Issue: Volume: 26 Issue: 9 (September 2003)

Labor of Love

By Karen Moltenbrey

There are times when our perception of reality becomes "more real" to us than reality itself. This was the contradiction confronting the digital artists at The Mill when they created a computer-generated fetus to star in an all-CG television commercial for the German building society Badenia. To illustrate the point that Badenia will protect and care for its customers during their lifetime, just as their mothers cared for them in the womb, director Bernd Muller instructed the artists to generate a photorealistic, near-full-term fetus inside its mother's womb. But when the artists began looking at medical and scientific references, they discovered that an actual fetus at this stage of development didn't match their conception of what it should look like. Rather, they envisioned something that more closely resembled a one-month-old baby.

"We found that a fetus at this gestation is very skinny and has translucent skin, so the veins are very prominent," says Rob van den Bragt, lead 3D artist. "We wanted a baby that was aesthetically appealing; one that was more of an idealized version. We tried to copy reality as much as we could, but we kept an eye on the artistic side as well."

Like real expectant parents, the artists at the London studio contemplated questions such as, What temperament will the baby have? What is he or she thinking? What does the baby look like? Unlike other parents, though, artists Thomas Pastor and Yann Mabille could control the genetics of their virtual child.

Not only would the 3D character have to be approved by the client, but it would also have to meet the expectations of the project team. "The difficulty was modeling a baby that everyone thought looked cute and, more important, real," says van den Bragt, who assumed the role of surrogate father by overseeing the creation process.

Using Maya and Softimage|XSI, artists at The Mill created an idealized model of a fetus inside its mother's womb. The model (inset) consisted of 21,000 polygons prior to the application of subdivision surfaces. Camera-projected 2D photographic texture

To model the baby, the group used both Alias Systems' Maya and Softimage's XSI—a decision that made the team a little uneasy at first. "We created a good portion of the model in XSI, then imported it into Maya for the UV layout. After that, we brought it back to XSI for final adjustments and texturing, before exporting it once again to Maya for animation and rendering," explains van den Bragt. "Anytime you switch back and forth between two competing programs like we did, you never know if they will interact well. However, we had a tight deadline, so we decided to use the tools that the artists were most familiar with, and in the end, [the two programs] worked well together."

While the model itself was not very large—21,000 polygons prior to the artists applying subdivision surfaces—the final version was fairly robust at 20mb. "We added as much detail to the textures as we could," says van den Bragt. "If you look at the lips, for instance, you can see the little section of skin that surrounds them."

The team's goal was to create a conceptual yet nearly photorealistic character. They did this by applying several layered shaders with high-res textures (top) to a finely meshed 3D surface (middle). To give the fetus realistic movements, the artists b

To achieve the desired level of realism in the model, the group intended to use only camera-projected 2D photographic surfaces, whereby artists "project" a photographic texture from a subject onto the 3D model, matching up specific points. Then, they push, pull, and stretch the texture until it fits properly over the corresponding geometry of the 3D model. For this project, the source of these realistic textures was flame artist Andrew Wood's newborn infant, who was photographed from head to toe, providing the artists with authentic skin pigmentation and coloring for their CG baby. This natural texture, prepared in Adobe Systems' Photoshop, was augmented with a procedural surface van den Bragt had generated within Mental Images' Mental Ray, embedded within Maya. "The textures from the real baby gave the procedural texture more refinement and the randomness necessary to achieve a realistic look," he notes.

The use of camera-projected textures, however, created a snag in the workflow as the artists toggled between Softimage|XSI, which they used for the majority of the texturing, and Maya. This glitch was caused by the differences in the way each software program processes these camera-mapped surfaces, resulting in an incompatibility issue whereby "you lose some quality in your textures with Maya," says van den Bragt. "Unlike XSI, [Maya] won't allow you to split a model, freeze the UVs from the projections, and then put the model back together into its original pose." To overcome this issue, the group baked the textures onto the model in XSI, which allowed them to transfer the textures directly onto the Maya baby model with matching UV coordinates.

At first glance, the stylized virtual fetus is often mistaken for the real thing—until the animation "kicks in." That's because the script called for the baby to move in such a way that would be unnatural for a near-newborn. In the commercial, an outside noise momentarily awakens the fetus from a comfortable sleep, prompting it to subtly knock on the wall of the womb, indicating its desire for quiet. The sounds cease, and the baby smiles and goes back to sleep.

"We had to make this illusion look real, which we did by creating slight movements so they seemed appropriate," says van den Bragt. "The client wanted to make sure the action was obvious, but if we went too far with our animation, it would destroy the whole look of the commercial."

The key to pulling this off was to create an extensive bone structure for the character, which was set up within Maya by animator Koji Morihiro. "[The baby] has one of the more complex riggings I've seen, enabling us to achieve subtle but effective hand movements," states van den Bragt. In fact, the team tried to closely match the joints and bone structure of its digital model with that of an actual human skeleton, "so every joint rotates at the right location," he adds. "We wanted to build the model properly so if we moved one of the arms, then the subsequent wrist, shoulder, and head motions would be correct." In all, the character skeleton contains 450 bones, compared to an actual human baby skeleton, which has approximately 300.

The character's highly advanced character rig utilized a complex forward/inverse kinematics setup, hundreds of skin clusters, and numerous morph targets for achieving complicated deformations and motion. Yet, the character rigging was user-friendly, thanks to the use of control sliders and so-called puppets, or clustered sliders that reproduce a complex motion involving a specific area of the body, such as the wrist. "The baby's movement is understated but extremely detailed," notes van den Bragt. "You can even see a little flicker of the eye under the closed lid and little twitches near the corner of the mouth." The team also created a script that incorporated some camera noise, giving the animation the appearance that it was captured with a handheld camera. "We added as much randomness and imperfection as we could to make the spot look imperfect yet perfect."

The lighting, like the baby model, also appears plausible, even though it, too, is not based on reality. Medical images of real fetuses are usually acquired with a fiber-optic camera and are front-lit, making the overall image shiny and flat—"not very appealing," van den Bragt points out. The Mill's baby, on the other hand, was back-lit in Maya and bathed in warm yellows, oranges, and reds to lend a film-like quality to the imagery. "The shadows and lights contrast nicely for an artistic, rather than realistic look," van den Bragt comments.

To achieve a soft, warm look for the imagery, the artists back-lit the model in Maya, and added an overall orange tone, achieved through a shader that gave the lighting a subsurface scattering-like effect.

The team accomplished this look through a shader that van den Bragt scripted in Maya, which made the light appear as if it were under the skin, similar to a subsurface scattering effect. "Subsurface scattering isn't available in Maya, so I came up with a cheat using depth-map shadowing instead of raytracing for shadow casting," he explains. By using depth maps, the group achieved a soft, "almost innocent," look, which raytracing typically doesn't provide.

Once the modeling, animation, and lighting was completed, the group rendered the imagery using an 80-unit dual-processor Linux-based rendering farm running Mental Ray for Maya, making the project one of the first TV commercials to use this release of Mental Ray. With the availability of the Maya-based rendering software, The Mill, originally a Softimage-only house, was able to use its pre-existing rendering pipeline, which, until now, was only available to the company's Softimage users. "The rendering quality Mental Ray offered was exactly what this project needed," maintains van den Bragt, "and with Mental Ray for Maya, we didn't have to sacrifice the knowledge and experience we had with the advanced Maya shading and character tools."

All the imagery was composited within Discreet's flame by Justin Bromley. He also enhanced the glow surrounding the baby and the velvety peach-fur layer to the baby's skin, added rim lighting, and gave it a soft focus, all of which provided depth and contrast to the model.

"Many times when digital artists try to simulate humans, they focus on what makes the person look real rather than on what makes the picture look good," explains van den Bragt. "We tried to walk the line between the two."

The project, which took about 10 weeks, was a labor of love for the team, particularly for van den Bragt, who grew attached to the CG baby. "Early in the process, we rendered out the first shot to show to the client, and the image had a soft, hypnotic look. It looked like a real baby at that point, or what you would imagine an actual baby to look like," he says. "I worked with that shot for a month and a half, and I couldn't stop looking at it. It just didn't look like your typical CG character."

Karen Moltenbrey is a senior technical editor at Computer Graphics World.

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