Volumetric three-dimensional fog rendering technique

• US 6,268,861 B1
• Filed: 08/25/1998
• Issued: 07/31/2001
• Est. Priority Date: 08/25/1998
• Status: Expired due to Term

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Silicon Graphics Incorporated (Graphics Properties Holdings, Inc.)
• Inventors: Sanz-Pastor, Nacho, Barcena, Luis A.
• Primary Examiner(s): Zimmerman, Mark
• Assistant Examiner(s): Santiago, Enrique L
• Application Number:
  US09/139,961
• Time in Patent Office: 1,071 Days
• Field of Search: 345/430, 345/425, 345/426, 345/431, 345/432, 345/424
• US Class Current: 345/426
• CPC Class Codes: G06T 15/503 Blending, e.g. for anti-aliasing

Abstract

A method and apparatus for volumetric three-dimensional fog rendering is provided. To add fog effects to an image, a host processor computes the location of the eye-point relative to the image to be fogged. Using the eye-point location, the host processor generates a three-dimensional fog texture and a blending function. The three-dimensional fog texture and blending function are downloaded or otherwise passed by the host processor to the graphics processor. The graphics processor then renders the primitives that make up the image. When rendering is complete, the graphics processor applies the tree-dimensional fog texture in an additional rendering pass. The method may then be repeated, to create animated fog effects such as swirling or wind-driven fog.

Claims

1. A method for applying fog to an image, comprising:

(a) calculating, by a host processor, a location of an eye-point relative to the image;

(b) based on the location of the eye-point, generating, by the host processor, a three-dimensional fog texture having a shape of a portion of a volumetric fog definition of the image by volumetric rendering of the volumetric fog definition;

(c) rendering, by a graphics processor, the image;

(d) defining, by the host processor, a blending function for the three-dimensional fog texture; and

(e) applying, by the graphics processor, the three-dimensional fog texture to the image by use of the blending function.

2. A method as recited in claim 1, further comprising downloading, by the host processor, the three-dimensional fog texture to the graphics processor.

3. A method as recited in claim 1, further comprising repeating steps (a) through (e) to provide an animated fog effect.

4. A method as recited in claim 1, further comprising repeating steps (a) through (e) to account for changes in the location of the eye-point.

5. A method as recited in claim 1, wherein the portion of the volumetric fog definition has a cubic shape.

6. A method as recited in claim 5, further comprising changing, by the host processor, the volumetric fog definition to produce animated fog effects.

7. A method as recited in claim 1, wherein the portion of the volumetric fog definition has a truncated pyramid shape.

8. A computer program product comprising:

a computer usable medium having computer readable code embodied therein for adding fog to an image, the computer program product comprising;

first computer readable program code devices configured to cause a host processor to calculate a location of an eye-point relative to the image;

second computer readable program code devices configured to cause the host processor to, based on the location of the eye-point, generate a three-dimensional fog texture having a shape of a portion of a volumetric fog definition of the image by volumetric rendering of the volumetric fog definition;

third computer readable program code devices configured to cause a graphics processor to render the image;

fourth computer readable program code devices configured to cause the host processor to define a blending function; and

fifth computer readable program code devices configured to cause the graphics processor to apply the three-dimensional fog texture to the image using the blending function.

9. A computer program product as recited in claim 8 further comprising sixth computer readable program code devices configured to cause the host processor to download the three-dimensional fog texture to the graphics processor.

10. A computer program product as recited in claim 8 wherein the first through fifth computer readable program code devices are configured to operated on a frame-by-frame basis.

11. A computer program product as recited in claim 8 wherein the second computer readable program code devices are configured to cause the host processor to generate the three-dimensional fog texture by volumetric rendering of a volumetric fog definition of the image.

12. A computer program product as recited in claim 11 further comprising seventh computer readable program code devices configured to cause the host processor to change the volumetric fog definition to produce animated fog effects.

13. An apparatus for adding fog to an image, comprising:

a first portion configured to calculate a location of an eye-point relative to the image;

a second portion configured to generate, based on the location of the eye-point, a three-dimensional fog texture having a shape of a portion of a volumetric fog definition of the image by volumetric rendering of the fog definition;

a third portion configured to render the image;

a fourth portion configured to define a blending function; and

a fifth portion configured to apply the three-dimensional fog texture to the image using the blending function.

14. An apparatus as recited in claim 13 further comprising a sixth portion configured to download the three-dimensional fog texture to the graphics processor.

15. An apparatus as recited in claim 13 wherein the first through fifth portions are configured to operated on a frame-by-frame basis.

16. An apparatus as recited in claim 13 wherein the portion of the volumetric fog has a cubic shape.

17. An apparatus as recited in claim 16 further comprising a portion configured to change the volumetric fog definition to produce animated fog effects.

18. An apparatus as recited in claim 13, wherein the portion of the volumetric fog definition has a truncated pyramid shape.