GidPDX]

I guess it's mentioned here how to add it but I think the entries on light select could be stronger.

https://docs.chaosgroup.com/display/VRAYMODO/3.40.01

[vladimir.nedev]

First of all, the light select render element is missing from the main render element drop down in the UI! You can only get to it through the shader tree, OR through schematic.

That UI is mostly designed for render elements that have a single instance (in most cases).
You can't create more than one instance of a render element with it.
After you create one, the middle button turns into a disable/enable all outputs of that type.
The light select usually has multiple instances for different lights/groups of lights.

I guess it still makes sense to add the light select there, so you can quickly select/enable/disable all of them.
Maybe I can modify the middle button somehow, so it can create more than one output of a specific type, if the user needs that. But this will be optional behavior.
I will log this as an issue.

The problem with adding it to schematic is it then does not show up in your shader tree!?

It should go in the Nodes folder in the Shader Tree.

OK, those two issues out of the way, now on to the weird work flow to get them to see groups of lights:

You can use any type of group with the light select, not just workspaces.
Internally all types of groups (workspaces, assemblies, render pass groups, normal groups, etc) are the same type of item, so the light select doesn't even distinguish between them.
You can also use group locators (which live in the Item List and is another type of item) as well, if that's more convenient.

You can also connect multiple lights or groups using the Schematic, which is similar to how the Replicator Prototype connection works.



Greetings,
Vladimir Nedev

[GidPDX]

I've never been happier to be so wrong! Thank you Vladimir!

I should have known better to ask what the intended function for this feature is before making so many assumptions. Apologies!

Where is this work flow listed in the documentation?

I've taken the video down and will make a new one with this new information soon if there is no documentation covering the work flow.

The only small bug/issue I've found is that the light select will not create a render elements folder and be put in it if you haven't already added another kind of RE. It ends up just getting placed under where ever your selection is in the shader tree. This is to be expected though when using add layer, but I think it makes another argument for adding it to the RE panel drop down as well.

[vladimir.nedev]

As for how to use it when compositing (since this was asked in the Skype group).

I think you just need to subtract the light select from the RGB element, and then add it back with any color grading you might want.
You can do this multiple times for each light select.

It works better in RT GPU, because in this case the light select includes GI and reflections coming from the light, so my example images use RT GPU.





Here is the test scene and NUKE script.
light_select_comp.zip

Greetings,
Vladimir Nedev

[GidPDX]

Thanks for the breakdown and the tip on RT GPU vs. CPU!

Setting up such light passes and maintaining them in MODO's render engine is fraught with danger and in my opinion and a PITA, so this is a VERY welcome feature in Vray.

[BVA]

Vladimir, thanks for the breakdown and explanations! I really find these helpful!!!!

as for the light select element, I tried to add 3 different lights to 3 different light select render elements, and then I wanted to have ALL my other lights on a seperate render element.
Would it not be possible to add a light select element and attached the 3 light to it and say "exclude the attached" then it will automatically render all other light to that element. (I hope this makes sense)

[BVA]

Vladimir, I still cannot get the light select elements to render in a scene...if I drag the ligths to a new scene they render fine. I am sending you the scene, please can you tell me what I am missing here?

[vladimir.nedev]

Vladimir, I still cannot get the light select elements to render in a scene...if I drag the ligths to a new scene they render fine. I am sending you the scene, please can you tell me what I am missing here?

There is a bug with the light select in combination with probabilistic lights.
I think it's already fixed in the main dev branch, but I haven't fetched those changes.
You can disable the probabilistic lights option as a workaround.
It probably works in a new scene, because there are less lights and they can all be sampled non-probabilistically.

The change-log will include a mention of this fix.

and then I wanted to have ALL my other lights on a seperate render element.
Would it not be possible to add a light select element and attached the 3 light to it and say "exclude the attached" then it will automatically render all other light to that element. (I hope this makes sense)

Wouldn't it be better if the option was "Include all lights without light select element", so you don't have to select anything explicitly ?
As you create light select elements for those lights, they will get automatically excluded, if the option is checked.

Greetings,
Vladimir Nedev