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Large scale fabric

Posted: Fri Feb 13, 2015 8:38 pm
by itai bachar
Hey guys
Im preparing for a job I might get, it needs big fabrics falling from the sky, silky, transparent-ish style,
the general look is something like Cristo's art:
Image
Ive started testing with maxwell, I started with a Satin shader,
and inserted a fabric texture map into the transmittance of the base layer, attenuation 0.5 mm, & thin SSS.
It looks nice as a start, but the texture is a bit too harsh and of course there's no detail yet (fabric seams, edge etc)
What do you think? any tips?
thanks
itai
Image
Image

Re: Large scale fabric

Posted: Sun Feb 15, 2015 10:38 am
by seghier
are you tried with opacity of the object ?

Re: Large scale fabric

Posted: Wed Feb 18, 2015 6:47 pm
by eric nixon
If you use opacity, It will look strange and render 2x slower (each ray needs to be calculated twice).

I have a tip which you may not be aware of; In mw3 you can build the material with two layers, the first layer contains the thin-sss bsdf/s, then a second additive layer contains the specular and diffuse bsdf/s.

Its also a good idea to just use transmittance in the thin-sss, so the R0 is black and just use grey (of any intensity) in the R90. If you put colour into r0/r90 you will get the inverse of that colour in the rendered transmission. so dont do that.. Also keep the thin-sss roughness fairly low to get the most transmission.

Image

Thin-sss is a bit of a cheat, it doesnt offer the physical realism of a regular material, and some surfaces such as a rubber balloon I have never been able to render convincingly, but if you tweak it by eye you can get decent results. I have had success with paper, plastic, some fabrics, grass and leaves....

One final thought is that thin-sss fails when there are multiple layers, such as a stack of papers, the light travels through the first two pieces of paper but hardly gets any further.

I live in hope that we get a better version of thin-sss one day, or at least the ability to weight the bsdf according to viewing angle, in order to get a more convincing result at acute angles.

Re: Large scale fabric

Posted: Thu Feb 19, 2015 5:40 pm
by itai bachar
Thanks Eric!