Skin and flesh simulation using finite elements, biphasic materials, and rest state retargeting

Patent metadata

Field	Value
Publication number	US-9251618-B2
Application number	US-201313843923-A
Country	US
Kind code	B2
Filing date	Mar 15, 2013
Priority date	Jun 27, 2012
Publication date	Feb 2, 2016
Grant date	Feb 2, 2016

Abstract

The movement of skin on an animated target, such as a character or other object, is simulated via a simulation software application. The software application creates a finite element model (FEM) comprising a plurality of finite elements based on an animated target. The software application attaches a first constraint force to a node associated with a first finite element in the plurality of finite elements. The software application attaches a second constraint force to the node. The software application detects a movement of the first finite element that results in a corresponding movement of the node. The software application determines a new position for the node based on the movement of at least one of the first finite element, the first constraint force, and the second constraint force.

First claim

What is claimed is:

1. A method of rendering a material associated with an animated target, the method comprising:
creating a finite element model (FEM) comprising a plurality of finite elements based on an animated target;
attaching, via one or more processors, a first constraint force to a node associated with a first finite element in the plurality of finite elements, the first constraint force being a sliding force that is normal to a surface of the animated target and projects nodes of the FEM onto the animated target;
attaching, via the one or more processors, a second constraint force to the node, the second constraint force being a targeting force that is tangential to the surface of the animated target and attempts to return nodes of the FEM to where corresponding points in the animated target are located;
detecting a movement of the first finite element that results in a corresponding movement of the node;
determining a new position for the node based on the movement of at least one of the first finite element, the first constraint force, and the second constraint force; and
rendering one or more image frames depicting the material based on at least the new position for the node,
wherein the FEM is coupled to a biphasic material used to model the material associated with the animated target, and
wherein a value for a parameter, which is associated with the biphasic material and changes as a displacement of the biphasic material increases, is determined based on whether or not a deformation of the biphasic material is below a threshold amount.

2. The method of claim 1 , wherein the parameter of the biphasic material is one of a stiffness of the biphasic material, a hardness of the biphasic material, or a Young's modulus associated with the biphasic material.

3. The method of claim 1 , wherein the new position for the node is further based on the deformation of the biphasic material.

4. The method of step 1 , further comprising altering the shape of the FEM based on a target rest state associated with the animated target.

5. The method of claim 1 , further comprising simulating the first constraint force by solving a system of closed form equations related to the first constraint force.

6. The method of claim 1 , further comprising simulating the second constraint force via semi-implicit time integration with a time step associated with a simulation program.

7. The method of claim 1 , further comprising simulating the movement of the FEM via fully explicit integration with a time step associated with the a simulation program.

8. A non-transitory computer-readable storage medium including instructions that, when executed by a processing unit, cause the processing unit to render a material associated with an animated target, by performing the steps of:
creating a finite element model (FEM) comprising a plurality of finite elements based on an animated target;
attaching a first constraint force to a node associated with a first finite element in the plurality of finite elements, the first constraint force being a sliding force that is normal to a surface of the animated target and projects nodes of the FEM onto the animated target;
attaching a second constraint force to the node, the second constraint force being a targeting force that is tangential to the surface of the animated target and attempts to return nodes of the FEM to where corresponding points in the animated target are located;
detecting a movement of the first finite element that results in a corresponding movement of the node;
determining a new position for the node based on the movement of at least one of the first finite element, the first constraint force, and the second constraint force; and
rendering one or more image frames depicting the material based on at least the new position for the node,
wherein the FEM is coupled to a biphasic material used to model the material associated with the animated target, and
wherein a value for a parameter, which is associated with the biphasic material and changes as a displacement of the biphasic material increases, is determined based on whether or not a deformation of the biphasic material is below a threshold amount.

9. The computer-readable storage medium of claim 8 , wherein the parameter of the biphasic material is one of a stiffness of the biphasic material, a hardness of the biphasic material, or a Young's modulus associated with the biphasic material.

10. The computer-readable storage medium of claim 8 , wherein the new position for the node is further based on the deformation of the biphasic material.

11. The computer-readable storage medium of step 8 , further comprising the step of altering the shape of the FEM based on a target rest state associated with the animated target.

12. The computer-readable storage medium of claim 8 , further comprising the step of simulating the first constraint force by solving a system of closed form equations related to the first constraint force.

13. The computer-readable storage medium of claim 8 , further comprising the step of simulating the second constraint force via semi-implicit time integration with a time step associated with a simulation program.

14. The computer-readable storage medium of claim 8 , further comprising the step of simulating the movement of the FEM via fully explicit integration with a time step associated with a simulation program.

15. A computing system, comprising:
a memory that is configured to store instructions for a program; and
a processor that is configured to execute the instructions for the program to render a material associated with an animated target, by performing the steps of:
creating a finite element model (FEM) comprising a plurality of finite elements based on an animated target;
attaching a first constraint force to a node associated with a first finite element in the plurality of finite elements, the first constraint force being a sliding force that is normal to a surface of the animated target and projects nodes of the FEM onto the animated target;
attaching a second constraint force to the node, the second constraint force being a targeting force that is tangential to the surface of the animated target and attempts to return nodes of the FEM to where corresponding points in the animated target are located;
detecting a movement of the first finite element that results in a corresponding movement of the node;
determining a new position for the node based on the movement of at least one of the first finite element, the first constraint force, and the second constraint force; and
rendering one or more image frames depicting the material based on at least the new position for the node,
wherein the FEM is coupled to a biphasic material used to model the material associated with the animated target, and

wherein a value for a parameter, which is associated with the biphasic material and changes as a displacement of the biphasic material increases, is determined based on whether or not a deformation of the biphasic material is below a threshold amount.

Assignees

• Kautzman Ryan
• Chong Jiayi
• Coleman Patrick
• Pixar

Inventors

• Kautzman Ryan
• Chong Jiayi
• Coleman Patrick

Classifications

• G06T13/40 Primary

  of characters, e.g. humans, animals or virtual beings · CPC title

• G06F30/23

  using finite element methods [FEM] or finite difference methods [FDM] · CPC title

• G06F17/5018

  Physics · mapped topic