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SSS tests

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SSS tests

Post Tue Jun 16, 2009 3:55 pm

I have been working on a reliable way to fake SSS in yafaray here are some tests of what I have so far.

jadetest.png
Jade Standford happy standing Buddha

milktest.png
Milk

skintest.png
Human skin


The jade and milk were made fairly quickly, the skin took a lot of tweaking. They all need more work but esp. the skin.
loh
 
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Re: SSS tests

Post Tue Jun 16, 2009 4:27 pm

Are you using the same approach as the SSS shader in Blender?

Would it be easier to code a "proper" sss shader, e.g. one that does true sss?
ChojinDSL
 
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Re: SSS tests

Post Tue Jun 16, 2009 4:43 pm

Are you using the same approach as the SSS shader in Blender?

I don't know how the SSS shader in blender works, so I can't tell you. But I suspect not. My method requires more than one mesh per object. Until anyone has the time and knowhow to code a shader for yafaray then a trick will be needed.

If anyone knows how I am supposed to demonstrate SSS let me know. I do not know if there is a classic scene for SSS like the cornell box is for GI. Should I show an image will pure backlight or what?
loh
 
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Re: SSS tests

Post Tue Jun 16, 2009 4:51 pm

loh, try with the images on this paper:

http://graphics.ucsd.edu/~henrik/papers/bssrdf/

Nice effect on suzane btw ;) and good luck :D

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DarkTide
 
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Re: SSS tests

Post Tue Jun 16, 2009 7:50 pm

nice man :) that tipe of shader in yafaray or fake mathod is really needed good luck!!!
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STart
 
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Re: SSS tests

Post Wed Jun 17, 2009 9:23 pm

new tests with marble, attempting to simulate the images in paper suggested by Darktide
marbletest2noSSS.png
PM only, no SSS
marbletest2.png
With SSS

model from jotero.com
loh
 
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Re: SSS tests

Post Thu Jun 18, 2009 9:49 am

The results are interesting.
What's your method? Are you duplicating the mesh and play with the translucency value?
Can you post the render times for the last one?
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bupla
 
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Re: SSS tests

Post Thu Jun 18, 2009 4:14 pm

I didn't keep the render times for the images I posted before but here is one rendered at somewhat higher quality, rendered on one half of my core duo laptop (1 thread).
marbletest3.png
marbletest3.2.png


The method is two or three objects, each slightly within the next. The inner meshes were made with shrink/fatten and sometimes the poly reducer script as well as a bit of manual tweaking of stray vertices. (I found that this script made shrink work better besides reducing the unnecessary geometry that is only inside) The outer mesh for each has a translucency of .3-.7. The inner mesh has a somewhat lower translucency. and tended to have more color than the outer one. If there is a third mesh then it tended to be very deformed and much smaller it is usually opaque and either black or white depending on whether I think I need more light reflected out or less.

This could be improved by a script that takes a UV mapped image and produces a BW image based on the distance from one side to the other along the face or vertex normal

If i have the time and there is interest I can write a proper tutorial
loh
 
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Re: SSS tests

Post Mon Jun 22, 2009 5:10 pm

Much Updated skin: now easy to add any type of discoloration such as veins, blush or pimples. The moles were hastily drawn and could look a lot better. The veins are just a sharp marble
skintest062209.png
skintest062209bakclit.png
loh
 
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Re: SSS tests

Post Tue Jun 23, 2009 4:21 pm

loh wrote:Much Updated skin: now easy to add any type of discoloration such as veins, blush or pimples. The moles were hastily drawn and could look a lot better. The veins are just a sharp marble


Very nice!!! :D
Could you share the settings?
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MarcoA
 
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Re: SSS tests

Post Wed Jun 24, 2009 2:31 pm

in render with woman statue near her right arm ending could see that mesh is copied and scaled down have you tried to get rid that? or maybe just I misunderstand that image part?
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STart
 
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Re: SSS tests

Post Wed Jun 24, 2009 5:44 pm

STart wrote:in render with woman statue near her right arm ending could see that mesh is copied and scaled down have you tried to get rid that? or maybe just I misunderstand that image part?


copying and scaling down won't give an equal offset in irregular meshes, so probably is best using Blender script 'solidify selection' which is available if you enter 'edit' mode
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Samo
 
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Re: SSS tests

Post Thu Jun 25, 2009 1:15 am

Interesting results. :)

If the object is a manifold mesh then you could also use alt-S in edit mode to shrink it along vertex normals. This usually gives a decent constant offset, but it can also mess up occasionally.
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wizofboz
 
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Re: SSS tests

Post Thu Jun 25, 2009 4:20 pm

I sometimes use alt-s, shrink, to make the inner mesh, but that seems to have little control. Usually I find that it is better to use sculpt inflate-sub with no fall off on the whole mesh. Samo, I tried the solidify selection and it sort of works but usually something crazy happens like some of the vertices have been moved way outside off the mesh.
loh
 
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Re: SSS tests

Post Fri Sep 10, 2010 6:11 am

Thank you for your idea! But how is it possible do make material some glossy? A tomato, for example.
Glossy tomato
Image
Fake SSS (your method) tomato
Image
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maleficmax
 
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