Disney Enterprises, Inc.

University of California

Joseph M Teran

Andrew Selle

Alexey Stomakhin

Eftychios Sifakis

Aleka McAdams

Rasmus Tamstorf

Chenfanfu Jiang

Kelly Ward

Theodore F Gast

Lawrence Chai

At least some embodiments of the present disclosure relate to a method of visualizing objects having frictional contact. The method includes transferring masses and momentums of a plurality of particles of an object to a grid including a plurality of grid nodes; updating momentums of the grid nodes based on the transferred masses and momentums of the particles; transferring the updated momentums of the grid nodes to the particles of the object; updating positions of the particles and deformation gradients of the particles based on the updated momentums of the grid nodes; projecting the deformation gradients for plasticity of the object; updating elastic components and plastic components of the object; and outputting a visualization of the object based on the positions of the particles of the object.

Computerized rendering of objects having anisotropic elastoplasticity for codimensional frictional contact

The disclosure provides an approach for reducing information loss when transferring from particles to grid and vice versa in a hybrid Lagrangian/Eulerian simulation, while also preserving stability. In one aspect, referred to as the rigid particle-in-cell (RPIC) method, a simulation application stores a sampling of local angular momentum for each particle, helping to preserve the angular momentum that would otherwise be lost in the transfer from grid to particles. In another aspect that is more generally applicable and referred to herein as the rigid and shearing particle-in-cell (RSPIC) method, the simulation application stores, for each particle, a matrix with rotational and shearing information. The RSPIC method effectively reduces dissipation, preserves angular momentum exactly, and prevents instabilities. Further, the RSPIC method is applicable to both incompressible liquids and material point method (MPM) simulations of materials such as solids.

Particle-in-cell methods preserving shearing and rotation

The disclosure provides an approach for simulating and rendering materials across different states and undergoing phase transitions. In one configuration, a simulation application generates video frames depicting a material phenomenon using an augmented material point method (MPM). Traditional MPM does not handle incompressible materials such as fluids. Techniques disclosed herein augment the MPM with a Chorin-style projection technique to enable simulation of arbitrarily incompressible materials. In one configuration, this is achieved with a marker-and-cell (MAC) grid based MPM solver, a splitting of stress used in the simulation into elastic and dilational parts, a projection-like implicit treatment of the Eulerian evolution of the dilational part of the stress, and particular techniques for rasterizing and updating quantities on the MAC grid. In addition, a heat model may be coupled to the MPM solver, allowing material changes to be driven with temperature and phase changes.

Augmented material point method for simulating phase changes and varied materials

The disclosure provides an approach for simulating and rendering granular materials. A simulation application generates video frames depicting a granular material phenomenon using a strain based elasto-plastic constitutive model integrated with a hybrid Eulerian/Lagrangian material point method (MPM). The elasto-plastic constitutive model includes physical equation(s) which dictate forces that affect the granular material during the simulation. In particular, the constitutive model may include user-controllable parameters defining threshold(s) to start plastic deformation, as well as a hardening parameter which controls how fast the granular material packs under compression. The MPM is a procedure in which particles of the granular material and a background grid are coupled, with the grid being used to assist in computing forces dictated by the physical equation(s) of the elasto-plastic constitutive model. In one configuration, the grid may further be rendered with volumetric rendering to generate video frames depicting the granular material.

Material point method for simulation of granular materials

A novel algorithmic framework is presented for the simulation of hyperelastic soft tissues that drastically improves each aspect discussed above compared to existing techniques. The approach is robust to large deformation (even inverted configurations) and extremely stable by virtue of careful treatment of linearization. Additionally, a new multigrid approach is presented to efficiently support hundreds of thousands of degrees of freedom (rather than the few thousands typical of existing techniques) in a production environment. Furthermore, these performance and robustness improvements are guaranteed in the presence of both collision and quasistatic/implicit time stepping techniques. The result is a significant advance in the applicability of hyperelastic simulation to skeleton driven character skinning.

Efficient elasticity for character skinning

A computer graphic system and methods for simulating hair is provided. In accordance with aspects of the disclosure a method for hybrid hair simulation using a computer graphics system is provided. The method includes generating a plurality of modeled hair strands using a processor of the computer graphics system. Each hair strand includes a plurality of particles and a plurality of spring members coupled in between the plurality of particles. The method also includes determining a first position and a first velocity for each particle in the plurality of modeled hair strands using the processor and coarsely modeling movement of the plurality of modeled hair strands with a continuum fluid solver. Self-collisions of the plurality of modeled hair strands are computed with a discrete collision model using the processor.

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Los Angeles, CA, United States of America

Joseph M Teran