What does Sub Surface Scattering do - Graphics Settings Explained

Written by Jon Sutton on Sat, Sep 28, 2019 4:00 PM
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Sub Surface Scattering (SSS), sometimes known as Subsurface Light Transport, is a method for simulating light passing through objects and generally affects skin. The name quite literally means light scattering from the point beneath a surface.

The focus of Subsurface Scattering is one what we’d typically deem partially translucent objects, which is why it most obviously affects the quality of characters’ skin and eyes. This feature isn’t exclusive to skin though, as it can also add substance to other partially translucent objects in games, including paper, wax, and hair. However, SSS is still used almost exclusively for skin in video games these days, particularly as we find alternate methods of lighting.

Below we have an example of human skin without subsurface scattering (left) and with subsurface scattering (right). As you’ll see, the inclusion of a complex bump map for the skin necessitates SSS in order to more authentically represent the appearance of real skin. Play a game from around 2007-2010 and you’ll see plenty of examples of characters looking like the left-hand picture.


As for how this manifests in-game, the prominence of the effect can vary. You’re going to most notice this effect during in-engine cut-scenes when the camera’s up close to a character. However, during general gameplay the effect will be fairly minor, although certainly more noticeable in first-person titles.

How demanding is Sub Surface Scattering?

Subsurface Scattering isn’t very resource intensive at all and typically only has a minor impact on the GPU. During typical benchmarks we found SSS affected frame rates in the region of 0-2%, meaning its performance impact is negligible. You will typically find Sub Surface Scattering just has an On and Off toggle rather than any more granular choices.

Is it worth enabling Sub Surface Scattering?

Due to Sub Surface Scattering having little to no impact on gaming frame rates we would recommend you enable this graphics setting at all times. In particular, first-person games can benefit a lot more from Subsurface Scattering. The effect will often apply to your character’s arms, as well as when you get up close to NPCs. Disabling SSS should be a last resort for performance-related issues.

More Graphics Options Guides

Ambient Occlusion

Anisotropic Filtering / Texture Filtering

Decals / Decal Filtering

Sub Surface Scattering

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10:13 Sep-30-2019

SSS in games is, naturally, a hack. Calculating real SSS in terms of a raytracer requires a good chunk more computation time, which is not at all reflected in the hacky SSS in games (especially in the sample above where the diffuse channel seems to get a bit of blur to fake appearance). There are more advanced ways of doing it with translucency maps which provide a more realistic result at the expense of rendering time, of course.

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10:16 Sep-30-2019

I'd say a better example of SSS in the real world would be the way our hands and ears look when obscuring a strong light. (those are CG examples, but you can try this at home. If you have a strong-enough light, like a powerful LED - you CAN actually see the skeletal structure in your hand! I've tried it...)

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12:14 Sep-29-2019

Smoothness of the skin, especially the cheeks, is definitely noticeable and more realistic from my point of view. I think this little thing can add up to realism with many other details coming in the future.

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06:13 Sep-29-2019

im a bit conflicted on this since the left picture is a more real representation of human skin when looking at it close up in a mirror. But the right imagine with SSS produces a more photo finish in thats what your face looks like on a camera even when you zoom in you wont make out all the complexion details.

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06:16 Sep-29-2019

This does depend on lighting,exposure and sharpening in a scene but i guess if you want games to look more movie like SSS does that for you. Or turn it off for a more gritty look since really the only difference will be seen in closeups/zoomins like dialogue sequences in games.

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01:13 Sep-29-2019

looks worse

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01:11 Sep-29-2019

no its not worth it

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20:01 Sep-28-2019

all i see is more shadows at the left eye

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20:40 Sep-28-2019

I missed that. XD
And this is a static picture, we won't be able to tell a real difference in motion :D

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21:13 Sep-28-2019

There is much more to see, for example in mouth, when it is off, it is more darker. Or in the nose...

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16:41 Sep-28-2019

if you did not write on / off i could not tell which is which

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16:45 Sep-28-2019

the difference is the mouth, that's all I can see. The lips and the tongue... and that's a static picture, imagine a 30-60-120-240fps motion.

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16:30 Sep-28-2019

If it's only a 2% performance hit then sure, even though I can barely see a difference, close to none, unless someone is trying to squeeze out the maximum amount of FPS.

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11:09 Sep-30-2019

Yeah very minor differences although fortunately barely any performance hit

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