comping diffuse passes creates "halo" white edge error

[sharktacos]

In theory the totalLight pass should be the same as the diffuse multiplied with the RawLight so:

diffuse x RawLight = totalLight

However when I do this in Nuke there are significant errors (white edges or "halos" on objects). (FYI I am working in linear using non-clamped multichannel EXR)

This is a bummer because it means that the lightSelect passes become pretty much unusable. (Please correct me if I am missing something here, I'd love to be wrong about this!)

Is there any way to fix this? It seems that Vray must be doing something different than Nuke since the totalLight does not have this issue.

[Morbid Angel]

you need to add unpremult (all) node infront of your tree (from multi exr) and then shuffle in the alpha at the end of your tree and premult all by that alpha. This should fix the halos or any black edges.

[sharktacos]

you need to add unpremult (all) node infront of your tree (from multi exr) and then shuffle in the alpha at the end of your tree and premult all by that alpha. This should fix the halos or any black edges.

Thanks for the reply. In this render the alpha is pure white and fills the entire frame so because premult affects the alpha it has no impact here. I've attached an image that illustrates the error. You can see the white edges around the red lamp base and clock:

[svetlozar.draganov]

Would it be possible to attach Render Elements / Maya File(+assets)/ Nuke file ?

[sharktacos]

Would it be possible to attach Render Elements / Maya File(+assets)/ Nuke file ?

I can email something to support for you guys to look at.
I did find a workaround that seems to fix it:
totalLight divided by diffuse = new Raw Light.
Note in the attached image that the resulting raw light looks markedly different from the raw light render pass.


Then I can use this to recreate the total light without the edge error:
new Raw light x diffuse = totalLight

and properly insert a color correct:
(new Raw light + CC) x diffuse = totalLight

This workaround seems to solve the issue, but it makes me suspect that there may be something off with the passes generated by vray. A least that is, the math appears to not be working back and forth with multiplying and dividing these, so there's a "fly in the ointment" somewhere in there. I'll send the scene so you guys can investigate.

[svetlozar.draganov]

Hello,

Thank you very much for the scene and the files you sent us.
Unfortunately Raw-Render-Elements in Vray produce such artifacts in compositing.
You have informed us that you have found how to fix this issue, but we would like to let you know that this issue also appears on all Raw-Render elements.
The easiest way to fix it by maintaining the usage of Raw-elements , is to avoid Vray-Raw elements and generate them from non-raw elements.

For example:
Lighting / Diffuse = Raw Lighting
GI / Diffuse = Raw GI
Reflection / Reflection Filter = Raw Reflection
Refraction / Refraction Filter = Raw Refraction

If the above workflow is used to generate Custom Raw-Render elements - this issue won't exist.