Method and apparatus for performing H-space bump mapping suitable for implementation with H-space lighting in a graphics pipeline of a computer graphics display system

• US 6,518,968 B1
• Filed: 05/17/2000
• Issued: 02/11/2003
• Est. Priority Date: 05/17/2000
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Cunniff, Ross, Ritter, Bradford A.
• Primary Examiner(s): Vo, Cliff N.
• Application Number:
  US09/573,059
• Time in Patent Office: 1,000 Days
• Field of Search: 345/418, 345/419, 345/426, 345/427
• US Class Current: 345/426
• CPC Class Codes: G06T 15/04 Texture mapping

Abstract

The present invention provides a method and apparatus for performing H-space bump mapping. The apparatus of the present invention is a fragment processor of a computer graphics display system. The method of the present invention is performed by the fragment processor. In accordance with the method of the present invention, for each vertex of each polygon being processed, the fragment processor calculates both diffuse and specular lighting terms. Then, for each fragment within the polygon defined by the vertices, the fragment processor interpolates the specular and diffuse lighting terms to obtain diffuse and specular lighting terms for each fragment. If bump mapping has been enabled, the fragment processor adds perturbations to the diffuse and specular lighting terms to generate the bump mapping. Preferably, prior to performing the H-space bump mapping algorithm, texture coordinate gradient vectors are calculated for the image to be rendered. During the H-space bump mapping algorithm of the present invention, the H-space reference vectors are aligned with the texture coordinate gradient vectors. The specular and diffuse lighting terms are calculated using the H-space reference vectors. Since the H-space reference vectors are aligned with the texture coordinate vectors, it is not necessary to transform the specular and diffuse lighting terms into the coordinate system associated with the texture coordinates of the bump map on a per fragment (i.e., per pixel basis). Once the H-space reference vectors have been aligned with the texture coordinate gradient vectors, the algorithm proceeds in the aforementioned manner.

Claims

1. An apparatus for performing H-space lighting and bump mapping for an image to be rendered, the apparatus comprising a fragment lighting component, the fragment lighting component comprising:

logic that computes H-space specular and diffuse lighting terms for each vertex of a polygon being processed by the fragment lighting component; and

logic that interpolates the H-space specular and diffuse lighting terms for each pixel within a region encompassed by the polygon being processed.

2. The apparatus of claim 1, further comprising logic that adds perturbations to the interpolated specular and diffuse lighting terms to effectuate bump mapping.

3. The apparatus of claim 2, wherein prior to computing the H-space specular and diffuse lighting terms, the fragment lighting component aligns H-space vertex reference vectors with texture coordinate gradient vectors, wherein once the H-space vertex reference vectors have been aligned with the texture coordinate gradient vectors, the logic that computes H-space specular and diffuse lighting terms computes the specular and diffuse lighting terms for each vertex of the polygon being processed using the aligned H-space vertex reference vectors.

4. The apparatus of claim 3, wherein once the logic that computes H-space specular and diffuse lighting terms has computed the aligned H-space vertex reference vectors and has computed the H-space specular and diffuse lighting terms associated with the vertices of the polygon being processed, the logic that interpolates the H-space specular and diffuse lighting terms utilizes the H-space specular and diffuse lighting terms associated with the vertices of the polygon being processed to interpolate the H-space specular and diffuse lighting terms of the pixels within the polygon.

5. The apparatus of claim 4, wherein the logic that adds perturbations is capable of being controlled such that perturbations are added to the H-space specular and/or diffuse lighting terms.

6. The apparatus of claim 5, wherein the fragment lighting component is comprised as part of a graphics pipeline of a computer graphics display system.

7. The apparatus of claim 6, wherein each logic is implemented in hardware.

8. The apparatus of claim 2, wherein the computed H-space specular and diffuse lighting terms define a two-dimensional representation of at least one three-dimensional vector indicative of light direction.

9. The apparatus of claim 8, wherein the three-dimensional vector is a half-angle vector associated with a light vector and a view vector.

10. A computer graphics display system comprising a graphics system that processes image data associated with an image to be rendered on a display device of the computer graphics display system, said graphics system being capable of performing H-space lighting and bump mapping, said graphics system comprising:

a fragment lighting component comprising logic for computing H-space specular and diffuse lighting terms for each vertex of a polygon being processed by the fragment lighting component and logic for interpolating the H-space specular and diffuse lighting terms for each pixel within a region encompassed by the polygon being processed.

11. The apparatus of claim 10, further comprising logic configured to add perturbations to the interpolated specular and diffuse lighting terms to effectuate bump mapping.

12. The computer graphics display system of claim 11, wherein prior to computing the H-space specular and diffuse lighting terms, the fragment lighting component aligns H-space vertex reference vectors with texture coordinate gradient vectors, wherein once the H-space vertex reference vectors have been aligned with the texture coordinate gradient vectors, the logic for computing H-space specular and diffuse lighting terms computes the H-space specular and diffuse lighting terms for each vertex of the polygon being processed using the aligned H-space vertex reference vectors.

13. The computer graphics display system of claim 12, wherein once the logic for computing specular and diffuse lighting terms has computed the aligned H-space vertex reference vectors and has computed the specular and diffuse lighting terms associated with the vertices of the polygon being processed, the logic for interpolating the specular and diffuse lighting terms utilizes the H-space specular and diffuse lighting terms associated with the vertices of the polygon being processed to interpolate the H-space specular and diffuse lighting terms of the pixels within the polygon.

14. The computer graphics display system of claim 13, wherein the logic for adding perturbations is capable of being controlled such that perturbations are added to the H-space specular and/or diffuse lighting terms, thereby enabling the effect of bump mapping to be controlled.

15. The computer graphics display system of claim 14, wherein the fragment lighting component is implemented in hardware.

16. A method for performing H-space lighting and bump mapping for an image to be rendered, the method being implemented in a fragment lighting component, the method comprising the steps of:

computing H-space specular and diffuse lighting terms for each vertex of a polygon being processed by the fragment lighting component; and

interpolating the H-space specular and diffuse lighting terms for each pixel within a region encompassed by the polygon being processed.

17. The apparatus of claim 16, further comprising adding perturbations to the interpolated specular and diffuse lighting terms to effectuate bump mapping.

18. The method of claim 17, wherein prior to computing the H-space specular and diffuse lighting terms for each vertex, H-space vertex reference vectors are aligned with texture coordinate gradient vectors, wherein once the H-space vertex reference vectors have been aligned with the texture coordinate gradient vectors, the H-space specular and diffuse lighting terms are computed for each vertex of the polygon being processed using the aligned H-space vertex reference vectors.

19. The method of claim 18, wherein once the H-space specular and diffuse lighting terms associated with the vertices of the polygon being processed have been computed, the specular and diffuse lighting terms associated with the vertices of the polygon being processed are used to interpolate the H-space specular and diffuse lighting terms of the pixels within the polygon.

20. The method of claim 19, wherein the process of adding perturbations to the H-space specular and/or diffuse lighting terms can be controlled so that the H-space specular and/or diffuse lighting terms can be controllably bump-mapped.

21. The method of claim 20, wherein the steps of computing H-space specular and diffuse lighting terms for each vertex of a polygon being processed by the fragment lighting component, of interpolating the H-space specular and diffuse lighting terms for each pixel within a region encompassed by the polygon being processed, and of adding perturbations to the H-space specular and diffuse lighting terms to effectuate bump mapping, are performed in hardware.

22. The method of claim 20, wherein the steps of computing H-space specular and diffuse lighting terms for each vertex of a polygon being processed by the fragment lighting component, of interpolating the s H-space specular and diffuse lighting terms for each pixel within a region encompassed by the polygon being processed, and of adding perturbations to the H-space specular and diffuse lighting terms to effectuate bump mapping, are performed in software.

23. A computer program for performing H-space lighting and bump mapping for an image to be rendered, the computer program being embodied on a computer-readable medium, the program comprising:

a code segment for computing H-space specular and diffuse lighting terms for each vertex of a polygon being processed;

a code segment for interpolating the H-space specular and diffuse lighting terms for each pixel within a region encompassed by the polygon being processed; and

a code segment for causing perturbations to be added to the H-space specular and/or diffuse lighting terms to effectuate bump mapping.

24. The computer program of claim 23, further comprising a code segment for determining texture coordinate gradient vectors associated with the image to be rendered and aligns H-space vertex reference vectors with the texture coordinate gradient vectors prior to computing the H-space specular and diffuse lighting terms for each vertex, wherein once the H-space vertex reference vectors have been aligned with the texture coordinate gradient vectors, the H-space specular and diffuse lighting terms are computed for each vertex of the polygon being processed using the aligned H-space vertex reference vectors.

25. The computer program of claim 24, wherein the code segment for adding perturbations controllably adds perturbations to the H-space specular and/or diffuse lighting terms such that the H-space specular and/or diffuse lighting terms are controllably bump-mapped.

26. The computer program of claim 25, wherein the computer program is executed by a host central processing unit of a computer graphics display system.