Separate AOV for Bloom Lens Effect

[MannaTheBerserk]

Hello everyone,

Pretty straight forward question: how do I get a separate AOV (render pass) for the Bloom lens effect (or any lens effects and imagers for what matters) out of Arnold?

It seems quite strange not having this simple option available straight away.

Thank you for any help you can give! 🙂

Mauro

[hagen.deloss]

Hi @MannaTheBerserk ,

Thanks for bringing your question to the forums! I'm not sure, but i have asked Lee Griggs to see if he has any insights, i will relay what i hear back! 
 

• I did find this page in the documentation
• I also found this video from a few years ago that might have a few ideas.

I hope this helps, and i will get back to you soon with any additional info i find.

Warm regards, 

[Stephen.Blair]

Sorry, not all imagers out separate AOVs or separate layers.

That's an open enhancement request.

[MannaTheBerserk]

Hi @hagen.deloss ,

Thank you very much for the kind response.

I did watch that video before and also had a good read of that page in the documentation.

Unfortunately, the video only shows how to use the imager, not how to output it as a separate pass.

I'll cross my fingers hoping you will be able to come back with additional info in this regard 🙂

Best regards,

Mauro

[MannaTheBerserk]

Hi @Stephen.Blair 

thank for the answer, much appreciated.

I think this should be a basic feature in Arnold, if anything because having a separate pass for the lens effects is incredibly useful when it comes to the compositing stage.

Best regards,

Mauro

[lee_griggs]

Agreed. A workaround might be to render a separate render layer with just the object that you want to bloom (enable matte or assign a material override to the layer with a black flat shader) and screen it in post.

[MannaTheBerserk]

Hi @lee_griggs 

Thank you very much for your help.

Yes, I thought about creating a render layer just for that, and that's what I will end up doing in the end.

Though, it would still be nice to have the render pass as a more direct, straight forward and streamlined process.

I hope there will be the option some day.

Best regards,

Mauro

[MannaTheBerserk]

So, here are the results of the tests as suggested from you guys.

Assigning a black flat shader as an override does not work, because the lens effect has nothing to work with in order for the effect to kick in.

Same goes for the "Matte" attribute in the Arnold object attributes. Enabling it makes the highlights disappear and prevents the lens effect from working as expected.

Next test, I tried to render out a render layer for the bloom lens effect.

The way I set this up was by assigning a piano black material to all the main objects (which have been assigned to their own render layer), except the one that had a less reflective shader (which was given a more rough glossiness).

With this layer rendered, I color corrected it to make the reflections less visible and the highlights and the rim lights more pronounced (I did not want further reflections on top of those already provided by the reflection pass itself).

The result is not too bad, I would say, but also not perfect either (far from it actually).

I think this need to be added as an AOV in Arnold as a solution.

Thank you very much.

Mauro

[lee_griggs]

Thanks for the update, Mauro. Could you post some images of your renders and your scene? It would help us better understand in which situation you are using bloom in the scene, so that we can answer you better.

[MannaTheBerserk]

Hi Lee,

Sure. I should have done that from the beginning. Apologies for not having thought about that earlier.

It's a super simple scene that I put together just for this test. I am testing compositing render passes from V-Ray and Arnold in Blackmagic Fusion, and that's when I realized the lack of the lens effects pass in Arnold.

Tomorrow morning first thing I will share some pictures for you to have a look.

Thank you.

Best regards,

Mauro

[MannaTheBerserk]

@lee_griggs 

Here are some images that, hopefully, can help.

This is the beauty render:

This is the render passes comp output:

there is quite a difference, as you can tell from the silhouette of the sphere and the cylinder (white bright outline) and the overall brightness and shape of the highlights affected by the Bloom lens effect. 

For comparison, here is a Glare pass from V-Ray (that is how it should be in any standard compositing process):

And this is my Arnold Bloom pass workaround:

It's a reflective material with a facing ratio applied to the specular color attribute, in order for it to eliminate as much of the actual center reflections as possible, and get just specular "highlights".

I hope this helps. Please, let me know if you need more from my side (maybe the Maya scene?). Though, I think that at this point should be pretty clear where the issue is.

Thank you.

Best regards,

Mauro

P.S. also, while I'm here I would like to point out one more thing: I cannot get the glass to produce a drop shadow in Arnold, like the way V-Ray does.

Here is the V-Ray output as an example.

[lee_griggs]

That is very useful. Thank you for sharing!