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Trace Set not working with SSS Shaders

Message 1 of 6
352 Views, 5 Replies

Trace Set not working with SSS Shaders

Hey There,

I have a simple scene of 2 cubes and an area light. I have setup my trace set so the green cube should not cast onto the red cube. This works as intended with a standard surface with no sss, but when I add sss, it no longer works, see reference images:


Working trace set - no sss on red cube:



SSS on red cube breaking the trace set:



However, if I set the object to be thin walled, the trace set begins working again.

Here is the very basic shader setup on the red cube:



Is it possible to use an arnold trace set in conjunction with non-thin walled SSS shaders?

This happens both in maya and katana

Thank you



Message 2 of 6

Added detail, this is using MtoA and KtoA, Arnold

Message 3 of 6

Hello arnold_user123


SSS doesn't use the trace_sets mechanism, SSS uses the sss_setnames

// Stephen Blair
// Arnold Renderer Support
Message 4 of 6

SSS_setnames as I understand it refers to unifying several objects' ss properties to aid the blurring/smoothing at intersections

Does this mean if I want to achieve the same affect as the first image, removing the shadow being cast from an object onto an sss object, that is not currently possible?

Message 5 of 6

SSS doesn't use the standard trace sets, so no.

// Stephen Blair
// Arnold Renderer Support
Message 6 of 6

Is there another possible way to achieve the same effect, without trace set? Perhaps with a ray switch?
I know I can turn off shadow casting for an object, but that stops casting from that object onto any object, as opposed to a specific one. Same with a ray switch

If anyone has any ideas that'd be great!

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