Mid-field and far-field irradiance approximation

• US 7,995,059 B1
• Filed: 06/08/2007
• Issued: 08/09/2011
• Est. Priority Date: 06/09/2006
• Status: Active Grant

• Current Assignee: Pixar (The Walt Disney Company)
• Original Assignee: Pixar (The Walt Disney Company)
• Inventors: Arvo, Jim
• Primary Examiner(s): Nguyen; Kimbinh T
• Application Number:
  US11/760,522
• Time in Patent Office: 1,523 Days
• Field of Search: 345/419, 345/426, 345/581, 345/582, 345/427, 382/117, 356/511
• US Class Current: 345/426
• CPC Class Codes: G06T 15/506 Illumination models

Abstract

A method for a computer system includes retrieving from a computer readable medium a first irradiance approximation for a plurality of light sources for a first distance in the midfield from the light sources; retrieving from the computer readable medium a second irradiance approximation for the plurality of light sources for a second distance in the farfield, where the second distance is greater than the first distance; and interpolating the first irradiance approximation and the second irradiance approximation to generate a third irradiance approximation for a point having a third distance from the light sources.

Claims

1. A computer method operable on a computer comprises:

retrieving by the computer from a computer readable medium a first irradiance approximation for a plurality of light sources for a first distance in the midfield from the light sources;

retrieving by the computer from the computer readable medium a second irradiance approximation for the plurality of light sources for a second distance in the farfield, where the second distance is greater than the first distance; and

interpolating by the computer the first irradiance approximation and the second irradiance approximation for a point having a third distance from the light sources; and

generating from the interpolation of the first irradiance approximation and the second irradiance approximation a third irradiance approximation for the point having the third distance from the light sources.

2. The computer method of claim 1, wherein the third distance is greater than the first distance and less than the second distance.

3. The computer method of claim 2, further comprising rendering an image for the point based on interpolation step.

4. The computer method of claim 2, wherein the first irradiance approximation is for a first sphere around the plurality of light sources;

and wherein the second irradiance approximation is for a second sphere around the plurality of light sources.

5. The computer method of claim 2, wherein the interpolating step includes:

diminishing the irradiance associated with the first irradiance approximation with a first function of a first radial distance from the first sphere to the point, and

diminishing the irradiance associated with the second irradiance approximation with a second function of a second radial distance from the second sphere to the point.

6. The computer method of claim 5, wherein the first function diminishes the irradiance associated with the first irradiance approximation at a higher rate than the second function diminishes the irradiance associated with the second irradiance approximation.

7. The computer method of claim 6, wherein the first function is proportional to the inverse of the first radial distance cubed.

8. The computer method of claim 7, wherein the second function is proportional to the inverse of the second radial distance squared.

9. A computer program product storable on a non-transitory computer readable memory comprises:

code for retrieving from a computer readable medium a first irradiance approximation for a plurality of light sources for a first distance in the midfield from the light sources;

code for retrieving from the computer readable medium a second irradiance approximation for the plurality of light sources for a second distance in the farfield, where the second distance is greater than the first distance; and

code for interpolating by the computer the first irradiance approximation and the second irradiance approximation for a point having a third distance from the light sources; and

code for generating from the interpolation of the first irradiance approximation and the second irradiance approximation a third irradiance approximation for the point having the third distance from the light sources.

10. The computer program product of claim 9, wherein the third distance is greater than the first distance and less than the second distance.

11. The computer program product of claim 10, further comprising rendering an image for the point based on interpolation step.

12. The computer program product of claim 10, wherein the first irradiance approximation is for a first sphere around the plurality of light sources;

and wherein the second irradiance approximation is for a second sphere around the plurality of light sources.

13. The computer program product of claim 10, wherein the interpolating step includes:

diminishing the irradiance associated with the first irradiance approximation with a first function of a first radial distance from the first sphere to the point, and

diminishing the irradiance associated with the second irradiance approximation with a second function of a second radial distance from the second sphere to the point.

14. The computer program product of claim 13, wherein the first function diminishes the irradiance associated with the first irradiance approximation at a higher rate than the second function diminishes the irradiance associated with the second irradiance approximation.

15. The computer program product of claim 14, wherein the first function is proportional to the inverse of the first radial distance cubed.

16. The computer program product of claim 15, wherein the second function is proportional to the inverse of the second radial distance squared.

17. A computer system comprises:

a processor for executing computer code;

a memory for storing the computer code;

a bus system for transferring the computer code from the memory to the processor for processing,

wherein the processor is configured for;

retrieving from a computer readable medium a first irradiance approximation for a plurality of light sources for a first distance in the midfield from the light sources;

retrieving from the computer readable medium a second irradiance approximation for the plurality of light sources for a second distance in the farfield, where the second distance is greater than the first distance;

interpolating the first irradiance approximation and the second irradiance approximation to generate a third irradiance approximation for a point having a third distance from the light sources;

code for rendering an image for the point based on the code for the interpolation; and

code for storing image information for the point in the memory.

18. The computer system of claim 17, wherein the third distance is greater than the first distance and less than the second distance.

19. The computer system of claim 18, wherein the processor is further configured for rendering an image for the point based on the interpolation step.

20. The computer system of claim 18, wherein the first irradiance approximation is for a first sphere around the plurality of light sources;

and wherein the second irradiance approximation is for a second sphere around the plurality of light sources.

21. The computer system of claim 18, wherein the processor in the interpolating step is further configured for:

diminishing the irradiance associated with the first irradiance approximation with a first function of a first radial distance from the first sphere to the point, and

diminishing the irradiance associated with the second irradiance approximation with a second function of a second radial distance from the second sphere to the point.

22. The computer system of claim 21, wherein the first function diminishes the irradiance associated with the first irradiance approximation at a higher rate than the second function diminishes the irradiance associated with the second irradiance approximation.

23. The computer system of claim 22, wherein the first function is proportional to the inverse of the first radial distance cubed.

24. The computer system of claim 23, wherein the second function is proportional to the inverse of the second radial distance squared.