Black edges in GBuffer Comping

[instinct]

After switching to R8 for my tests i get unclamped GBuffers now. i compose them all together now and pretty much got every friggin single channel done now. The only problem i'm left with is black edges on refractive and reflective objects. I've created a comparison image to show it. To the left you see my final comp. The middle is RGB Element the right is unclamped RGB.

As you can see both the reflective and refractive objects get pronounced black edges. This is even more appearant in this pic as also reflection filter and refraction filter were used. I multiplied them with the corresponding reflection/refraction channels. is that right at all ? The edges are also visible without the filter tho.

Any pointers would be greatly appreciated.

Regards,
Thorsten

[vlado]

Multiplying render elements is not a good idea as it can lead to edge artifacts. The only correct operation that you can do with two render elements is to add them (even though V-Ray provides render elements that could be multiplied). Further on, you should not use color mapping other than linear. Also, what program did you use to combine the elements? And what antialiasing filter?

Best regards,
Vlado

[instinct]

AA was set to Adaptive Subdivision at 1/3 with and without outline checkbox. What is the correct transfer mode to combine raw reflection and reflection filter then ? as adding them gives pure white on full reflective materials so that cant be right in that case, can it ? I used nuke to comp it all together.


Thorsten

[vlado]

AA was set to Adaptive Subdivision at 1/3 with and without outline checkbox.

Ok, but what was the AA filter?

What is the correct transfer mode to combine raw reflection and reflection filter then?

Multiplication, of course. But like I said, multiplying elements is not a good idea (you will get to edge artifacts sooner or later). It might be better to use the normal reflection element instead, and add that to the final result.

Best regards,
Vlado

[instinct]

sorry got you wrong there...AA filter was set to cubic. When using the Reflection element instead i got the filter already calced in, can i get it out by reverse multiplying the filter ? Bothers me a lil as i'd like to be able to tweal falloffs a bit in post wich would work fine when using the filter and grading it.

Anyways...thanks

Thorsten

[instinct]

i just tried adding the reflection and refraction elements, and they also result in black edges. not as strong as wit raw reflection and filter, but still clearly visible and different from the RGB channel

[instinct]

Here's a difference image of the rendered RGB Element and the final comping. The only problems are on he horizon (that's prolly because of the vrayplane, right ?) and on the edges of reflective and refractive object...everything else seems perfect.



Regards,
Thorsten

[vlado]

I know it's a simple scene, but can you send it to me at vlado@chaosgroup.com for more detailed inspection? I'm out of ideas what may be wrong until I play with it

Best regards,
Vlado

[Joost Ink]

did you render the passes with a black background?

[instinct]

Thanks a lot once more, mail sent

Thorsten

Edit : i didnt render the passes myself. That's how vray outputs them thru render-elements.

[Joost Ink]

i didnt render the passes myself. That's how vray outputs them thru render-elements

I see, but I had the same problem as you discribe, but it got solved when I set my enviromental background to black.

[instinct]

Then i'd be back to the current approach, having to set up multiple scenes to get passes rendered out...

[Joost Ink]

Why?
you could use the vraysky, or whatever you use, as a vray enviromental override. I meant just the max env. background.
curious if that works in your case.

[vlado]

instinct, it will probably work if you use an AA filter other than the Sinc filter. Try the regular Area filter first.

Best regards,
Vlado

[instinct]

i have sent you the latest version. i tried area, cubic and the two new vray ones. And making environment black doesnt make it any better Joost. Am running out of ideas here. Am trying a diff scene now just to have a bit of a change lol

Thorsten