Styling of computer graphics hair through volumetric flow dynamics

Number: 9710966
Published: 2017-07-18
Filed: 2014-09-16
Assignee: LUCASFILM ENTERTAINMENT COMPANY LTD.
Inventors: Bowline; Stephen D., Rasmussen; Nicholas Grant
CPC: G06T17/20; G06T13/40
Verdict: Low Notable software
Source: Google Patents · FreePatentsOnline

The keeper's note

Generates realistic CG hair/fur strand geometry using a fluid flow simulation within a defined hair volume.

Abstract

Methods are disclosed for the computer generation of data for images that include hair, fur, or other strand-like material. A volume for the hair is specified,having a plurality of surfaces. A fluid flow simulation is performed within the volume, with a first surface of the volume being a source area through which fluid is simulated to enter the volume, and a second surface being an exit surface through which fluid is simulated as exiting the volume. The fluid flow simulation may be used to produce fluid flow lines, such as from a velocity vector field for the fluid. Fluid flow lines are selected, andimage data of hairs that follow the fluid flow lines are generated. Other embodiments include generating animation sequences by generating images wherein the volume and surfaces vary between frames.

Background

BRIEF DESCRIPTION OF THE DRAWINGS(1) FIG. 1A illustrates a method of generating image data of hair on a character as simulated by a fluid flow within a volume, according to an embodiment.(2) FIG. 1B illustrates samples of a vector field corresponding to a fluid flow in a cylindrical frustrum.(3) FIG. 2 is a flow chart of a method for generation of data for images of objects comprising hair or fur, according to an embodiment.(4) FIG. 3A illustrates a tessellated surface component of an object, according to an embodiment.(5) FIG. 3B illustrates a rendering of a tessellated surface component of an object comprising a source area from which hair growth is to be simulated, according to an embodiment.(6) FIG. 3C shows a rendering of a tessellated surface component of an object comprising a source area, according to an embodiment.(7) FIG. 4A illustrates a three-dimensional (3D) hair volume and components of a fully-closed polyhedral hair mesh that subdivides the 3D hair volume, according to embodiments.(8) FIG. 4B shows a rendering of a view of a tessellated surface of an object from which a 3D hair volume is extended, according to an embodiment.(9) FIG. 5 illustrates a tessellated surface component of an object with entry flow vectors, according to an embodiment.(10) FIG. 6A illustrate a cut-away view of a 3D hair volume with simulated fluid flow lines extending from a source area to an exit area, according to an embodiment.(11) FIG. 6B shows a rendering of exit flow vectors on a 3

Claims

1. A method of generating image data for hair on a character, the character having a surface component represented by a two-dimensional (2D) polygonal character surface mesh within a three-dimensional (3D) space, the method comprising: adding a fully closed 3D polyhedral hair mesh to the 2D polygonal character surface mesh, thefully closed polyhedral 3D hair mesh including a surface comprising a source area at the interface between the 2D polygonal mesh and the fully closed 3D polyhedral hair mesh, one or more exit areas disjoint from the source area, and one or more boundary surfaces between the source area and the one or more exit areas; defining a plurality of fluid entrance points along the source area; defining a plurality of fluid exit points along the one or more exit areas; generating a plurality of fluid flow lines through the fully closed 3D polyhedral hair mesh by simulating a flow of fluid through the fully closed 3D polyhedral hairmesh from the plurality of fluid entrance points to the plurality of fluid exit points, wherein the flow of fluid is bounded within the fully closed 3D polyhedral hair mesh by theone or more boundary surfaces; determining a subset of the plurality of fluid flow lines that are visible from a viewpoint; and forming image data for a plurality of hairs, wherein each of the plurality of hairs extends along a respective fluid flow line from the subset of the plurality of fluid flow lines. 9. A method of generating image data of hair in a three-dimensional (3D) hair volume comprising: receiving a representation of the 3D hair volume, the representation comprising a fully-closed three-dimensional (3D) polyhedral hairmesh of the 3D hair volume, wherein a first surface region of the 3D hair volume conformsto a surface component of the object; identifying a part of the first surface region as asource area; identifying a second surface region of the 3D hair volume, disjoint from thefirst surface region, as an exit area; simulating a fluid flow within the 3D hair volume using the 3D polyhedral hair mesh such that in the fluid flow simulation the fluid enters the 3D hair volume only through the source area, the fluid exits the hair volume only through the exit area, and the fluid flow is bounded in the 3D hair volume; generating a plurality of fluid flow lines through the 3D hair mesh using data of the fluid flow simulation;determining a subset of the plurality of fluid flow lines that are visible from a viewpoint; and forming image data for a plurality of hairs so that each of the plurality of hairsextends along a respective fluid flow line from the subset of the plurality of fluid flowlines.