Translucent object rendering methods and apparatus

• US 7,864,176 B2
• Filed: 10/27/2008
• Issued: 01/04/2011
• Est. Priority Date: 04/30/2003
• Status: Active Grant

• Current Assignee: Pixar (The Walt Disney Company)
• Original Assignee: Pixar (The Walt Disney Company)
• Inventors: Anderson, John R., Planck, Maxwell, Tomson, Erin
• Primary Examiner(s): Broome; Said
• Application Number:
  US12/259,062
• Publication Number:
  US 20090109221A1
• Time in Patent Office: 799 Days
• Field of Search: None
• US Class Current: 345/424
• CPC Class Codes: G06T 15/506 Illumination models

Abstract

A computer system method includes determining a first surface illumination on an object based upon a respective irradiance, determining a first surface reflection based upon the respective irradiance, determining a second surface illumination on the object based upon a respective irradiance, determining a second surface reflection based upon the respective irradiance, receiving a first weighting for the first illumination and the first reflection value, and a second weighting for the second illumination and the second reflection value, wherein the weightings are different, determining a first surface illumination in response to the first illumination value, the first reflection, and the first weighting, determining a second surface illumination in response to the second illumination value, the second reflection, and the second weighting, and determining an image including the object based on the first surface illumination and the second surface illumination.

Claims

1. A computer implemented method performed by a computer system programmed to perform the method comprising:

determining by the computer system a first diffuse illumination compensation value associated with a first surface region on an object in response to an irradiance associated with the first surface region;

determining by the computer system a first diffuse reflection value associated with the first surface region on the object in response to the irradiance associated with the first surface region;

determining by the computer system a second diffuse illumination compensation value associated with a second surface region on the object in response to an irradiance associated with the second surface region;

determining by the computer system a second diffuse reflection value associated with the second surface region on the object in response to the irradiance associated with the second surface region;

receiving by the computer system a specification of a first weighting for the first diffuse illumination compensation value and the first diffuse reflection value, and a second weighting for the second diffuse illumination compensation value and the second diffuse reflection value, wherein the first weighting is different from the second weighting;

determining by the computer system a diffuse illumination value associated with the first surface region on the object in response to the first diffuse illumination compensation value, the first diffuse reflection, and the first weighting;

determining by the computer system a diffuse illumination value associated with the second surface region on the object in response to the second diffuse illumination compensation value, the second diffuse reflection, and the second weighting; and

determining by the computer system an image including a rendered representation of the object in response to the diffuse illumination value associated with the first surface region and to the diffuse illumination value associated with the second surface region.

2. The method of claim 1

wherein determining the first diffuse illumination compensation value associated with the first surface region on the object is also in response to a plurality of voxels having associated subsurface scattering parameters;

and

wherein determining the second diffuse illumination compensation value associated with the second surface region on the object is also in response to the plurality of voxels having associated subsurface scattering parameters.

3. The method of claim 2

wherein the associated subsurface scattering parameters are selected from a group consisting of:

extinction coefficients, scattering lengths.

4. The method of claim 1

wherein receiving the specification of the first weighting comprises receiving the specification in response to a user input;

wherein the user input is selected form a group consisting;

keyboard entry, graphical selection with a user input device.

5. The method of claim 1

wherein the first weighting for the first diffuse illumination compensation value and the first diffuse reflection value comprises a greater percentage of the first diffuse illumination compensation value compared to the first diffuse illumination compensation value;

wherein the second weighting for the second diffuse illumination compensation value and the second diffuse reflection value comprises a smaller percentage of the first diffuse illumination compensation value compared to the first diffuse illumination compensation value.

6. The method of claim 1 further comprising:

displaying by the computer system the image to the user; and

storing by the computer system a representation of the image on a tangible media.

7. A non-transitory computer-readable media comprising executable computer code including:

code that directs the processor to determine a first diffuse illumination compensation value associated with a first surface region of an object in response to an irradiance associated with the first surface region;

code that directs a processor to determine a first diffuse reflection value associated with the first surface region in response to the irradiance associated with the first surface region;

code that directs a processor to determine a second diffuse illumination compensation value associated with a second surface region of the object in response to an irradiance associated with the second surface region;

code that directs a processor to determine a second diffuse reflection value associated with the second surface region in response to the irradiance associated with the second surface region;

code that directs a processor to receive a specification of a first weighting for the first diffuse illumination compensation value and the first diffuse reflection value, and a second weighting for the second diffuse illumination compensation value and the second diffuse reflection value, wherein the first weighting is different from the second weighting;

p1 code that directs a processor to determine a diffuse illumination value associated with the first surface region in response to the first diffuse illumination compensation value, the first diffuse reflection, and the first weighting;

code that directs a processor to determine a diffuse illumination value associated with the second surface region in response to the second diffuse illumination compensation value, the second diffuse reflection, and the second weighting; and

code that directs a processor to determine an image including a rendered representation of the object in response to the diffuse illumination value associated with the first surface region and to the diffuse illumination value associated with the first surface region.

8. A computer implemented method performed by a computer system programmed to perform the method comprising:

receiving by the computer system a specification of a three-dimensional object including a surface region associated with a plurality of materials including a first material and a second material, wherein the first material is associated with a first thickness and is associated with a first value for a subsurface scattering parameter wherein the second material is associated with a second thickness and is associated with a second value for the subsurface scattering parameter, wherein the first value is different from the second value;

determining by the computer system a third value for the subsurface scattering parameter associated with the first material and the second material in response to the first thickness, the first value for the subsurface scattering parameter, the second thickness, and the second value for the subsurface scattering parameter;

determining by the computer system a diffuse illumination compensation value associated with the surface region in response to the third value for the subsurface scattering parameter.

9. The method of claim 8 wherein determining the third value for the subsurface scattering parameter comprises determining by the computer system a weighted thickness average of the first value for the subsurface scattering parameter and the second value for the subsurface scattering parameter.

10. The method of claim 9 wherein determining the diffuse illumination compensation value comprises performing by the computer system a volumetric subsurface scattering computation in response to the third value for the subsurface scattering parameter, to the first thickness, and to the second thickness.

11. The method of claim 10

wherein the first material and the second material underlies the surface region of the three-dimensional object;

wherein the first material is associated with a first volumetric region; and

wherein the second material is associated with a second volumetric region.

12. The method of claim 10 wherein performing the volumetric subsurface scattering computation comprises performing a recursive filtering operation in response to the third value for the subsurface scattering parameter.

13. The method of claim 8 further comprising determining by the computer system an image including a rendered representation of the three-dimensional object in response to the diffuse illumination value associated with the surface region.

14. A non-transitory computer-readable media comprising executable computer code including:

code configured to direct the processor to receive a specification of a three-dimensional object including a surface region associated with a plurality of materials including a first material and a second material, wherein the first material is associated with a first thickness and is associated with a first value for a subsurface scattering parameter wherein the second material is associated with a second thickness and is associated with a second value for the subsurface scattering parameter, wherein the first value is different from the second value;

code configured to direct the processor to determine a third value for the subsurface scattering parameter associated with the first material and the second material in response to the first thickness, the first value for the subsurface scattering parameter, the second thickness, and the second value for the subsurface scattering parameter; and

code configured to direct the processor to determine a diffuse illumination compensation value associated with the surface region in response to the third value for the subsurface scattering parameter.

15. A computer implemented method performed by a computer system programmed to perform the method comprising:

receiving by the computer system a description of a three-dimensional scene including a specification of placement of an object within the three-dimensional scene;

receiving by the computer system a three-dimensional model of an object;

determining by the computer system a resolution for a volumetric grid comprising a plurality of voxels associated with the three-dimensional model of the object in response to the placement of the object within the three-dimensional scene, and in response to the three-dimensional model of the object, wherein each voxels from the plurality of voxels is associated with a subsurface scattering parameter;

determining by the computer system an incident irradiance associated with a plurality of voxels associated with a surface region of the object; and

determining by the computer system a subsurface scattering contribution associated with the plurality of voxels associated with a surface region of the object in response to the incident irradiance and in response to the subsurface scattering parameters associated with the voxels from the plurality of voxels.

16. The method of claim 15 wherein the subsurface scattering parameters associated with the voxels from the plurality of voxels are selected from a group consisting of:

extinction coefficients, scattering lengths.

17. The method of claim 15 wherein determining the resolution for the volumetric grid comprises:

determining by the computer system a size for a voxel in response to the placement of the object within the three-dimensional scene and the three-dimensional model of the object;

determining by the computer system the volumetric grid comprising the plurality of voxels associated with the three-dimensional model of the object in response to the size for the voxel and in response to the three-dimensional model of the object.

18. The method of claim 15 wherein determining the subsurface scattering contribution comprising applying by the computer system a recursive directional low-pass filter on the voxels from the plurality of voxels.

19. The method of claim 15 further comprising:

determining by the computer system an image including a rendered representation of the object in response to the subsurface scattering contribution;

displaying the image to the user; and

storing a representation of the image on a tangible media.

20. A non-transitory computer-readable media including executable computer code, non-transitory computer-readable media comprising:

code configured to direct the processor to receive a description of a three-dimensional scene including a specification of placement of an object within the three-dimensional scene;

code configured to direct the processor to receive a three-dimensional model of an object;

code configured to direct the processor to determine a resolution for a volumetric grid comprising a plurality of voxels associated with the three-dimensional model of the object in response to the placement of the object within the three-dimensional scene, and in response to the three-dimensional model of the object, wherein each voxels from the plurality of voxels is associated with a subsurface scattering parameter;

code configured to direct the processor to determine an incident irradiance associated with a plurality of voxels associated with a surface region of the object; and

code configured to direct the processor to determine a subsurface scattering contribution associated with the plurality of voxels associated with a surface region of the object in response to the incident irradiance and in response to the subsurface scattering parameters associated with the voxels from the plurality of voxels.