V-ray light select, render to passes but without PDPlayer?

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  11 November 2012
Lightbulb V-ray light select, render to passes but without PDPlayer?

I was on a Vray the other day, and was presented a technique which can be seen presented here:
http://www.youtube.com/watch?v=VQISe90BzHg

Can this overlay method, trixing back and forth be done in Photoshop instead of PDPlayer?
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  11 November 2012
Yes. It's just a render element like any other. So composite it as an 'Add' layer in PS.
 
  11 November 2012
Originally Posted by musashidan: Yes. It's just a render element like any other. So composite it as an 'Add' layer in PS.


Thanks for the explanation.
How do you suggest to adjust over-exposure?
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  11 November 2012
If you mean overall scene exposure, I usually use the vray physicalcam and adjust the f-number/shutter speed/Iso settings.

In later versions of vray you can also use EV exposure control fom the environment dialogue the same as you would for mentalray.
 
  12 December 2012
Hello again,

lets leave the exposure question for later.

I have now extracted some render elements. Two light sources through VrayLightSelect and a bunch of other elements: VRayDiffuseFilter, VRayGlobalIllumination, VRayRawGlobalIllumination, VRayLighting, VRayRawLighting, VRayReflection and VRaySpecular

I am sure I might have rendered out more elements than necessary. I did it mostly to see how they look like.

But basically, what I need now is to know how I set up an image base without lighting so that I can overlay (Linear Dodge (Add), right?) the two separate light source elements that I got through VrayLightSelect.
Basically an RGB pass minus the lights.
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  12 December 2012
A simple version would be:
result = vrayreflection + vrayrefraction + vraygi + lightSelectA + lightSelectB

You can adjust the strength of the lightselects to whatever you want. Note that GI and reflection are not inlcuded in the lightselects so you usually can't leave them out completely because their influence can still be seen in those passes.

If you have other lights in the scene that are not included in the lightselects and you have not split up the lights into a separate diffuse and specular light:
a = refl + refr + gi
b = lighting + specular
c = lightSelectA + lightSelectB
result = a + (b-c) + c

This is missing other passes like SSS and self-illumination, but those are additive as well.
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  12 December 2012
Originally Posted by Rens: A simple version would be:
result = vrayreflection + vrayrefraction + vraygi + lightSelectA + lightSelectB

How comes that you didnt add Diffuse to the list?
I made a quick test, overlayed all those you mentioned with GI below and they ended up identical with the RGB layer. But I am surpriced that the diffuse wasnt needed. Maybe its because its a basic test I did?
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  12 December 2012
Originally Posted by Rens: You can adjust the strength of the lightselects to whatever you want.

In Photoshop, I can lower the strength by lowering the Layer Fill percentage. What if I want to to increase it?

Originally Posted by Rens: split up the lights into a separate diffuse and specular light

if I would've had lights that were split up into diffuse and specular lights, which passes will each of them affect? I am asking, since neither diffuse nor specular was mentioned in the first result example, vrayreflection + vrayrefraction + vraygi + lightSelectA + lightSelectB.

Originally Posted by Rens: ... result = a + (b-c) + c

In that case how does the minus work? I understand that + in Photoshop is Linear Dodge (Add).
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  12 December 2012
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