Arnold Volumes Object ID type of AOV?

[Perry Harovas]

Hi all,

Sorry to ask this here.

Have asked in other places with no real response.

Does anyone know if it is possible to have Arnold output

what is essentially an object ID pass (different colors for each object)

but for volumes within Arnold?

I have some VDB smoke, then some other smoke in a different VDB.

They both use different Volume_Collector shaders with different settings.

Is there a way to spit out a pass that shows me the volume, but lit flat

so I can use it as an object ID mask to tweak inside of Nuke?

I can get all the geometry in the scene to output a Object ID AOV

except the volumes. They are rendered lit with shadows and lighting colors, etc.

Without having to render a totally different pass, is there a way to output an AOV

that can isolate the volumes, each one differently with a different color for each volume, so I can tweak them independent of each other?

I can use the Volume Opacity AOV, but it outputs ALL the volumes as one color (white, with transparency) in the resulting AOV. This would be perfect, if each volume had a different color, not all the same white color.

Hope this is clear.

Thanks for any help!

Perry

[Jason S]

Are you exclusively using pure Red Green Blue (and Alpha) as your tile colors?

(or are you using deep images?)

Because otherwise you cant use object ID colors to isolate elements of variable opacity midpoints (inherent to volumes) to get something like this (below) once isolated.

  

For the same reason (non-deep) arbitrarily colored objectID images are typically rendered at 2X+ size, to extract grayscale tiles (white (1)  OR black (0) )
and then resize down to have antialising midpoints around edges of isolated elements.

Or perhaps not as convenient as for all other elements with ID's, but how about just setting-up a pass for your volumes with all objects black (with black alpha)?

[Jason S]

This may be of help if Deep Exr's are an option:

http://jokermartini.com/deep-compositing-101/
http://jokermartini.com/deep-compositing-102/
(shown using Vray for 3dsM but should apply to anything)

 

They Mention that deep can be slow, and it really can be much slower, but the benefits can still make it worth it.

Quote:
There are many benefits to compositing with Deep Image EXR’s such as no edging errors, 3D depth data and having more information to manipulate the digital images. The main drawback is that the image files can become very large and slow to composite. Below is an image showcasing the errors produced when compositing ‘Non-Deep Image EXR’ compared to ‘Deep Image EXR’. If you view the image below full screen, you’ll see the edges which overlap the middle teapot have a slight glow around their edges. Comparing that to the image on the right, you’ll see there is no glowing edges, making for a correct result after color correction. I drastically changed the color of the middle teapot to blue. You can see below the left image is full of errors while the right image contains no errors.

On 08/31/15 22:13, Jason S wrote:

Are you exclusively using pure Red Green Blue (and Alpha) as your tile colors?

(or are you using deep images?)

Because otherwise you cant use object ID colors to isolate elements of variable opacity midpoints (inherent to volumes) to get something like this (below) once isolated.

  

[Perry Harovas]

Totally forgot about deepEXR.

Yes, this is an option.

Thank you so much for jogging my brain,

I really appreciate the help!

--

Perry Harovas
Animation and Visual Effects

http://www.TheAfterImage.com

-25 Years Experience

-Member of the Visual Effects Society (VES)