How does an arachnophobic visual-effects supervisor create an endearing and emotive fully CG spider? Digit found out...

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Bringing a much loved children

Adapted from E B White's charming tale about the unlikely friendship between a barnyard piglet and a spider, Charlotte's Web, directed by Gary Winick, stars Dakota Fanning as Fern and the voices of Julia Roberts, Steve Buscemi, John Cleese, and Oprah Winfrey, among other Hollywood A listers.

Charlotte's Web is the story of Wilbur, the runt of the litter, raised by farmer's daughter Fern and befriended by a barnful of animals and a spider named Charlotte who hatches a plot to saved from him from the slaughterhouse by spinning magical webs.

Bringing it to the big screen required the skills of hundreds of artists, animators and VFX masters from around the world. Stan Winston Studios created a number of animatronic puppets while Rhythm & Hues were called upon to recreate the CG muzzle replacement techniques used in Babe.

Iloura worked on a digital replacement for Wilbur, and Tippett Studio created the rat named Templeton. Charlotte's children were created by Fuel, while the tricky task of bringing the film's second lead animal character the literate arachnid to life was given to Australia s Rising Sun Pictures (RSP).

Creating Charlotte was not an easy ride, recalls RSP visual effects supervisor John Dietz. "Trying to create a photorealistic spider that can also send audience empathy levels though the roof are two briefs that are at complete odds with one another," he says.

Having previously worked at Rhythm & Hues in LA on films such as Babe: Pig in the City and Hollow Man, Dietz left the US to take up the challenge of creating over 200 spider shots at RSP's studio in Adelaide, Australia.

The design process for the character of Charlotte began in August 2004 with RSP's initial pitch, and continued throughout the project, with over 60 artists contributing at peak times.

The film's animation director Eric Leighton and overall visual effects supervisor John Berton Jr joined the RSP team in Adelaide to oversee the progress.

There were numerous challenges with the character, says Dietz. First the team had to take onboard that, as a much loved fictional character, everyone had a preconceived notion of what Charlotte should be like.

This coupled with the fact that real spiders tend to inspire fear and disgust, and lack humanistic feature such as eyes and mouth, made the task of creating a performance that showed Charlotte's character as warm and motherly a major challenge.

Working with several professional spider wranglers, Dietz and his team studied live specimens and then worked with conceptual artists to arrive at a look for Charlotte.

Eye of the spider

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While the look for Charlotte

"It was when we got into the close ups," explains Dietz. "There was still something not feminine enough about her - and the eyes, which are so important for connecting with a character, needed revisions to size and shape."

Working on Charlotte's only potential humanistic feature - the eyes - Dietz and the RSP crew created two main human-looking eyes framed by the remaining six spider eyes positioned along the brow line.

Several revisions later the character was finalized. "It was incredible what a difference it made all of a sudden there she was, and we could get down to the business of putting out shots," says Dietz.

Although the line between Charlotte's head and her fangs appears almost as a mouth line, the character was not designed with an actual mouth.

To add a mouth that just isn t there on a real spider would have instantly removed her credibility, explains Dietz.

"The question was how do we make her talk without a mouth," he recalls. "We came up with the concept that she does have a mouth but it exists behind the chilicerea (fangs).

"So when she talks with that mouth we don t see, there is muscle movement that moves the fangs as a secondary movement. That worked great, but then we had to figure out what that movement was."

The animation of the lip sync had to go through many rounds of improvement until animation supervisor Eric Leighton got the look he was after.

"If she hit every phoneme then it became distracting and too busy, if the movement was too big then they would look like they were sliding on her head. If we opened them up too much she became sort of gap toothed. So working that out took a while," says Dietz.

RSP used Softimage|XSI for modelling, animating and adding fur to Charlotte. " It has some very strong modelling tools and is a strong animation package with its Animation Mixer," says Dietz.

"But the strongest aspect is that they are a very friendly company to work with and make working feel more like a collaboration."

When it came to modelling Charlotte, Dietz divided the spider into individual parts with the torso, legs and eyes being separate objects.

Using a number of 2D images as reference, his team then modelled Charlotte using polygons. Later in the project, the team had access to a 3D scan from a clay model to use as a reference for fitting out the mesh.

Rigging Charlotte for animation posed several challenges recalls Dietz, with most of the team's attention focused on the spider's face. Rising Sun's TDs developed a 'combination sculpting system'.

"The principle behind this system was to use morph targets to create different shapes that represented what would happen if the underlying muscles were to move in a particular direction," explains Dietz.

"We would then sculpt new shapes for situations where combinations of these shapes gave unsatisfactory results. A custom plug-in for Softimage|XSI would then handle the blending of all these shapes at animation time."

Charlotte's main body rig had an underlying bone structure, with a more complex rig on top. Her mesh was then enveloped to nulls that were constrained to the top-level rig.

Each leg consisted of around 20 bones making up seven different chains that were layered to give the animators as much control as possible.

Along came a spider

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Charlotte

"The rig was very flexible and allowed the animators to animate using whatever was most comfortable for them in the given situation," says Dietz.

"The legs, the pedipalps (the secondary pair of appendages near the mouth of a spider), and the eyes could be animated with IK or FK. We managed to animate the entire show with just one rig rather than having to make different rigs to suit different situations."

Alongside the team of animators, 15 lighters and 15 compositors worked on the hundreds of shots featuring Charlotte. RSP rendered the shots using 3Delight - a RenderMan compliant renderer, while lighting was carried out using a custom RSP light rig in Softimage|XSI.

The lighting was completed with an all-in-one beauty shader, then rendered to a list of component passes, says RSP CG supervisor Ben Paschke. This meant that the lighters could see most effects in one test render, but when it came to compositing, the compositors had the flexibility of split-out passes.

"It was important that the lighters could control and light to a shader that was as indicative as possible of the final balance in the render passes," explains Paschke.

RSP compositor Ben Warner says a typical Charlotte build would use 33 passes - 11 passes for the skin, 11 for the fur, six for the eyes, and five for finishing features. "However most shots required additional matte and control passes, so most composites usually had anywhere between 35 to 45 passes and that was just for Charlotte at 2K float resolution," he explains.

"This number of passes meant that we had the ability to control all aspects of Charlotte's look in order to help integrate her into the scan plates as well as push her to meet the director's and VFX supervisor's vision," says Warner.

The compositors could control numerous aspects including separate fur and skin treatments, subsurface contributions, specular intensity and colour, diffuse lighting colour, occlusion control as well as general colour grading and other compositing effects.

"For the most part 3D would nail lighting direction and colour, and the 2D department direction and colour, and the 2D department would push the grades, intensities, and contributions," notes Warner.

The creation of Charlotte and her webs has left Dietz full of praise for his team at RSP. "I'm really proud of the people who made this happen," he says.

"It got really tough yet we all had one common goal whether comper, animator, lighting, supervisor... to make the character of this little spider live up to the expectations of millions of readers around the world, and push the boundaries - not just for what CG can do technically, but what it can achieve emotionally.

"There are projects that are special to be a part of and for me the emotional aspect made it a project and a time of my life that I'm very proud of now and always will be," he adds.

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The eyes have it 
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A huge amount of the Charlotte

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<h2>Pass notes</h2>
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A typical Charlotte build would use 33 passes - 11 passes for the skin, 11 for the fur, six for the eyes, and five for finishing features. "However many shots required additional matte and control passes, so most composites usually had anywhere between 35 - 45 passes and that was just for Charlotte at 2K float resolution," explains RSP compositor Ben Warner.
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For example, when Charlotte ages and gets closer to dying, her webs show age and her lack of agility in their creation. Once the layout of the webs were designed, the biggest issue was how Charlotte would interact with them, and how each web would react dynamically to wind and other external factors.

"It was a chicken and egg scenario," says VFX supervisor John Dietz. "If we animated Charlotte then turned on a simulation, the performance wouldn't always be what the filmmakers wanted.

"If we simulated first, we wouldn't get Charlotte's mass in the simulation and it was impossible to get her feet moving realistically on the Web."

TD Dan Wills solved the problem by writing an entire dynamics system for the webs that dealt with the motion of the web. First, Charlotte was animated on a static web in order to nail the required performance, after which the team turned on the necessary simulation.

They then went back and animated another pass that locked Charlotte to the web. "We did something we called sticky feet, which was the local web movement when she picks up and puts down her feet," says Dietz.

The webs dynamics and lighting were challenging because of the multiple types of draglines made from different proteins in each web. Threads in different areas of the web have different functions and properties.

Dietz explains: "All of these webs behave differently in an environment and with body masses, such as Charlotte climbing around them."

The final look and play of light on the webs was controlled completely in 2D, says compositor Ben Warner. Compositors had a number of noise, control, and specular maps in which a combination of some or all could be brought together.

"The key to webs was the play of light and specular contributions, with regards to the diffuse and web thickness," he explains.

"The breakup and intensity of the speculars allowed the movement of the web to play through the light, and also defines the age of the Web. The cleaner the threads, the newer the Web, but with time and age the webs would become more diffuse, less specular and in many cases less fine and perfect.

"Having the ability to control all these aspects in 2D allowed both artists and supervisors to quickly achieve web looks that were believable, but also 'direct-able' a glint of light highlighting the words in the web at the correct time," he says.

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<b>Project:</b> <i>Charlotte 242 shots (approximately 23 minutes on screen)
Software: 3Delight, Affogato, Boujou, Cinepaint, Flesh, Furnace, Hype, Liquid, Maya, Photoshop,
Softimage XSI, Wings
VFX: Rising Sun Pictures www.rsp.com.au

All images © 2006 Copyright Paramount Pictures - images courtesy of Rising Sun Pictures