View Full Version : fx skin shader questions

03-21-04, 10:56 PM
One of the reasons I bought an fx5700 over a 9600 was because of Nvidia's much hyped "skin shaders" (the other was seeing Mona sax naked with mirrors enabled). I think its supposed to accurately simmulate the way light reflects off of human skin. screenshots of the gfx pixie are what really conviced me.
Does anybody know more about this technology? ATI doesn't have this technology right? Will more games be supporting this in the future?

03-22-04, 02:27 AM
checkthis, http://developer.nvidia.com/object/GPU_Gems_Samples.html
very interesant

03-22-04, 02:29 AM
I thought the skins in Max Payne2 were pixel shader 1.4?

03-22-04, 05:44 AM
You can only enable skin reflections in Max Payne 2 if you have an FX card. If it's only ps1.4 then the option should also be available for radeon cards

03-22-04, 08:19 AM
Skin shading is a complex matter. Humans knows the human face very well. It's a talent we acquire very early and develop to recognize people. Thanks to it, we know extremely well what a normal face can look like and what it can't look like, making realistic skin shaders a delicate thing to get right.

A lot of physical processes happens with light in the skin. Probably the most important is the well-known sub-surface scaterring, which you can compute/display in several ways with pixel shaders. The direct reflections aren't very hard to simulate but they're rather soft, diffuse.

There's no specific hardware technology there, nothing proprietary - that's just shaders. It might seems more natural for nVidia to have implemented a demo with skin-shading first because they have first-hand competencies in house after their acquisition of Exluna. The algorithm they used is basic from a quality POV, but it is very fast. As always, there's still room for improvements however. By comparison, a GPU version of a low-grade motion-picture quality skin shader still takes several seconds to compute one picture.

There are however precomputation techniques which can significantly lowers that time and bring a similar image quality to real-time rendering with sufficient pixel shading computing power (don't expect to run them real-time on a GFX5200).

About the degree of adoption in games, I can't say much - I'm not in games. All I've seen is (very) few games making use of really specific skin shaders (= significantly different from the average material shader), and they were rather conservative. It seems the game people are'nt yet considering we're at the point where their performance is acceptable, which is debatable IMHO... But that's another story, and when it comes to games, they're the ones making the decisions.

Just my 2 cents... :)