Gene S. Lee

Practical experiences with pose space deformation

Pose Space Deformation (PSD) [Lewis et al. 2000] is a shape interpolation technique for animation. This method uses radial basis functions (RBFs) to perform per-vertex, multidimensional scattered-data interpolation. This formulation effectively interpolates a driven shape according to a set of targets, each at a particular driver value. In the case of correcting a pinched elbow, the skinned geometry is the driven, the targets are the sculpted adjustments, and the driver is the elbow joint. This paper presents some practical experience with PSD acquired while creating the film BOLT.

Achieving real-time playback with production rigs

Rig speed is of paramount importance to animation pipelines. Real-time performance provides immediate feedback to artists thereby increasing the number of possible iterations and ultimately leading to higher quality animation. This paper presents a novel method for real-time playback of production rigs inside a host application, such as Maya, without sacrificing functionality or ease of use. Real-time performance is achieved by augmenting the host with Nitro, a replacement strategy for OpenGL drawing events, RigCache, a caching system for minimizing scene graph evaluations, and Parade, a distributed system for scheduling cache updates. Only minimal rig changes are required for the three tools to collectively optimize playback. The result is a seamless experience that is natural, unobtrusive, and preserves familiar work flows.

A hybrid approach to facial rigging

In production environments, facial rigging is commonly done by either geometric deformations or blendshapes. Geometric deformations are driven by simulated muscle actions, which are loosely based upon the dynamics of facial tissue [Magnenat-Thalmann et al. 1988]. Blendshapes interpolate a large number of sculpted shapes [Bergeron and Lachapelle 1985]. The former approach is intuitive, yet slow and less precise. The latter is fast, yet memory intensive and sensitive to model changes. Conventional implementations of both approaches are difficult to generalize in order to build rigs quickly and retarget animation efficiently.

Enhanced dual quaternion skinning for production use

Dual Quaternion Skinning (DQS) is an advanced rigging technique that binds a mesh to skeletal joints. Unlike the popular alternative, Linear Blend Skinning (LBS), DQS avoids the undesirable “candy-wrapper effect” and effectively simulates volume preservation. DQS is a powerful technique, but to get desirable results, it must be extended to meet the needs of production environments, and is therefore not a simple drop-in replacement for LBS.

iBind: smooth indirect binding using segmented thin-layers

This talk introduces iBind, a novel indirect binding technique improving on mean value coordinates (MVC)[1]. iBind smoothly deforms vertices using a control cage by uniquely leveraging heat diffusion on closed, thin layers across a structured set of mean value coordinates. The talk begins by discussing the limitations of previous techniques, and proceeds with an explanation of iBind, which produces fast, stable, and appealing spacial deformation.

Evaluation of the radial basis function space

Radial basis functions (RBFs) are important in computer graphics, with widespread use in reconstruction, animation, etc. In pose space deformation (PSD) [Lewis et al. 2000], RBFs are used to perform shape interpolation for pose-driven deformations. The behavior of an RBF depends on its particular definition. For artists, the relationship between definition and behavior is not intuitive. We suggest a method for artists to better understand RBF behavior through visualization and to evaluate RBF functions according to the requirements of a production environment.

Handling scene constraints for pose-based caching

This paper presents a conservative, uniform method for handling scene constraints, such as look at and parent, in a pose-based caching system. The constraints are organized into a dependency graph where nodes represent the control caches of a rig, and directed arcs link the rigs to specific control caches. For any animation update, the dependency graph indicates which cache to clear and which other rigs to subsequently update. This method supports pre-evaluation, avoids expensive state tracking, and is easy to implement. The result is a seamless experience that works with all types of constraints while preserving real-time performance.

Pixels to parks: new animation techniques for fantasyland

We present the innovative techniques that brought to life an audio-animatronic Lumiere for Disney World’s newest attraction-Enchanted Tales With Belle. Walt Disney Imagineering and Walt Disney Animation Studios collaborated to create a pipeline that was flexible and intuitive for feature film animators. First, motion was digitally choreographed on the computer with a virtual rig. Next, the software detected constraints and motion limitations that would exist on the physical audio-animatronic. This allowed the artist to resolve them and animate physically plausible motions. Finally, the performance was transferred to the audio-animatronic, faithfully recreating the artist-produced motion using motors and machinery.

A deformer-based approach to facial rigging

Facial rigging is the process of adding controls to a face for animating facial expressions. These controls are commonly bound to either deformers or blendshapes, both of which modify the face’s shape, scale, or orientation. Facial rigs created with complex deformers are intuitive, yet commonly slow and less tunable. Facial rigs created with blendshapes are fast, yet memory intensive and sensitive to model changes.

Automated target selection for DrivenShape

DrivenShape is a data-driven deformation that uses pre-computed data (a.k.a. targets) to approximate the effects of a computationally expensive cloth simulation [Kim and Vendrovsky 2008]. Rather than computing a true, accurate solution, DrivenShape produces a quick approximation that satisfies an acceptable margin of error, where error is defined as a difference in appearance or shape.