Apparatus, system, and method for gamma correction of smoothed primitives

• US 7,081,902 B1
• Filed: 09/24/2003
• Issued: 07/25/2006
• Est. Priority Date: 09/24/2003
• Status: Active Grant

• Current Assignee: NVIDIA Corporation
• Original Assignee: NVIDIA Corporation
• Inventors: Craighead, Matthew J., Montrym, John S., Crow, Franklin C.
• Primary Examiner(s): Tung, Kee M.
• Assistant Examiner(s): CASCHERA, ANTONIO A
• Application Number:
  US10/671,237
• Time in Patent Office: 1,035 Days
• Field of Search: 345/549, 345/593, 345594-599, 345/601, 345/639, 345/640
• US Class Current: 345/611
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 2320/0673 for control of gamma adjustment, e.g. selecting another gamma curve
• CPC Class Codes: G09G 5/363 Graphics controllers

Abstract

A graphics processor performed gamma correction of the coverage values of pixels. In one embodiment, a gamma correction factor is written into a run-time loadable lookup table of the graphics processor. The gamma corrected coverage values may be used in an anti-aliasing process to form smoothed primitives.

Claims

1. A method of using a graphics processor to reduce visual artifacts, comprising:

receiving an instruction for selectively enabling gamma correction of a selected class of primitive types, said selected class including at least one member selected from a group of at least two different primitive types;

rasterizing primitives of a graphical image to generate fragments;

for each pixel partially covered by a primitive of a primitive type belonging to said selected class of primitive types, gamma correcting its coverage value to form at least one gamma corrected coverage value; and

for each pixel partially covered by a primitive of a primitive type not belonging to said selected class of primitive types, not gamma correcting its coverage value.

2. The method of claim 1, wherein said group of at least two different primitive types consists of a line, a stippled line, a circle, and a polygon.

3. The method of claim 1, further comprising:

providing a user interface for a user to input a command for selecting members of said selected class.

4. The method of claim 3, further comprising:

receiving a command from said user interface specifying a display type; and

determining a gamma correction factor appropriate for said display type.

5. The method of claim 1, further comprising:

providing a user interface for a user to disable gamma correction of all members of said group.

6. The method of claim 1, further comprising:

providing a user interface for a user to enable gamma correction of all members of said group.

7. The method of claim 1, wherein said instruction enables gamma correction of one or more types of primitives for a particular scene.

8. A method of forming smoothed primitives in a graphics system having a CPU and a graphics processor, comprising:

receiving a request from a user to selectively enable gamma correction of a selected class of primitive types, said selected class including at least one member selected from a group of at least two different primitive types;

determining a gamma correction factor for said selected class of primitive types;

in said graphics processor, determining a coverage value per pixel for each fragment of a primitive;

in said graphics processor, gamma correcting coverage values of fragments generated for primitives having a primitive type belonging to said selected class of primitives, said gamma correction factor being selected to account for a non-linear response of a display, said graphics processor not performing gamma correction of coverage values for primitives having a primitive type not belonging to said selected class of primitive types; and

in said graphics processor, performing an anti-aliasing process using said gamma corrected coverage values in place of corresponding coverage values.

9. The method of claim 8, wherein said group of at least two different primitive types consists of a line, a stippled line, a circle, and a polygon.

10. The method of claim 8 wherein:

said performing includes blending partially covered pixels with background pixels, with a weight assigned to partially covered pixels being given by the gamma corrected coverage value and a weight assigned to background pixels being one minus the gamma corrected coverage value.

11. The method of claim 8, wherein said anti-aliasing process generates an anti-aliased image, the method further comprising:

in a display, gamma correcting each pixel of said antialiased image.

12. A graphics system, comprising:

a graphics processor, including;

a geometry processor to generate geometric primitives;

a rasterizer to convert geometric primitives into fragments;

a coverage completion module to calculate a coverage value per pixel of a primitive;

a look up table to store a gamma correction factor for gamma correction of a selected class of primitive types, said selected class including at least one member selected from a group of at least two different primitive types; and

said graphics processor performing gamma correction of coverage values of primitives having a primitive type belonging to said selected class of primitive types said graphics processor not performing gamma correction of coverage values for primitives having a primitive type not belonging to said selected class of primitive types.

13. The method of claim 12, wherein said group of at least two different primitive types consists of a line, a stippled line, a circle, and a polygon.

14. The graphics system of claim 12, wherein said gamma correction factor is written into said lookup table in response to a user request.

15. The graphics system of claim 12, further comprising:

a blending processor adapted to blend partially covered pixels with background pixels to achieve sub-pixel resolution of edges of primitives, wherein said blending processor uses said gamma corrected coverage values for coverage values used to anti-alias said primitive.

16. The graphics system of claim 12, wherein said graphics processor is configured to receive said gamma correction factor in response to a user input entered from a graphical user interface.

17. The graphics system of claim 12, further comprising:

a central processing unit having an associated system memory, said central processing unit and said associated system memory coupled to said graphics processor by a bus.

18. The graphics system of claim 17, further comprising:

a user interface for a user input commands to selectively enable gamma correction of two or more different types of primitives.

19. The graphics system of claim 17, further comprising:

a user interface for a user to input commands to enable or disable gamma correction of partially covered primitives.

20. The graphics system of claim 12, wherein said lookup table is run time loadable.