Apparatus and method for fragment operations in a 3D-graphics pipeline

A method for rendering a graphics image, said method comprising:

• performing one of the following fragment operations on a fragment on a per-pixel basis:
• scissor test, stipple test, alpha test, color test;
• programmatically selecting, based on a state parameter, whether to perform a stencil test on a per-pixel or a per-sample basis, and
• performing said stencil test on said selected basis;
• and
• programmatically selecting a set of subdivisions of a pixel as samples for use in a fragment operation on a per-sample basis;
• programmatically assigning different weights to two samples in said set;
• and
• performing one of the following fragment operations on a per-sample basis, using said programmatically selected and differently weighted samples:
• Z test, blending, dithering;
• then programmatically selecting a different set of subdivisions of a pixel as samples for use in a second fragment operation on a per-sample basis;
• and
• then performing said second fragment operation on a fragment on a per-sample basis, using said programmatically selected samples.

A computer-readable medium for data storage wherein is located a computer program for causing a graphics-rendering system to render an image by:

• performing one of the following fragment operations on a fragment on a per-pixel basis:
• scissor test, stipple test, alpha test, color test;
• programmatically selecting, based on a state parameter, whether to perform a stencil test on a per-pixel or a per-sample basis, and
• performing said stencil test on said selected basis;
• and
• programmatically selecting a set of subdivisions of a pixel as samples for use in a fragment operation on a per-sample basis,
• performing one of the following fragment operations on a per-sample basis, using said programmatically selected samples:
• Z test, blending, dithering;
• then programmatically selecting a different set of subdivisions of a pixel as samples for use in a second fragment operation on a per-sample basis;
• and
• then performing said second fragment operation on a fragment on a per-sample basis, using said programmatically selected samples.

A system for rendering graphics images, said system comprising:

• a port for receiving commands from a graphics application;
• an output for sending a rendered image to a display;
• and
• a fragment-operations pipeline, coupled to said port and to said output, said fragment-operations pipeline comprising:
• a stage for performing a fragment operation on a fragment on a per-pixel basis based on data having per-pixel resolution;
• and
• a stage for performing a fragment operation on said fragment on a per-sample basis based on data having per-sample resolution wherein said per-sample resolution is different than said per-pixel resolution.

A graphics rendering method for forming a rendered image in a frame buffer, the graphics rendering method comprising the steps:

• receiving graphics data comprising graphics primitives;
• spatially sorting the received graphics primitives into a plurality of tiles, each tile comprising a muliplicity of pixel locations within the image;
• selecting a current tile from the plurality of tiles;
• generating primitive fragments of the graphics primitives in the current tile;
• reading previously stored per-pixel color data from the frame buffer;
• converting the read per-pixel color data into per-sample color data;
• storing the per-sample color data in a sample buffer, wherein said sample buffer is separate from said frame buffer;
• performing per-sample fragment operations on the primitive fragments and the stored per-sample color data, generating updated per-sample color data, the updated per-sample color data being stored in the sample buffer;
• converting the per-sample color data in the sample buffer into updated per-pixel color data;
• and
• storing the updated per-pixel color data into the frame buffer.

A graphics rendering method for forming a rendered image in a frame buffer, the graphics rendering method comprising the steps:

• receiving graphics data comprising graphics primitives;
• spatially sorting the received graphics primitives into a plurality of tiles, each tile comprising a multiplicity of pixel locations within the image;
• selecting a current tile from the plurality of tiles;
• generating primitive fragments of the graphics primitives in the current tile;
• performing per-sample fragment operations on the primitive, generating per-sample color data;
• storing the generated per-sample color data in one of a plurality of sample buffers;
• converting the stored per-sample color data into per-pixel color data;
• storing the per-pixel color data, and not the per-sample color data, into one of a plurality of pixel tile buffers;
• and.
• transferring the per-pixel color data from the one of a plurality of pixel tile buffer to the frame buffer.

A graphics pipeline forming a rendered image in a frame buffer, the graphics pipeline comprising:

• logic receiving graphics data comprising graphics primitives;
• logic spatially sorting the received graphics primitives into a plurality of tiles, each tile comprising a multiplicity of pixel locations within the image;
• a first memory storing the sorted graphics primitives;
• logic selecting a current tile from the plurality of tiles;
• logic generating primitive fragments of the graphics primitives in the current tile;
• read logic reading previously stored per-pixel color data for the current tile from the frame buffer;
• a second memory storing the per-pixel color for the current tile;
• logic converting the per-pixel color data in the second memory into per-sample color data;
• a third memory storing the per-sample color data;
• fragment logic comprising logic performing per-sample fragment operations on the primitive fragments and the stored per-sample color data, generating updated per-sample color data, the updated per-sample color data being stored in the third memory;
• logic converting the per-sample color data in the third memory into updated per-pixel color data;
• and
• logic storing the updated per-pixel color data into the frame buffer.

A graphics pipeline forming a rendered image in a frame buffer, the graphics pipeline comprising:

• logic receiving graphics data comprising graphics primitives;
• logic spatially sorting the received graphics primitives into a plurality of tiles, each tile comprising a multiplicity of pixel locations within the image;
• a first memory storing the sorted graphics primitives;
• logic selecting a current tile from the plurality of tiles;
• logic generating primitive fragments of the graphics primitives in the current tile;
• a plurality of second memories storing per-sample color data;
• fragment logic performing per-sample fragment operations on the primitive fragments and generating per-sample color data, storing the per-sample color data in a selected one of the second memories;
• a plurality of third memories storing per-pixel color values, and not per-sample color values;
• logic converting the per-sample color data in the selected second memory into per-pixel color data, storing the per-pixel color data, and not per-sample color data, into a selected one of the third memories;
• and
• logic storing the per-pixel color data into the frame buffer.

A computer-readable medium for data storage wherein is located a computer program for causing a graphics-rendering system to render an image by:

• receiving first data associated with a fragment having pixel-level resolution;
• performing a first fragment operation on said fragment on a per-pixel basis using said first data;
• receiving second data associated with said fragment having sample-level resolution wherein said per-sample resolution is different than said per-pixel resolution;
• and
• performing a second fragment operation on said fragment on a per-sample basis using said second data.