Indirect lighting through subsurface diffusion

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franz
Posts: 12
Joined: Thu Dec 29, 2011 5:38 pm

Indirect lighting through subsurface diffusion

Postby franz » Sun Sep 13, 2015 12:41 pm

Hi,

Here is a render made with appleseed's upcoming raytraced subsurface scattering implementation:

Image

Image

Direct links to full resolution images:
https://raw.githubusercontent.com/appleseedhq/appleseedhq.github.io/master/img/renders/sss-indirect.png
https://raw.githubusercontent.com/appleseedhq/appleseedhq.github.io/master/img/renders/sss-indirect-mosaic.png

The left room receives all its lighting via diffusion through the translucent object connecting the two rooms.

I would love to see how other renderers (V-Ray, Arnold, RenderMan, Mitsuba, Cycles, LuxRender...) perform in this situation.

The geometry for the scene (in .obj format) is available here:
https://www.dropbox.com/s/vx6nirxape51my4/sss-indirect.zip?dl=0

Franz

Dade
Posts: 206
Joined: Fri Dec 02, 2011 8:00 am

Re: Indirect lighting through subsurface diffusion

Postby Dade » Tue Sep 15, 2015 9:16 am

franz wrote:I would love to see how other renderers (V-Ray, Arnold, RenderMan, Mitsuba, Cycles, LuxRender...) perform in this situation.


I'm going to try to replicate the test with LuxRender (as soon as I find the time). This would give access to few test cases: Path tracing, BiDir, Path+Metropolis, BiDir+Metropolis, Path tracing on GPUs, etc.

LuxRender uses brute force to render volumes: a path can be scattered when traveling inside a volume, if it is, the scattering point becomes a new path vertex (like a new surface hit). How AppleSeed is rendering volumes ?

franz
Posts: 12
Joined: Thu Dec 29, 2011 5:38 pm

Re: Indirect lighting through subsurface diffusion

Postby franz » Tue Sep 15, 2015 11:43 am

Hey Dade, very cool, looking forward to the test.

appleseed doesn't support volume rendering yet. For subsurface scattering, we use the diffusion approximation and have implemented most of the standard diffusion profiles, old and new, with the highest care possible.

toxie
Posts: 118
Joined: Mon Nov 28, 2011 12:30 pm
Location: germany
Contact:

Re: Indirect lighting through subsurface diffusion

Postby toxie » Mon Sep 21, 2015 3:59 pm

Here the scene rendered with iray. Materials do only match so much though, as we couldn't really match the look of your picture.
So material parameters would help tweaking this.
sss-indirect.png
sss-indirect.png (852.29 KiB) Viewed 8911 times
Better you leave here with your head still full of kitty cats and puppy dogs.

franz
Posts: 12
Joined: Thu Dec 29, 2011 5:38 pm

Re: Indirect lighting through subsurface diffusion

Postby franz » Mon Sep 21, 2015 4:25 pm

Hey Carsten,

Very nice! Is this based on the diffusion approximation, or is this volume rendering? If the former, what is the diffusion profile? What was the render time?

Some details about the appleseed render:

I used a Normalized Diffusion profile; pure translucency, no BSDF (I should redo it with a BSDF to get reflections, they look pretty good in your render). The diffuse surface reflectance is set to 0,178,89 (sRGB). The diffuse mean free path is set to 0.6 m. The index of refraction of the sphere is 1.8. The light radiance is 2 W.m^2.sr^-1. The final image is converted to sRGB.

Franz

toxie
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Joined: Mon Nov 28, 2011 12:30 pm
Location: germany
Contact:

Re: Indirect lighting through subsurface diffusion

Postby toxie » Mon Sep 21, 2015 5:10 pm

Ah, that will help a lot.. Will post another one with these settings tomorrow i guess..

And its brute force volume rendering, not even using the advanced samplers. Rendertime was around ~10mins i think.
Better you leave here with your head still full of kitty cats and puppy dogs.

toxie
Posts: 118
Joined: Mon Nov 28, 2011 12:30 pm
Location: germany
Contact:

Re: Indirect lighting through subsurface diffusion

Postby toxie » Mon Sep 21, 2015 5:24 pm

sss-indirect2.png
sss-indirect2.png (1.02 MiB) Viewed 8890 times

that matches better.. :)
Better you leave here with your head still full of kitty cats and puppy dogs.

franz
Posts: 12
Joined: Thu Dec 29, 2011 5:38 pm

Re: Indirect lighting through subsurface diffusion

Postby franz » Tue Sep 22, 2015 8:34 am

Very nice. Is that GPU or CPU rendering?

I did another render with the addition of a reflection component, just for fun...

The sphere is probably better treated as an actual volume rather than a diffuse translucent approximation, given how big the mean free path is... By the way, do you have diffuse approximations to translucency in Iray?

Franz
Attachments
sss-indirect2-emeraude.png
sss-indirect2-emeraude.png (390.97 KiB) Viewed 8772 times

beason
Posts: 47
Joined: Sat Dec 10, 2011 1:58 am
Location: Los Angeles, CA

Re: Indirect lighting through subsurface diffusion

Postby beason » Fri Sep 25, 2015 4:00 am

Cool! Looks good, franz and toxie.

rouncer
Posts: 18
Joined: Wed Jun 19, 2013 11:04 am

Re: Indirect lighting through subsurface diffusion

Postby rouncer » Tue Feb 02, 2016 3:04 pm

god everyones renders look so sterilized like a hospital!
max resolution + simplified scene.

Surface scratches and some more light sources would definitely help the issue a bit.


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