2/5/02 The Real Story Behind Jim Henson’s Jack and the Beanstalk

Jim Henson’s Jack and the Beanstalk: The Real Story, the recent mini-series from Jim Henson Television, comes to DVD this week (Artisan Home Entertainment, $19.98). The modern retelling of the classic fairy tale starring Matthew Modine and directed by Brian Henson, boasts stunning visual effects from Jim Henson’s Creature Shop. More than 560 digital visual effects shots were achieved, covering the whole gamut of effects and using almost every commercially available 2-D and 3-D package (XSI, Maya, Alfred, Flame, Combustion, Commotion, Illusion and Shake).

Sean Feeney, digital VFX producer for Creature Shop, spoke to AMO about the making of the film:

"The two main CG sequences are Harmonia (fully CG Harp) and the Beanstalk (fully CG growing beanstalk, and practical beanstalk, with CG augmentation, and CG vortex).

"The fabled golden harp was designed as an exquisite carving of a woman, Harmonia, on its frame who comes to life, and who plays the harp she is fused to. Various solutions were discussed, including motion capture of an actress or child, but it was soon decided a digital animation would work better to create the magical effect of life from metal.

"The movement of Harmonia had to be smooth and sensual music, to calm a Giant! A real harpist was first filmed to work out the playing style with the actual score, and an actress chosen to go through Harmonia s moves. The actress was shot from the relevant camera angles to provide a fluid scene and these shots used to guide the animation.

"Harmonia was sculpted at Jim Henson's Creature Shop in London for approval, and then Cyber Scanned; the model was then imported into Softimage XSI, animated, textured, lit and rendered Mental Ray.

"Henson puppeteer Mak Wilson, leading a team of eight animators, led the animation direction.

"The Beanstalk was designed to work in its fairytale setting but to also seem magical in a modern one. Whilst growing, the tendrils had to seem almost alive, searching serpent-like in a burst of growing energy and then to develop into a tough solid mass like a mature vine -- rigid and climbable.

"A horizontal vortex was also designed as an ethereal cut off point for the beanstalk to disappear into, to differentiate the two worlds and to add a real logic to the concept. After all, if a beanstalk genuinely grows through the clouds to infinity, then everybody and not just Jack would see it and want to climb up!

"[In terms of software], it was decided to build and animate the CGI/digital beanstalk in Maya. The beanstalk had to be matched to the camera practical on-set beanstalk whilst also existing in purely CGI environments. With the beanstalk appearing more than 80 shots, growing, stretching, gripping objects, being cut and dissipating into particle clouds, [the] Maya package was chosen as the best solution with particles generated in Houdini.

"Work started on the beanstalk sequence even before the cameras had started rolling. The animation criteria outlined by director Brian Henson was a motion reminiscent of time-lapse photography of plants growing, so we underwent several tests to see what kind of technologies we would require. One of the problems we encountered was with the way geometry would be handled. The look we were aiming for did not allow us to just translate geometry through the ground plane, but rather ‘grow’ it from sapling to fully grown beanstalk, all in the space of a few interlocking cuts. We ended up with a solution within Maya that would allow us to creep geometry up a profile curve, which in turn could be animated by a series of clusters along its length.

"Extensive compositing was undertaken principally so that the Giants were able to interact believably with the humans, tiny in comparison. The sets were built to scale allowing the different action to be composited (combined in layers). Further compositing was necessary to fuse 3-D elements such as the harp and a dragon into the final shots, but also for steam, flying birds, falling petals and dust. Any item that interacted directly between human and giant was easier made digitally, due to the complexities of weight and light effects such as food that is passed between the two.

"The fabled beanstalk, Giants and their kingdom took form through Jim Henson’s Creature Shop’s unique ability to combine digital visual effects with puppetry, animatronics and prosthetics.

"To streamline the animation workflow, we set about unifying all the relevant controls within a scripted panel in Maya. This gave the animators instant access to each of the stalk parameters and tools, allowing them more time to animate, and less time spent fiddling about within the guts of the virtual rig.

"Some storyboards required leaves to unfurl from the growing beanstalk, so we added controls that would allow animators to create constrained instances of leaves on the surface. On creation, their controls would be added dynamically into the interface, giving control over attributes such as growth, unfurl and flap.

"Accurate survey data was collected on set so that we could provide guidance to the director and crew when it came to setting up shots which would later be heavily augmented with CG. Essential tools included the ubiquitous chrome ball light probe, a laser range finder which allowed us to find distances without draping tape all over the busy location, a digital inclinometer to gauge elevations, and a digital camera to capture High Dynamic Range photography of our light probe. Another essential source of information came from continuity, which gave us information on lenses, camera tilts and pans, and corresponding slate numbers, which we could then use to set up our virtual cameras. This information also allowed us to represent the lighting for the shot, and, needless to say, was a huge time saver.

"With the rig set up, and handed over to the animators, work began on the shader. Brian Henson wanted the beanstalk to evolve in texture as it grew, going from a young and fairly translucent sapling, to a rougher, older, more bark like appearance. With this in mind, we decided to tackle the shader procedurally.

"Because of the nature of the sequence, animation was done as one long sequence, with output being piped through multiple cameras. This was then sent to the editor, who would cut together the final sequence with Brian, giving him a lot more control over the timing and pace of the shots.

"Final output also presented a few challenges. In the storyboard, the beanstalk creates a vortex in the sky, through which it can grow. Because this effect was created later in the composite, the interaction of light from the vortex onto the beanstalk would have to be controlled in the composite. Therefore, as well as the usual key beauty pass for the beanstalk, we also supplied the compositors with a normals pass so the compositors could then split the channels and use them to control the lighting effect on the stalk.

"Other passes included several leaf falling passes, height mattes for the beanstalk, individual light passes and specular passes. The idea being that it is easier and quicker to control something in the composite, than it is through a re-render. With heavy procedural shaders like this one, keeping re-renders down to a minimum was a godsend."