System and method for distributing photons when rendering an image using photon mapping

• US 7,221,365 B1
• Filed: 11/23/2004
• Issued: 05/22/2007
• Est. Priority Date: 11/23/2004
• Status: Active Grant

• Current Assignee: Autodesk, Inc.
• Original Assignee: Autodesk, Inc.
• Inventors: Levesque, Daniel, Breton, Pierre Felix, Robillard, Claude
• Primary Examiner(s): Zimmerman; Mark
• Assistant Examiner(s): Santiago; Enrique L.
• Application Number:
  US10/996,594
• Time in Patent Office: 910 Days
• Field of Search: None
• US Class Current: 345/426
• CPC Class Codes: G06T 15/506 Illumination models

Abstract

A method for distributing photons among light sources when rendering an image of a scene using photon mapping includes the steps of computing a total energy for the scene, where the scene includes a plurality of light sources, and computing an average energy of the light sources. The method also includes the steps of comparing, for each of the light sources, the actual energy of the light source to an average energy of the light source and distributing photons to each of the light sources based on the comparison.

Claims

1. A method for distributing photons among light sources when rendering an image of a scene using photon mapping, the method comprising:

computing a total energy for the scene, the scene having a plurality of light sources;

computing an average energy of the light sources;

for each of the light sources, comparing the actual energy of the light source to an average energy of the light source; and

distributing photons to each of the light sources based on the comparison.

2. The method of claim 1, wherein the step of computing a total energy comprises summing together the actual energy of each of the light sources.

3. The method of claim 1, wherein the step of computing an average energy comprises dividing the total energy by the number of light sources in the plurality of light sources.

4. The method of claim 1, wherein the step of comparing comprises computing, for each of the light sources, a ratio of the actual energy of the light source to the average energy of the light source.

5. The method of claim 4, wherein, for each of the light sources, the number of photons distributed equals the product of the ratio associated with the light source and an average number of photons designated for each of the light sources.

6. The method of claim 1, further comprising the step of determining the average number of photons designated for each of the light sources.

7. The method of claim 1, further comprising the step of determining the actual energy of each of the light sources.

8. A method for distributing photons among light sources when rendering an image of a scene using photon mapping, the method comprising:

determining a first actual energy of a first light source and a second actual energy of a second light source;

computing an average energy of the first light source and the second light source;

computing a first ratio associated with the first light source equal to the actual energy of the first light source divided by the average energy; and

distributing to the first light source a number of photons equal to the product of the first ratio and an average number of photons designated for each of the first light source and the second light source.

9. The method of claim 8, further comprising the step of computing a second ratio associated with the second light source equal to the actual energy of the second light source divided by the average energy.

10. The method of claim 9, further comprising the step of distributing to the second light source a number of photons equal to the product of the second ratio and the average number of photons designated for each of the first light source and the second light source.

11. A computer-readable medium storing instructions for causing a computing device to distribute photons among light sources when rendering an image of a scene using photon mapping by performing the steps of:

computing a total energy for the scene, the scene having a plurality of light sources;

computing an average energy of the light sources;

for each of the light sources, comparing the actual energy of the light source to an average energy of the light source; and

distributing photons to each of the light sources based on the comparison.

12. The computer-readable medium of claim 11, wherein the step of computing a total energy comprises summing together the actual energy of each of the light sources.

13. The computer-readable medium of claim 11, wherein the step of computing an average energy comprises dividing the total energy by the number of light sources in the plurality of light sources.

14. The computer-readable medium of claim 11, wherein the step of comparing comprises computing, for each of the light sources, a ratio of the actual energy of the light source to the average energy of the light source.

15. The computer-readable medium of claim 14, wherein, for each of the light sources, the number of photons distributed equals the product of the ratio associated with the light source and an average number of photons designated for each of the light sources.

16. The computer-readable medium of claim 11, further comprising the step of determining the average number of photons designated for each of the light sources.

17. The computer-readable medium of claim 11, further comprising the step of determining the actual energy of each of the light sources.

18. A system for distributing photons among light sources when rendering an image of a scene using photon mapping, the system comprising:

a memory configured to store instructions for rendering the image; and

a processor configured to perform the steps of;

computing a total energy for the scene, the scene having a plurality of light sources;

computing an average energy of the light sources,

for each of the light sources, comparing the actual energy of the light source to an average energy of the light source, and

distributing photons to each of the light sources based on the comparison.

19. The system of claim 18, wherein the step of comparing comprises computing, for each of the light sources, a ratio of the actual energy of the light source to the average energy of the light source.

20. The system of claim 18, wherein, for each of the light sources, the number of photons distributed equals the product of the ratio associated with the light source and an average number of photons designated for each of the light sources.