Apparatus and method for managing graphic attributes in a memory cache of a programmable hierarchical interactive graphics system

• US 5,914,726 A
• Filed: 06/27/1997
• Issued: 06/22/1999
• Est. Priority Date: 06/27/1997
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Schultz, Karl W.
• Primary Examiner(s): Tung, Kee M.
• Assistant Examiner(s): Luu, Sy D.
• Application Number:
  US08/883,679
• Time in Patent Office: 725 Days
• Field of Search: 345/508, 345/429-433, 345/501, 707/104
• US Class Current: 345/501
• CPC Class Codes: G06T 1/60 Memory management

Abstract

A method and apparatus for processing graphics information in an attribute-type pipelined graphics system, such as a Programmable Hierarchical Interactive Graphics System (PHIGS). In accordance with the broad aspects of the invention, the method includes the step of reading a program segment defining various graphic primitives to be drawn, wherein the appearance of the primitives are defined, in part, by graphic attributes. After reading the program segment, the method further includes a step of identifying graphic attributes in the program segment, and indexing each attribute into a unique attribute segment of an attribute cache. Finally, the method includes the step of processing each primitive by accessing only those attributes that affect the rendering of the primitive being processed, and transmitting only those attributes that accessed to the graphics pipeline. Advantageously, this reduces the number of total attributes that are sent to the graphics pipeline and processed thereby.

Claims

1. An apparatus for processing graphics information in a programmable hierarchical interactive graphics system (PHIGS) comprising:

a first computer readable storage medium containing a PHIGS data structure, the PHIGS data structure including a plurality of ordered elements that define one or more graphics primitives;

a second computer readable storage medium defining an array of attribute cache segments, wherein each segment is uniquely dedicated to a distinct attribute type; and

a processing element for processing the elements in the PHIGS structure, the processing element further including;

an attribute indexer configured to sequentially evaluate each of the ordered elements to identify each attribute and uniquely index each attribute into the segment of the second computer readable storage medium that is dedicated for that particular attribute type;

a command identifier configured to identify a directive for a graphics system to display a graphic primitive; and

a primitive analyzer, responsive to the command identifier, configured to communicate to a geometry accelerator only those attributes in the second computer readable storage medium that effect the rendering of a particular graphic primitive, identified by the command identifier.

2. The apparatus as defined in claim 1, wherein the plurality of elements in the PHIGS structure includes one or more graphic primitives and one or more graphic primitive attributes.

3. The apparatus as defined in claim 1, wherein the second computer readable storage medium defines a plurality of attribute segments, wherein each attribute segment has a defined relationship to a unique attribute, the attribute segments including at least one from the group consisting of:

line color, line type, line width, surface color, text color, text path, text font, text precision, character spacing, and fill area attributes including, empty, hollow, pattern, hatch, and solid.

4. The apparatus as defined in claim 1, further including a cache write segment responsive to the attribute indexer to overwrite data existing in a particular attribute segment, with new attribute segment data.

5. The apparatus as defined in claim 4, wherein the cache write segment is configured to write a pointer value into the particular attribute segment, wherein the pointer points to a particular location in the PHIGS data structure.

6. The apparatus as defined in claim 1, wherein the primitive analyzer is configured to analyze an op code of a particular graphic primitive to ascertain the relevant attribute segments to process for the particular graphic primitive.

7. The apparatus as defined in claim 1, wherein the primitive analyzer is configured to analyze an op code of a particular graphic attribute to identify the particular attribute segment that the graphic attribute is indexed to.

8. An apparatus for processing graphics information in a programmable hierarchical interactive graphics system (PHIGS) comprising:

a first computer readable storage medium containing a PHIGS data structure, the PHIGS data structure including a plurality of elements that define one or more graphics primitives;

a second computer readable storage medium defining an array of attribute cache segments, wherein each segment is uniquely dedicated to a distinct attribute type; and

processing means for processing the elements in the PHIGS structure, the processing means further including;

indexing means for identifying attributes in the first computer readable storage medium, and uniquely indexing the attributes into segments of the second computer readable storage medium that are dedicated for the particular identified attributes;

identifying means for identifying a directive for a graphics system to display a graphic primitive; and

analyzer means, responsive to the identifying means, for communicating to a geometry accelerator only those attributes in the second computer readable storage medium that effect the rendering of the particular graphic primitive identified by the identifying means.

9. The apparatus as defined in claim 8, wherein the plurality of elements in the PHIGS structure includes one or more graphic primitives and one or more graphic primitive attributes.

10. The apparatus as defined in claim 8, wherein the second computer readable storage medium defines a plurality of attribute segments, wherein each attribute segment has a defined relationship to a unique attribute, the attribute segments including at least one from the group consisting of:

line color, line type, line width, surface color, text color, text path, text font, text precision, character spacing, and fill area attributes including, empty, hollow, pattern, hatch, and solid.

11. The apparatus as defined in claim 8, further including a cache write means responsive to the indexing means for overwriting data existing in a particular attribute segment, with new attribute segment data.

12. The apparatus as defined in claim 11, wherein the cache write means includes means for writing a pointer value into the particular attribute segment, wherein the pointer points to a particular location in the PHIGS data structure.

13. The apparatus as defined in claim 8, wherein the analyzer means further includes means for analyzing an op code of a particular graphic primitive to ascertain the relevant attribute segments to process for the particular graphic primitive.

14. The apparatus as defined in claim 8, wherein the analyzer means further includes means for analyzing an op code of a particular graphic attribute to identify the particular attribute segment that the graphic attribute is indexed to.

15. A method for processing graphics information in a programmable hierarchical interactive graphics system (PHIGS) comprising the steps of:

reading a program segment defining a PHIGS data structure, the PHIGS data structure including both graphic attributes and directives for drawing graphic primitives;

identifying graphic attributes in the PHIGS data structure;

successively evaluating each element in the PHIGS data structure and indexing each attribute type into a unique attribute segment of an attribute cache, until reaching a directive for drawing a graphic primitive; and

communicating to a geometry accelerator for processing the graphic primitive only those attributes that effect the rendering of the primitive being processed.

16. The method as defined in claim 15, further including the initial step of clearing all attribute locations and assuming a predetermined attribute state.

17. The method as defined in claim 15, wherein the step of indexing each attribute further includes the step of examining an op code of the graphic attributes.

18. The method as defined in claim 15, wherein the step of processing each primitive further includes the step of accessing a memory area that associates particular attributes with a given graphic primitive.

19. An apparatus for processing graphics information in a programmable hierarchical interactive graphics system (PHIGS) comprising:

a first computer readable storage medium containing a PHIGS data structure, the PHIGS data structure including a plurality of ordered elements that define one or more graphics primitives;

a second computer readable storage medium defining an array of attribute cache segments, wherein each segment is uniquely dedicated to a distinct attribute type;

a third computer readable storage medium defining an array of attribute cache segments, wherein each segment is uniquely dedicated to a distinct attribute type; and

a processing element for processing the elements in the PHIGS structure, the processing element further including;

an attribute indexer configured to sequentially evaluate each of the ordered elements to identify each attribute and uniquely index each attribute into the segment of the second computer readable storage medium that is dedicated for that particular attribute type;

a command identifier configured to identify a directive for a graphics system to display a graphic primitive;

means, responsive to the command identifier, for communicating the contents of the second computer readable storage medium to a geometry accelerator for displaying the graphic primitive;

means for copying contents of the second computer readable storage medium into the third computer readable storage medium; and

means for clearing the contents of the second computer readable storage medium.

20. The system as defined in claim 19, further including means for transferring attribute values from the second computer readable storage medium into the third computer readable storage medium.

21. The system as defined in claim 19, wherein the third computer readable storage medium is constructed from the same physical memory as the second computer readable storage medium, but is logically constructed as a separate array of elements.