Antialiased imaging with improved pixel supersampling

• US 6,072,500 A
• Filed: 09/17/1997
• Issued: 06/06/2000
• Est. Priority Date: 07/09/1993
• Status: Expired due to Term

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Silicon Graphics Incorporated (Graphics Properties Holdings, Inc.)
• Inventors: Leather, Mark M., Foran, James L.
• Primary Examiner(s): Zimmerman, Mark K.
• Application Number:
  US08/932,371
• Time in Patent Office: 993 Days
• Field of Search: 345/422, 345/426, 345/431, 345/432, 345/136, 345/138
• US Class Current: 345/611
• CPC Class Codes: G06T 11/001 Texturing; Colouring; Generation of texture or colour inpainting G06T5/77
• CPC Class Codes: G06T 11/40 Filling a planar surface by adding surface attributes, e.g. colour or texture
• CPC Class Codes: G06T 15/503 Blending, e.g. for anti-aliasing
• CPC Class Codes: G06T 2200/12 involving antialiasing

Abstract

An image processing system is described that receives polygonal image data at the direction of a processor and develops antialiased image data for display on a raster scanned display. In particular, the image system includes a scan convertor for converting the polygonal image data into pixel data, which includes pixel screen coordinates and at least one color value for each polygon covered pixel of the pixel data and a supersample coverage mask indicating an extent of polygon coverage within each polygon covered pixel. The image system also includes a raster system having at least one image processor for receiving the pixel data for each pixel, for developing a region mask based on the supersample coverage mask, and for storing the color value in association with the region mask as anitialiased display data in an image memory in communication with the image processor based on the pixel screen coordinates. The region mask indicates one or more, geographical regions of supersamples within each pixel covered by one or more polygons and indicates a color value stored in the image memory to be assigned to the supersamples in a region. This requires only a single color value for supersamples within a region of a covered pixel to be stored in the image memory. The image system can also be configured to develop and store Z-values, alpha values, stencil values, and texture values for each pixel for storage in the image memory in association with the region mask.

Claims

1. A raster system for generating antialiased display data within an image processing system, wherein said image processing system includes a scan conversion subsystem for generating pixel packets which indicate polygon coverage within a pixel, wherein the pixel comprises a plurality of supersamples, comprising:

a first image memory for storing a first color value;

a second image memory for storing a second color value;

means for storing pixel memory that indicates a current state of the pixel, wherein said pixel memory comprises a region mask having a plurality of fields, each field being associated with a unique one of said plurality of supersamples, wherein when the color value of each supersample is either said first color value or said second color value, then each field associated with a supersample having said first color value stores an identifier that identifies said first image memory, and each field associated with a supersample having said second color value stores an identifier that identifies said second image memory; and

an image processor, coupled to receive a pixel packet from the scan conversion subsystem, and further coupled to update said pixel memory, wherein said image processor generates antialiased display data based on said pixel memory, and wherein said image processor includes,

means for determining a new pixel state based on said current state of the pixel and said pixel packet, and

means for updating said pixel memory based on said new pixel state.

2. The raster system of claim 1, wherein said pixel memory further comprises a mode identifier, wherein said region mask and said mode identifier together indicate said current state of the pixel.

3. The raster system of claim 2, wherein said pixel packet comprises a supersample coverage mask.

4. The raster system of claim 3, wherein said pixel memory further comprises a plurality of supersample memories, each of said supersample memories including a color value field that stores a color value.

5. The raster system of claim 4, wherein said means for updating updates said color value field of each supersample memory only when the pixel is associated with more than two colors.

6. The raster system of claim 5, wherein each of said plurality of supersample memories further includes a Z-value field that stores a Z-value, and said pixel packet further comprises at least one Z-value.

7. The raster system of claim 6, wherein said means for updating performs Z-buffering on a supersample-by-supersample basis.

8. The raster system of claim 1, wherein said pixel memory indicates a current pixel state according to a rendering mode.

9. The raster system of claim 8, wherein said rendering mode comprises a blended polygon rendering mode and a non-blended polygon rendering mode.

10. The raster system of claim 1, wherein each of said fields of said region mask consists of a single binary digit that can hold one of two values:

0 or 1.

11. A method for generating antialiased display data comprising:

(1) storing a pixel memory that indicates a current state of a pixel that comprises a plurality of supersamples, wherein said pixel memory comprises a region mask having a plurality of fields, each field being associated with a unique one of said supersamples;

(2) receiving a pixel packet, wherein said pixel packet indicates polygon coverage within said pixel, and a first color value;

(3) storing a second color value in an image memory, wherein said second color value is a function of said first color value;

(4) determining a new pixel state based on said current pixel state and said pixel packet;

(5) updating said pixel memory based on said new pixel state, wherein if said new pixel state is a state in which the color value of each supersample is either said second color value or a third color value, each of the fields associated with a supersample having said second color value stores an identifier that identifies said image memory; and

(6) generating antialiased display data based on said pixel memory.

12. The method of claim 11, wherein said pixel memory further comprises a mode identifier, wherein said region mask and said mode identifier together indicate said current state of said pixel.

13. The method of claim 12, wherein said pixel packet comprises a supersample coverage mask.

14. The method of claim 13, wherein said pixel memory further comprises a plurality of supersample memories, each of said supersample memories including a color value field that stores a color value.

15. The method of claim 14, wherein said color value field of each of said supersample memories is updated in step (5) only when said pixel is associated with more than two colors.

16. The method of claim 15, wherein each of said plurality of supersample memories further includes a Z-value field that stores a Z-value, and said pixel packet further comprises at least one Z-value.

17. The method of claim 16, wherein said step of updating comprises Z-buffering on a supersample-by-supersample basis.

18. The method of claim 11, wherein said second color value equals said first color value.

19. The method of claim 11, wherein said second color value is a function of not only said first color value, but also the color value stored in said image memory prior to said second color value being stored in said image memory.

20. A computer graphics system comprising:

a host processor, wherein said host processor generates world coordinate based graphical data;

a geometry subsystem, coupled to receive said world coordinate based graphical data, wherein said geometry subsystem converts said world coordinate based graphical data to screen space coordinate data;

a scan conversion subsystem, coupled to receive said screen space coordinate data, wherein said scan conversion subsystem generates pixel packets based on said screen space coordinate data;

a raster system including,

a first image memory for storing a first color value;

a second image memory for storing a second color value;

means for storing a pixel memory corresponding to a pixel comprising a plurality of supersamples, said pixel memory indicating a current state of said pixel and comprising a region mask having a plurality of fields, each field being associated with a unique one of said supersamples, wherein when the color value of each supersample is either said first color value or said second color value, then each field associated with a supersample having said first color value stores an identifier that identifies said first image memory, and each field associated with a supersample having said second color value stores an identifier that identifies said second image memory, and

an image processor, coupled to receive a pixel packet from the scan conversion subsystem, and further coupled to update said pixel memory, wherein said image processor generates antialiased display data based on said pixel memory, and wherein said image processor includes,

means for determining a new pixel state based on said current pixel state and said pixel packet, and

means for updating said pixel memory based on said new pixel state; and

a display subsystem, coupled to receive said antialiased display data.

21. A method, comprising the steps of:

initializing a region mask that is used to indicate a state of a pixel comprising a plurality of supersamples, wherein said region mask comprises a plurality of fields equal in number to said plurality of supersamples, wherein each of said plurality of fields is associated with a unique one of said supersamples;

generating a first coverage mask associated with said pixel and with a first polygon image having a color, wherein said first coverage mask indicates the supersamples covered by said first polygon image;

storing a first color value in a first image memory, wherein said first color value is a function of at least said color of said first polygon image;

updating said region mask based on said first coverage mask, wherein after said region mask is updated said region mask contains data identifying said supersamples covered by said first polygon image;

generating a second coverage mask associated with said pixel and with a second polygon image having a color, wherein said second coverage mask identifies the supersamples covered by said second polygon image;

storing a second color value in a second image memory, wherein said second color value is a function of at least said color of said second polygon image; and

updating said region mask based on said second coverage mask, wherein after said region mask is updated said region mask associates a first group of said supersamples with said first color value and associates a second group of said supersamples with said second color value.

22. The method of claim 21, further comprising the step of associating each of said plurality of supersamples with a supersample memory comprising a color field that stores a color value.

23. The method of claim 22, further comprising the step of storing a color value in each color field only if more than two colors are associated with said pixel.

24. The method of claim 21, wherein each of said fields consists of a single binary digit that can hold one of two values:

0 or 1.

25. The method of claim 21, further comprising the step of initializing a mode identifier, wherein said mode identifier together with said region mask indicates said state of said pixel.