Method and apparatus for providing polygon pixel sub-sample information using incremental means

In a graphics system capable of rendering a primitive, an edge stepper for generating coordinate data for display pixels on a display device that represent the primitive, the edge stepper receiving edge equation data including a first and second pair of endpoint coordinates and a slope value for at least one edge of the primitive to be rendered, the edge stepper comprising:

• an adder, for incrementing one of the first endpoint coordinates by an increment value to provide an edge x and an edge y coordinate of the at least one edge of the primitive being rendered, wherein the increment value is less than a size of a display pixel in one mode of operation.

A graphics device for displaying an image on a display device based on data received from a host processor, the display device comprising a plurality of scan lines, each of the scan lines comprising a plurality of pixels, the graphics device comprising:

• a graphics accelerator, coupled to receive data from the host processor representing a plurality of graphics primitives, the graphics accelerator generating edge equations for each primitive, the edge equations including, for at least one edge of the primitive, endpoint coordinate data identifying endpoints of the at least one edge of the primitive and slope data identifying a rate of change of the at least one edge;
• a scan converter, coupled to the graphics accelerator, that translates the edge equations into coordinates of pixels of the display device, the scan converter including an edge stepper to step from one of the coordinates of one of the endpoints of the at least one edge to another endpoint of the at least one edge to generate pixel coordinates for the edge, wherein a size of step of the edge stepper is less than a size of a display pixel.

A method of simplifying a mathematical calculation in an antialiasing operation for antialiasing an image displayed on a display screen, the mathematical calculation operating on at least one piece of information relating to the image, the information having an integer component and a fractional component, the method including steps of:

• scaling the image by an amount such that the at least one piece of information has only an integer component and does not have a fractional component;
• and
• performing the mathematical calculation during the antialiasing operation based on the at least one piece of information that has only an integer component.

A method of simplifying a mathematical calculation in an antialiasing operation for antialiasing an image displayed on a display screen, the mathematical calculation operating on at least one piece of information relating to the image, the information having an integer component and a fractional component, the method including a step of:

• scaling the image by an amount such that the at least one piece of information operated upon by the mathematical calculation during the antialiasing operation has only an integer component and does not have a fractional component;
• wherein the method of simplifying a mathematical calculation is employed in a multi-point sampling anti-aliasing operation, wherein the display screen includes a plurality of pixels and wherein the at least one piece of information relating to the image comprises at least one subsample point for each of the plurality of pixels, the at least one subsample point lying on a non-integer pixel boundary of the display screen, wherein the step of scaling provides a scaled representation of the image in which each of the plurality of subsamples falls on an integer address boundary of the display screen.