Modeling and Rendering of Heterogeneous Translucent Materals Using The Diffusion Equation

• US 20120306878A1
• Filed: 08/13/2012
• Published: 12/06/2012
• Est. Priority Date: 02/29/2008
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Wang, Jiaping, Tong, Xin, Lin, Stephen S., Guo, Baining, Shum, Heung-Yeung, Lin, Zhouchen
• Granted Patent: US 8,730,240 B2
• Time in Patent Office: Days
• US Class Current: 345/426
• CPC Class Codes: G01N 21/47 Scattering, i.e. diffuse reflection G01N21/25, G01N21/41 take precedence G01N21/55 takes precedence
• CPC Class Codes: G01N 21/4738 Diffuse reflection precedence is given to G01N21/55 - G01N21/57 if specular component is taken into consideration, e.g. also for testing fluids, fibrous materials
• CPC Class Codes: G06T 15/50 Lighting effects
• CPC Class Codes: G06T 15/506 Illumination models

Abstract

An exemplary method includes providing image data for an illuminated physical sample of a heterogeneous translucent material, determining one or more material properties of the material based in part on a diffusion equation where one of the material properties is a diffusion coefficient for diffusion of radiation in the material and where the determining includes a regularization term for the diffusion coefficient, mapping the one or more material properties to a virtual object volume, assigning virtual illumination conditions to the virtual object volume, and rendering the virtual object volume using the virtual illumination conditions as a boundary condition for a system of diffusion equations of the virtual object volume. Other methods, devices and systems are also disclosed.

Claims

1. A method, implemented at least in part by a computing device, the method comprising:

mapping diffusion coefficients and absorption coefficients for a heterogeneous translucent material to a virtual object volume;

assigning virtual illumination conditions to the virtual object volume; and

rendering the virtual object volume using the virtual illumination conditions as a boundary condition for a system of diffusion equations of the virtual object volume.

2. The method of claim 1, wherein the rendering comprises a finite difference method.

3. The method of claim 1, wherein the rendering comprises a three-dimensional polygrid that comprises interior nodes and boundary nodes to represent the boundary condition.

4. The method of claim 1, wherein the rendering comprises a graphics processor unit (GPU)-based technique wherein material parameters for a polygrid representation of the virtual object volume are packed into a set of 2D textures.

5. The method of claim 1, further comprising:

reassigning virtual illumination conditions; and

rendering the virtual object volume using the prior rendering for initial conditions.

6. The method of claim 1, further comprising:

moving the virtual object volume; and

rendering the virtual object volume using the prior rendering for initial conditions.

7. The method of claim 1, further comprising:

changing one or more coefficients for the virtual object volume; and

rendering the virtual object volume in real-time.

8. The method of claim 1, further comprising:

providing a graphical user interface that comprises tools to change one or more coefficients for the virtual object volume.

9. A method for processing diffusion equations on a graphical processing unit, the method comprising:

constructing a polygrid representation of a virtual object volume wherein the polygrid comprises regular connectivity;

assigning diffusion properties to nodes of the polygrid;

packing the diffusion properties of the polygrid for efficient access by a graphical processing unit; and

solving the diffusion equation and its corresponding boundary condition for the polygrid representation of the virtual object volume, as a system of linear equations with the packed diffusion properties, using the graphical processing unit.

10. The method of claim 9, further comprises:

modifying the polygrid representation of the virtual object volume.

11. The method of claim 9, further comprises:

modifying the polygrid representation of the virtual object volume to cause each boundary node to be linked with an adjacent interior node.

12. The method of claim 11, wherein the modifying the polygrid comprises removing nodes from the polygrid representation.

13. The method of claim 11, wherein the modifying the polygrid comprises adjusting links between nodes in the polygrid representation.

14. The method of claim 11, wherein the modifying the polygrid comprises removing nodes from the polygrid representation based at least in part on grid convexity.

15. The method of claim 11, wherein the modifying the polygrid comprises adjusting links between nodes in the polygrid representation based at least in part on grid convexity.

16. The method of claim 9, wherein the packing the diffusion properties comprises:

packing the diffusion properties into textures.

17. The method of claim 9, wherein the solving the diffusion equation and its corresponding boundary condition comprises:

using a relaxation scheme.

18. The method of claim 9, wherein the nodes of the polygrid comprise:

three or more node types, wherein each of the three or more node types is rendered using a different geometric primitive.

19. A hierarchical method for rendering a virtual object volume, implemented at least in part by a computing device, the method comprising:

constructing a multiresolution polygrid in the virtual object volume;

generating texture pyramids for material properties of the virtual object volume; and

rendering the virtual object volume by solving diffusion equations at a coarse grid level and computing radiant fluence at a finer grid level.

20. The hierarchical method of claim 19, further comprising accelerating the rendering using an adaptive scheme that comprises computing light diffusion at different resolutions at different depths in the virtual object volume.