Friday, May 9, 2008

Subsurface Scattering II

Yesterday we took a look at the way light enters the skin and scatters below the surface, creating an unmistakable glow.

Sculptors who create hyper-real figures know that in order to fool the eye, the surface layer of skin has to be somewhat translucent. That’s why the figures in wax museums look more real than painted plaster. Your eye instantly spots the difference.

This was always a problem for Duane Hanson’s (1925-1996) figures, which were made from cast fiberglass and polyester resin. They were realistic in every other way, but the skin often had an unnatural opacity.

In the earlier days of movie animatronics, such as “Gremlins,” above, the skin was made of cast latex, which was a little too opaque, but now visual effects wizards generally use silicone when they need the surface to transmit and scatter more light.

Thomas Kueblers amazingly lifelike figures are made with a secret process using silicone. Note the subsurface scattering at the edge of shadow along the nose.

Ron Mueck, who makes realistic larger-than-life figures, uses silicone for babies, whose skin scatters light even more readily than adult skin.

The field of 3D animation and digital effects is developing the theory behind subsurface scattering. In the early Toy Story and Shrek films, it wasn’t possible to convey the effect, but now it has become a standard practice, and was used effectively in "Lord of the Rings."

Here are two images by Henrik Jensen, the first without subsurface light transport.

To get it right, computers have to be taught to consider density variations, form thickness, and light direction. Artists in the 3D animation field often get plenty of credit, but here we have to pay our grateful respect to the mathematicians, scientists, and programmers.

This is one of the reasons I’m glad to be a painter right now, and not in some past age. There’s a cross-fertilization of knowledge and technique happening between all these fields of art and science.
Ron Mueck, link.
Thomas Kuebler, link.
Gremlins copyright Amblin Entertainment, link
Gollum copyright New line Cinema, link
CGI examples by pioneer Henrik Jenson (Thanks, Mr. Atrocity), link


Tom said...

Just to take an opposite track James, and not trying to be a trouble maker, where is the art in these sculptures, they seem to take the mind down to the level of revulsion, like looking at the details of a wound or watching a medical operations fascinating and disgusting. Restraint and simplicity always seem to strike a greater internal chord. A Greek or medieval sculpture seems to have infinitely more power, for all there lack of realism.

They are great for movies but I don't know if I would want them for a public space.

James Gurney said...

Tom, you raise a fair point, but of course it's not the one I was addressing in the post. I was just looking at how these guys achieve verisimilitude.

I haven't seen Mr. Mueck's work in person, but have seen a couple Hansons and Kueblers, and find them quite striking and interesting, but at the same time almost embarrassing to look at, because you know you're not supposed to stare. I think Kuebler's work is brilliant because of the caricature and storytelling. Don't know if I'd want one in my house, though.

But your point is completely valid, and a good one for discussion. Realism is just one objective in art, and it's not the only one or the ultimate one in itself. Like you, I love Greek sculptures for their simplicity and idealism. It's hard to believe when you look at the white marble statues that the Greeks often painted them in polychrome.

Shane White said...

Posts like this make me realize that I only know a small portion of what I'm really seeing. My focus is on so many other parts of making a good picture that I'm not sure how much more 'seeing' I can do.

I guess when your painting in the studio, every little bit counts. When you're painting from life, you're at the mercy sometimes of the failing light.

I'm sure once you get it into your bones it becomes second watching for tangents, avoiding tension between shapes, etc.

The science of art, while fascinating seems equally overwhelming at times. Thanks, regardless.

I guess to suspend disbelief every little bit helps. :)


Victor said...

Uncanny valley, anyone?

I think some of the examples you wrote about in your post seem less realistic and rather unsettling in their efforts to achieve realism because they sort of overstate that last 1% is needed to create the impression of human skin. It's sort of like when a portrait painting's edges are overstated; better leave things to the imagination than accidentally over-doing it.

JP said...

One of my favorite examples of this principle is evident in the character Davy Jones from the Pirates of the Caribbean films. I was shocked to find that although they used lots of reference for the character, he was an entirely digital creation.

An argument can be that Jones is not humanoid enough to approach the uncanny valley effect, but I was certainly sure, sitting there in the theater, that there was an actor hidden behind a digital and prosthetic mask. The uncanny valley effect was avoided with Jones, especially in the eyes, by using the actor's real eyes as a reference point. Once again, as I have found with all my favorite artists, good use of reference from life makes all the difference.

Super Villain said...

i think the art works posted are absolutly phenomenal, especially the work of Thomas Kuebler. thanks so much for posting his work and the link to his site.

always wonderful to find a new artist producing somthing unique and really well crafted.

i noticed he will be showing work at IlluXcon, Altoona, PA, in late november. do you plan showing any orginal dinotopia paintings? if your going to be there i'll get tickets....hope you can make it!

thanks again for the link!

James Gurney said...

The Mona Lisa of the Uncanny Valley is Pixar's 1988 "Tin Toy"

Super Wu: I'm afraid I'll be traveling during IlluxCon, so sorry to miss seeing you and the other attendees.

Shane, I know exactly what you mean about being overwhelmed with all the things to think about when you're painting. I forget all the theory when I pick up the paintbrush, and feel like I'm entering a dark forest.

John-Paul...Yes, loved that Davy Jones!

Richard said...

I'd love to know how to actually apply the paint(s) to make skin appear to have subsurface scattering. Surely red in certain areas will suggest it (David's "The death" of Socrates in the Met has a red belly button) but the side by side face doesn't depend on change in hue as far as I can see. There is more gradual transitions between values like in the highlight on the nose, but I can extract from it a method or theory. By the way what about blue veins that often appear in young women.


Tom said...

think the Greeks my have use glass in the eye sockets of some of their bronze sculptures. The clearness in some of the eyes was incredible especially in Thomas Kuebler's work. My post was sort of just a gut response to the work and it did not have anything to do with what you where explaining about light and its relation too form. You always give me something new too see and consider in my art work, in others art work and in nature and I appreciate it.

Clayton J. Beck III said...

James, your blog is a wonderful oasis in the desert of art instruction and encouragement on the web.

I've never heard the term Subsurface Scattering for the effect you are describing. The description you have for it is very good and I believe clear enough for most to understand. The idea of light transmitted through semitransparent layers and then re-emitted out the other side can be rather complicated but you've explained it very well.

In oil painting Anders Zorn did it quite often by placing his models near a window than allowing the light to pass through the ear. He would often accomplish this with one accurately placed deft brushstroke. Nothing quite like the look of pure cadmium red stroke in the middle of all that gray-brown stuff.

Sargent, Sorolla and Schmid all liked it also. Sargent like to do it opaquely, Schmid would do it more with transparency, and Sorolla would use a combination of anything that worked. My friends Dan and Scott like to do it also by placing a spotlight behind their model's head and allowing the light to pass through projecting forms like ears and noses. It's a lot of fun, but just a parlor trick, BUT IT'S A LOT OF FUN!


James Gurney said... Beasts of Neptune art on your blog. Also, I grew up near Alum Rock Park!

Richard, fascinating stuff about facial recognition on your blog. About where to see subsurface scattering: the best place is to see it is along the shadow edge in a small backlit form. It also shows up in the light side in the reddening of hollows (like belly buttons or nostrils).

Thanks, Tom and Victor; I'm really glad you brought up the point about the uncanny valley. It was a big topic of discussion around here all day. The "Polar Express" movie was another example that came to mind.

And Clayton, thanks for the insights on the Zorn etc. Your paintings are spectacular, and it's generous of you to share wisdom from the Palette & Chisel and the American Academy tradition.

Sarah Stevenson said...

Fascinating. I really like Duane Hanson's work--definitely makes the viewer a little uncomfortable. I don't think I've ever seen anything by Kuebler, though--great stuff.