Xgen render artifact

[blaabjergb]

Hi guys,

So I am rendering a turntable of my groom to see how it looks, but for some wierd reason I get this square in the middle of my render *artifact* where the hair doesn't render the same as everywhere else. If I cank the samples up a lot it renders normally, but with lower samples that square is almost see through, and I swear that the Xgen groom goes all the way through without any wierdness happening around that area, it shouldn't be there. What's my problem?

I am using the latest Renderman.

Here is a video turntable of the hair, the cube artefact at the back of the hair is very visible:

https://www.youtube.com/watch?v=w6LrcBBhldc&feature=youtu.be

I uploaded an image of my problem render.

The xgen groom is definately tight enough arund that square, it shouldn't be see through.

Bjørn

[sean.heasley]

Hi @blaabjergb

By chance could you try a different renderer like Arnold to see if this issue still occurs?

Also, if you hide the face during the render but keep the xGen groom does it still appear?

Let me know if anything changes!

[blaabjergb]

It's true, it is only happening with Renderman, Arnold works fine it seems.

I can't use Arnold for my project though, because the batch render support is not very good with the standard license.

At least I know that it's Renderman...

[mspeer]

Hi!

Please make sure if it's XGen.

- Disable all other elements in the scene.

- Also disable some render / material feature to see what feature  causes the problem.

- Do you use a Renderman Shader for the hair?

[blaabjergb]

Ah yes, it only happens with renderman.

Like I said, Arnold works fine.

Interestingly, if I offset the character so that the hair is not part of the first bucket rendered, it's fine.
It almost seems like Renderman doesn't register the xgen geometry for the first four to five buckets that it starts out with in the center of the image, and that creates artifacts that are bettered with each pass.

[blaabjergb]

Here is a 20 frame render of the camera moving past the character, it's very evident when the character passes the center of the camera view, that the artefact appears.
It only happens in the middle of the rendered frame because only the first four to five buckets ignore the groom, and they only do it the first time. Second pass they will regonize it, but by then it's already ruined.

[mspeer]

Hi!

You could try different settings for Render Options:

https://rmanwiki.pixar.com/display/RFM/Advanced

[sean.heasley]

Hi @blaabjergb

Did the suggestion @mspeer made about tweaking the render options help at all?

[blaabjergb]

Hi guys, thanks for all the help thus far. I haven't found the answer as much as a temporary workaround. 

I found that the first around buckets rendered don't include the Xgen hair, however I can change the bucket render order from spiral to horizontal, which means that Renderman starts rendering the first buckets away from the center of the image, which reduces the likelihood of hair being present in that area.

It's a bit of a workaround or hack, so hopefully I won't need to render full frame fur or hair.