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Packed Prims - attributes not affecting material with sss

Hi folks,

hope my problem is not to silly...

I've attached a test scene below.


I have an object with an attribute "randCol" altering Cd. I pack the object and then copy it several times on a circle.
So far so good. Giving the object a material with some color has the desired effect, having some spheres showing the color more and others not...

Now turning on SSS gives me the effect only on one random picked object, the others render black.

So how would I get the SSS on all the others? In the mantra node I have "Save all materials and shaders" tuned on. In the shader I use "Use packed color"
Do I have to use some "Render State" magic and if yes, how?

Thanks in advance!



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Haven't played too much with Principled Shader, but it looks like the SSS is linked to the Base Color (Cd) parameter. The scattering happens on all spheres, but on your "color_by_randCol" Attribute Wrangle node you've clamped the Cd attribute on all but one sphere to be really dark so it's not really visible.

In your setup you can just use the "Use Point Color" option since the Cd attribute is on the points of your unpacked geometry, not on the packed primitives themselves. Mantra will unpack the packed primitives at rendertime and find the Cd attribute.

Edited by berglte

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Thanks for your answer, but if I try your suggestions it does not work, especially because I had already "Use point color" ticked. So if you just fire a render of my test scene, you will notice all rings have one significantly noticeable blue sphere, if you then go in the shader and activate SSS, all rings get black except on ring, with correct SSS showing.

A friend of mine suggested to throw out the "pack" node and use copy stamp instead with "pack and instance" ticked. That should work.


In my bigger setup, I have a blueberry, which has the same attributes. I write it as a bgeo.sc to disk, then having a RBD sim to place them in a bowl and on a table using a lower geo representation and after that i instance the hi geo on the originally used lower ones.

Here I have the same issues with the above mentioned SSS problems... Still have to dig deeper...

Edited by MrHoo

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