How to mathematically composite the V-Ray Lens Effects to match the Beauty pass?

[TomasEsperanza]

Hi,

 

V-Ray creates these render elements, but which ones to use in the comp, and with what blending modes?

 

LensEffectsSource

Bloom

Glare

BloomMask

GlareMask

 

I can get close to the RGB_Color pass but not match it...

 

If you actually know for sure, what the correct way to do this is, please do share

Thank you

 

T

[Nicolai Bongard]

As far as i know: The bloom/glaremask is just to show you where in the picture you get bloom when you set an intensity limit to your bloom/glare. The bloom and glare is your rgb plus the bloom/glare in seperate files. In the lens effect settings you can set it to apply to image+render element (applying it to your rgb and giving you a separate image with rgb plus the isolated bloom or glare), just image (just your rgb with the bloom/glare/both applied) or i guess just render element (giving you rgb + bloom or glare in separate files). So in theory you should just need to set it to image as you want it applied to your rgb, and since it is a post effect you can apply and adjust it to your final render so there should be no need to add it in photoshop or whatever you happen to use later on in postproduction. Cant really help you with how to go about comping it in post, sorry!

[TomasEsperanza]

Thanks for that Nicolai.

 

Having experimented some more in PS, it appears that one can simply set both the "Bloom" and the "Glare" passes to ADD, then reduce their respective opacities to control each effect. (This allows me to control their contribution with a natural result). So it's not a case of just finding the correct blending mode, as the effect seems to be rendered at full strength for compositing flexiblity. (Well Multiply didn't work anyway).

 

I guess the "Mask" layers V-ray offers are not for comping but just for assesing the parts of the image the bloom and glare are reacting too when adjusting them in the 3D app.

 

Ultimately, when compositing, the value of these bloom and glare passes may be relative to how much the preceeding layers affect the overall comp; if the basic comp is drastically changed then the bloom and glare would cease to match it, (although I guess this is unlikely). In this case I suppose one would resort to common Photoshop tricks to recreate bloom and glare effects, such as duplicating and blurring layers, or using MB Looks.

 

(Personally, I would prefer to avoid baking the effect into the RGB_Color pass when rendering for a comp.)

Edited June 15, 2015 by TomasEsperanza

[Scott Schroeder]

I think the layers need to be set a difference. I'm not near PS to test but if you search the vray forum Grant Warwick asked the same question. I think Vlado calls it additive but the layer function in PS is difference.

[TomasEsperanza]

I think the layers need to be set a difference. I'm not near PS to test but if you search the vray forum Grant Warwick asked the same question. I think Vlado calls it additive but the layer function in PS is difference.

 

No it's definately not "Difference" (unless you're making rainbows ). The red herring there is that Photoshop nomenclature gives us "Linear Dodge (Add)", (but I find most just call it "Add").

 

So as I said, it appears that if we take the Glare pass and the Bloom pass and "Add" each respectively to the comp, it is just a matter of dialing down the opacities to control each effect's contribution. We can ignore the other passes as these aren't even controller passes (useful masks etc.) let alone content passes.

 

Prior to using these effects I was just looking for affirmation as I'm not clear on the maths behind these passes, but I have added the bloom and glare to a beauty now without any visible issue resulting from the method, so I guess that's how to composite them. On reflection though, they don't seem that useful (as opposed to adding post effects available in PS), due to the fact these effects are pre-rendered and wouldn't represent appropriate bloom and glare for a significantly changed composition (which after all is the point of bothering with the compositing workflow). Still, good to know anyhow.