The Light from Down Below

When we hold our hand against the sun, it looks red along the edges, because light enters our skin. The appearance of an object is strongly influenced by scattering of light inside the material. "It is called subsurface scattering", says Christian Freude, who works on the new rendering method together with Károly Zsolnai, Thomas Auzinger and Michael Wimmer. "This scattering inside the object is the main reason why different surfaces can look so different. Skin does not look like wax and a plant does not look like a stone surface", says Christian Freude.

Skin is particularly tricky. A face can be rendered in high resolution, with ultra-realistic details, down to single pores and tiny impurities; but this does not mean that it looks realistic. When subsurface scattering is not taken into account, even a perfectly modelled face looks as if it has been chiselled out of a dull, opaque, skin-coloured stone.

It's About Computing Time

"In principle, we could simulate the physics of light scattering below the surface", says Christian Freude. "But to do that, we would have to simulate countless light rays, and it would take hours to render a single picture." Therefore, the research team looked for a method to achieve a similar effect in fractions of a second. This is how the "SSSS-method" (separable subsurface scattering) was developed.

Jorge Jimenez from Activision-Blizzard came up with the basic idea and went on to develop a similar method especially for skin. "Based on that, we have worked out the mathematical basis for displaying arbitrary materials, for example marble, wax or plants", says Professor Michael Wimmer.

"We start by calculating the scattering of a single beam of light below the surface. With this result we can create a simple filter profile, which can then be applied to the images again and again", says Christian Freude. "The computer image is still created with conventional methods, then we modify it with our SSSS-technique, improving the appearance of the surfaces."

"We sought an elegant solution that can be applied to a picture that has already been rendered. The final version of our method only takes half a millisecond per image in full-HD-resolution, on standard commodity hardware", says Károly Zsolnai. This means that the smoothness of the motion is not affected.

"Attempts to include subsurface scattering in real-time rendering have been made before, but up until now, the computing time has always been too long for practical purposes", says Christian Freude. "We have now been able to reduce the modification of a two dimensional image to two one dimensional calculations. This saves computing time but still yields very convincing results."

"This reduction of the dimensionality has been achieved using various mathematical methods, ranging from exact integration and numerical optimization to user-driven color profile modelling", says Thomas Auzinger.

Activision-Blizzard is already using this method. The team is confident that the SSSS-method will soon be used in many other applications too. The new method will be presented in the journal "Computer Graphics Forum", so all developers will be free to use the new approach.

Read more at: http://phys.org/news/2015-05-methods-realistic-surface-games.html#jCp

I never like seeing these types of photos. Unless these things can be rendered in a full game environment. Where processing power is reduced. It won't look like this yet. GTA V is a great example. It's enviroment system is beautiful. But if you look at everything closely. Most of the stuff has low poly models. A lot of stuff isn't smooth.

Well, most games don't really need everything looking spectacular. How many people are going to complain that, if you move the camera close to a wall on GTA, the textures are low res? Its better to concentrate on other aspects than in craft even the last skin and wall.

IMO, the more graphics technology advances, it just makes humans look creepier and creepier.

Maybe its me, but looking at the video I kind of always liked the models lableled as without subsurface scattering better than the others...they're sharper and sometimes look more real to me. The ones with subsurface scattering or the new method applied seem eerily smoothed out and plastic, which is exactly what it was meant to prevent?
Maybe I'm getting it wrong?

Bloodborne is actually close to that, game has a lot of tesselation and high quality textures

I'm not sure about GTAV but for me personally, it was, and still is, the most believable world ever created in a game bar none. Even now, after finishing the game on 360, and finishing it again on PS4 I'm still finding places I know I've never been to before and I don't have any problem with thinking anything I look at looks unnatural. 99% of that game is totally believable in terms of assets.

I actually didn't mean closely with the camera up close. Take Frank's tank top shirts. Nothing is smooth. You can see the polygon flat edges, pretty clearly. But the issue lies with something is gonna look bad to do that type of rendering job on the character. Main player looks great. Enviroments look poor. Vis versa.

Cool! Can't wait till games start using these things

Jorge Jimenez is iryoku, the guy that developed MLAA and SMAA, so he knows what he is doing.

http://www.iryoku.com/