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Vue F.A.Q (Last Updated: 2024 Nov 21 4:12 am)



Subject: Fake Subsurface Skin Scattering in Vue


dburdick ( ) posted Mon, 23 May 2005 at 8:27 PM · edited Mon, 25 November 2024 at 1:33 PM

file_243358.jpg

I think I've come up with a simple way to fake subsurface scattering in Vue. It's similar to the procedure that FaceOff uses in Poser except that the reddening of the skin texture is tied to the angle of incidence of the camera versus the main light. This works reasonable well when the camera and main light source direction are roughly pointing in the same direction. Basically, what you do is take an Angle of Incidence input node and tie it to a color map tha ramps from all black (high angle of incidence - perpendicular) to slightly red (low angle of incidence - parallel). I put a map node in between just to play with the ramping effect and then tied it to my main texture with color combiner ADD function. It's not perfect, but it's a start.


Dale B ( ) posted Mon, 23 May 2005 at 8:56 PM

Definitely a start! Bravo! Now if a way for the light transmission can be found, so that things like ear shells have that glow, this could be applied to just about anything in Infinite (like possibly the plant leaves. That would be incredible....assuming it didn't kill the render time)


sittingblue ( ) posted Mon, 23 May 2005 at 9:29 PM

You have some brilliant ideas. I'm fascinated.

Charles


dlk30341 ( ) posted Tue, 24 May 2005 at 11:02 AM

BRAVO!!!!


bruno021 ( ) posted Tue, 24 May 2005 at 12:51 PM

That's interesting, but subsurface scattering is not about the skin getting redder, it's about light going through the thin layers of skin, hence the reddish effect, but this won't work for hair, leaves or ice. And also, this effect only happens when the skin gets in contact with a strong sun ray or lamp. I think that the "distance on ray" node might prove useful in this, but I really don't know how. How about you give it a try? I'm sure it's there somewhere, and that you or another SSS maniac will come up with the right shader. And we'll all be thankful.



dburdick ( ) posted Tue, 24 May 2005 at 11:03 PM

Re: bruno021 As I understand the SSS effect as implemented by FaceOff and others, as the object polygon becomes more parallel to the main light source, the polygon should be tinted more red (e.g. more red in the shadows). Am I missing something here?


Dale B ( ) posted Wed, 25 May 2005 at 6:31 AM

Bruno is talking about -real- SSS; what you are doing is indeed a variant of what Face Off is doing, which was faking the effect in controlled environments in an application that didn't know SSS from Adam. True SSS in Infinite would be applicable to leaves, flowering plants, basically any solid that has a tranlucent, or multiple translucent, surfaces. It may be possible to build a shader that emulates true SSS....or E-on may have to build on into a future build of Infinite, as the did in P6. What the time penalties for true SSS would be in an Infinite scene I have no idea....but it probably wouldn't be cheap...


svdl ( ) posted Wed, 25 May 2005 at 10:55 AM

True SSS is possible in Vue: you'll need a clone of the object scaled slightly smaller (probably some other adjustments too) contained within the original model. The original model should get a slightly transparent material, maybe some volumetrics too, the contained model a reflective material. Haven't played with it yet. I can make a slightly smaller clone in a modeling program (in Max I'd use the Push modifier for half a millimeter). For totally realistic SSS you'd need several clones, each contained within the other. Rather heavy on polygons, and the texturing is a bear. Fake SSS like in Poser 6 or the face_off shader is physically inaccurate, but renders much faster and requires much less setup.

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bruno021 ( ) posted Wed, 25 May 2005 at 11:16 AM

svdl, this would be a workaround too, not real SSS, but that would be nice to see what you come up with this technique. Doubling or tripling the model will certainly take longer to render, but then maybe one or more of these models could be low-poly. Still, I think the distance on ray node might be the answer, combined to some filtre, wish I had more time to play around with it.



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