Apparatus and method for representation of expression in a tissue-like system

• US 6,064,390 A
• Filed: 07/25/1997
• Issued: 05/16/2000
• Est. Priority Date: 07/26/1996
• Status: Expired due to Term

• Current Assignee: Auckland UniServices Limited (Auckland University)
• Original Assignee: Lifef/X Networks, Inc.
• Inventors: Gulas, Ivan, Sagar, Mark A.
• Primary Examiner(s): Powell, Mark R.
• Assistant Examiner(s): MANCUSO, HUEDUNG XUAN CAO
• Application Number:
  US08/900,893
• Time in Patent Office: 1,026 Days
• Field of Search: 345/420, 345/441, 345/442, 345/472, 345/473, 345/474, 345/425
• US Class Current: 345/420
• CPC Class Codes: G06T 13/20 3D [Three Dimensional] animation
• CPC Class Codes: G06T 17/20 Finite element generation, e.g. wire-frame surface description, tesselation

Abstract

An apparatus and method for representing expression in a tissue-like system, that may include a human face, where the system is particularized to a specified individual. A graphical representation generator implemented in a computer determines a representation, in terms of a finite-element model, of the surface of the tissue of the system, providing a graphic output defining the surface in world coordinates. An expressive detail generator, including a wrinkle generator, modifies the surface determined by the graphical representation generator before the surface has been mapped into world coordinates in accordance with three-dimensional features of the tissue-like system of a particular subject.

Claims

1. Apparatus for representation of expression in a particular tissue-like system, the apparatus comprising:

a. a finite-element model of a tissue-like system implemented in a computer, the model having

i. a data input for parameter values defining tissue properties for the particular system;

ii. a command input for identifying an expression to be represented; and

iii. a finite-element output specifying field values, associated with tissue of the system, in finite-element coordinates;

b. a graphical representation generator, implemented in a computer and coupled to the finite-element output, for determining a surface of tissue of the system and providing a graphic output defining the surface in world coordinates; and

c. an expressive detail generator, implemented in a computer and coupled to the finite-element output, for generating expressive detail by modifying the surface determined by the graphical representation generator, wherein the expressive detail generator employs an anisotropic model of tissue, and a wrinkle generator, the wrinkle generator including;

i. an arrangement for computing a field of a strain-related quantity for each of a plurality of finite elements based on the finite-element output; and

ii. an arrangement for modifying the surface of tissue as computed in the graphical representation generator in finite-element coordinates before the surface has been mapped into world coordinates;

so as to produce tissue surface modifications that are not limited to effects caused by movement of, and volume changes in, any underlying musculature.

2. Apparatus according to claim 1, wherein the finite-element model, the graphic representation generator, and the expressive detail generator are configured to provide time-varying outputs so that the graphic output represents an expression that is time-dependant.

3. Apparatus according to claim 1, wherein the tissue-like system has properties similar to those of collagen fibers in tissue and the anisotropic model is based principally on fiber direction associated with the tissue-like system.

4. Apparatus for representation of expression in a particular tissue-like system, the apparatus comprising:

a. a finite-element model of a tissue-like system, implemented in a computer, the model having

i. a data input for parameter values defining tissue properties for the particular system;

ii. a command input for identifying an expression to be represented;

iii. a finite-element output specifying field values, associated with tissue of the system, in finite-element coordinates; and

iv. an arrangement providing a volumetric and anisotropic model of tissue based principally on collagen fiber direction that includes computation of a field of a strain-related quantity for each of a plurality of finite elements, configured so that tissue deformation may result in wrinkles; and

b. a graphical representation generator, implemented in a computer and coupled to the finite-element output, for determining a surface of tissue of the system and providing a graphic output defining the surface in world coordinates;

as to produce tissue surface modifications that are not limited to effects caused by movement of, or volume changes in, any underlying musculature.

5. Apparatus according to claim 4, wherein the tissue-like system has properties similar to those of collagen fibers in tissue and wherein the anisotropic model is based principally on fiber direction associated with the tissue-like system.

6. Method for representing expression in a tissue-like system pertaining to a particular subject, the method comprising:

a. generating a volumetric finite element mesh of the tissue-like system, the volumetric finite element mesh having elements and containing multiple fields of parameters definable across the elements including a height field;

b. measuring three-dimensional features of the particular subject;

c. fitting the volumetric finite element mesh to the three-dimensional features of the particular subject in terms of a fiber coordinate system;

d. calculating a wrinkle map characterizing the particular subject and having wrinkles;

e. isolating positions of the wrinkles into height fields of the finite element mesh; and

f. converting tissue compression based on command data or stored data to the fiber coordinate system; and

g. calculating displacement magnitudes of the height field;

so as to produce tissue surface modifications that are not limited to effects caused by movement of, or volume changes in, any underlying musculature.

7. A method according to claim 6, further including the step of displaying the calculated displacement magnitudes.