View Full Version : SSS and cluster Materials. Anyone?

06 June 2006, 03:36 AM
I'm mapping a character now and instead of using a single texture for the entire body, i've clustered parts of the body and have a map for that part of the body.


Clusters would be

Arm Left
Arm Right
Leg Left
Leg Right

SSS doesnt appear to work well when you apply it as a material on each cluster because it doesnt take into account the faces that arent in the cluster. So imagine the chest cluster with a SSS material, the Chest cluster does not contain the polygons that make up the back of the character. If you were to take a sphere and cluster half of it as "front" and half of it as "back" and apply SSS materials to each cluster.... When you render it, it will be discontinous, meaning the SSS will ahve a seam and one side will be brighter than the other.

Any ideas on how to apply SSS to this character in this situation??

Render passes?

Whats the best way to add in SSS when doing a seperate SSS pass?

And can I do an SSS pass with the default SSS material, or do I need that other version of the SSS material that has it broken up into shader parts?

06 June 2006, 03:41 AM
I would try to avoid using clusters like that since they don't really play nice (as far as I know).

As for doing SSS in a pass, I would add overrides for things like Diffuse weight and so on...

06 June 2006, 03:47 AM
Do you know of another way to do what i'm trying to do? Which is use a seperate map for the head, a seperate map for the torso, a seperate map for each limb...

The only way i know of is to use the clusters and apply a material per cluster.

06 June 2006, 03:50 AM
I would avoid the trouble and put the whole head in one sheet, and the body in another.

06 June 2006, 03:52 AM
Are you saying to use a seperate map for the head, and another for the rest of the body?

If so, how?

Doesnt that involve using cluster materials? Isnt that the same thing that i'm doing but with 2 clusters instead of several?

I've done this before as i'm doing it now, it just did not involve SSS. The only work around that i see is to add in the SSS as a pass, where the SSS material is on the entire character on a render pass.

06 June 2006, 04:01 AM
I have not idea how you would go about it...I often use more then one sheet, but it is going to be very painful to do it that way. Even ran into that problem working on an environment model

06 June 2006, 06:28 AM
See if this helps. ;)
Weight Driven Textures (

WMP10 required for this one.

06 June 2006, 06:40 AM

That seems to do the trick but that is quite a bit of work :)

06 June 2006, 06:42 AM

That seems to do the trick but that is quite a bit of work :)

Alot less work than dealing with the problems you're fighting now I assure you. It works quite well and is scalable I assure you...

06 June 2006, 07:01 AM
I'm at the point where i could just map the char with one texture map, but i hate losing resolution like that. I'm not sure i need that much res anyways... right now i'm using like 2K maps for each part.

I could map the char with a single 6k skin which is probably plenty but i tend to want everything hires... why do i do that? hehe

How does this method work with more than 2 ? I can see the mix weight node working with 2, but 3? 4 ? 5? do you start stacking up mix nodes? or do you do it all in a single mix node?

I'm guessing it wouldnt work in a single mix node, and they would need to be stacked?

06 June 2006, 07:04 AM
(I assume you use fast SSS material).

Make sure you connect the same lightmap to lightmap port of your SSS shaders. As far as I remeber, by default XSI will create new lighmap for every new material. I cannot try it now, so bare with me if it does not work.

Well, I did try actually :)

It works for me (

Just make sure you feed the same lmap to the shader.
BTW, I'd not neglect cluster materials so fast, some alternative method might have negative impact on render times.

06 June 2006, 07:07 AM
You can stack them (often the best and most manageable way imho), but it can also be done w/ the Mix8Colors node... you should experiment a bit and see what you come up with. I've pointed the direction and provided a push... you have to walk the path grasshopper. LOL

On most tasks you'll probably find that 2 images will really suffice if you get really efficient with the way you approach the UVing, 3-4 are only occasionally needed when I play. I don't often play with characters myself, but it's all the same when the unwrap is done.

06 June 2006, 07:28 AM

This website seems to suggest the same method but also suggests vertex color and weight map methods as well.

Seems like its best to avoid the cluster materials and go with this method.

Although... it would screw up my 3d painting because of the collapsed uvs. I'd have to have 2 versions of it :) One for 3d painting as i have it now, and one for rendering in xsi.

06 June 2006, 11:36 AM
Funny, I had exactly the same problem with Max amd Multi materials.

In the end I vertex-painted the objects and used that pass as a compositing alpha.

06 June 2006, 12:35 AM
Any idea how to combine this technique with the bump map channel?

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