Marmoset 4 SSS problem rendering with raytrace

elle_art · Feb 2021

Hi guys, i`m new here

I`m using marmoset 4 to render my character (has udim uv, for best resolution maps) and i setup one material for each udim.

It`s working with raytrace turn off, but when i turn on raytrace, appears a line where the material ends.

Anyone knows how to fix this?

raytrace off

Image: https://us.v-cdn.net/5021068/uploads/editor/sk/kkaajj0jz597.png

raytrace on

Image: https://us.v-cdn.net/5021068/uploads/editor/xf/f6o99kda80dx.png

uv layout/udims

Ps.: Sorry for the terrible english...

EarthQuake · Feb 2021

When ray tracing is enabled, each texture set is effectively treated as a unique mesh object. This can cause some seam artifacts along the material borders. We are investigating potential fixes for this, but for now, it is a known limitation.

A workaround would be to remap the UVs so they are all on a single texture set/use a single material. The easy way to do this would be to combine the maps in Photoshop. For instance, if you have 8x 2x2K textures, you could create a single 8x4K texture, and move/scale the UVs accordingly to match up with the new layout. There was a recent thread that went into more detail about this process: https://polycount.com/discussion/224230/toolbag-4-ray-tracing-render-shows-uv-seams#latest

PS: there is a significant amount of wasted space in this UV layout, so you may be able to remap the UVs to a single texture set and bake the textures to the new layout while retaining the same amount of texture detail, but using a texture that is probably about half the size. UDIMs don't typically provide many benefits for an asset like this until you need many 16K textures, as you may run into hardware issues when using 32 or 64K images.

NhodgesVFX · Feb 2021

@EarthQuake is it possible to have the user assign a group value on the material or mesh then materials or mesh with the same group value are considered the same mesh by the raytracing engine. I believe this is how Arnold solves this problem with its engine. Blenders cycles also doesn't feature this issue so maybe you could look their as well.

EarthQuake · Feb 2021

NhodgesVFX said:

@EarthQuake is it possible to have the user assign a group value on the material or mesh then materials or mesh with the same group value are considered the same mesh by the raytracing engine. I believe this is how Arnold solves this problem with its engine. Blenders cycles also doesn't feature this issue so maybe you could look their as well.

Yeah, we've got some plans here, which we hope will allow us to solve this without any additional user-facing options or controls. The crux of the issue is how the trace backend data is stored, and there are some changes we're planning to add which should allow us to be more flexible in combining some of that data for cases like this.

Sreliata · Feb 2021

I had this issue before as well. The only way to currently fix this, seems to be to adjust the UV and textures to be on one UV -Set and ONE texture only, so that it's all "one" part.

I hope this will get fixed in the future, since Blender Cycles, nor Arnold and other programs do seem to have this issue at all. It would be super convenient not having to re-do everything !! ^.^

Marmoset 4 SSS problem rendering with raytrace

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