US 6,184,893 B2Granted

Method and system for filtering texture map data for improved image quality in a graphics computer system

AssigneeCirrus Logic, Inc.

InventorsGoran Devic, Christopher W. Shaw

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Abstract

A method and system for filtering texture map data for improved image quality in a graphics computer system. The present invention is directed to a method and system for performing texture map filtering for reducing “flickering” and “sparkling” when rendering a relatively small graphics primitives using a texel map of relatively larger area and low color frequency. A footprint area is defined as the area of texel map space that is mapped into one pixel coordinate of display space. One embodiment of the present invention is particularly useful in texture mapping where the footprint area is larger than one. In this instance, during rendering, the change in texel map coordinates (e.g., du, dv) is large for a unit change in screen coordinates (e.g., dx, dy). When obtaining a texel at location (u, v), the present invention performs a color filtering of texels located at distances du and dv away from the texel at location (u, v). If texel wrap is not allowed, edge pinning is used to obtain the required texels for color filtering. The texels which are rendered in adjacent pixels on the display screen become more colored filtered with respect to each other rather than filtering nearest neighbor texels which often leads to flickering and sparkling in texture mapping cases of large footprint areas. The present invention reduces flickering and sparkling without requiring multiple texture maps (and therefore additional memory), as required using mipmapping.

Claims21

Dependent claims

In a computer controlled graphics display system, a method of performing texture mapping for a graphics primitive comprising the steps of:

a) determining a set of pixels within said graphics primitive;
b) texture mapping each respective pixel of said set of pixels based on a texture map wherein said each respective pixel has an x-coordinate and a v-coordinate, said step b) comprising the steps of:
b1) receiving a first sample distance, du, along a first texel dimension, u, wherein said first sample distance, du, is derived and Proportionally based on a change, dx, in the x-coordinate of a respective pixel and wherein the chance, dx, is derived from a difference between a previous value of the x-coordinate from a previously displayed image of said graphics primitive and a current value of the x-coordinate from a currently displayed image of said graphics primitive;
b2) receiving a second sample distance, dv, along a second texel dimension, v, wherein said second sample distance, dv, is derived and proportionally based on a change, dv, in the v-coordinate of said respective pixel and wherein the change, dv, is derived from a difference between a previous value of the y-coordinate from a previously displayed image of said graphics primitive and a current value of the y-coordinate from a currently displayed image of said graphics primitive;
b3) receiving a coordinate (u, v) of a sample texel corresponding to said respective pixel;
b4) determining colors of a set of texels within said texture map determinedly located at said first and second sample distances away from said coordinate of said sample texel;
and
b5) color averaging said colors determined at step b4) with a color of said sample texel to obtain a texel component for said respective pixel for a subsequently displayed image of said graphics primitive;
and
c) displaying said set of pixels with respective texel components.

7 more elements

In a computer controlled graphics display system, a method of performing texture mapping for a polygon, stored in a display list, said method comprising the steps of:

a) determining a set of pixels within said polygon;
b) texture mapping each respective pixel of said set of pixels based on a texture map wherein said each respective pixel has an x-coordinate and a y-coordinate, said step b) comprising the steps of:
b1) receiving a first sample distance, du, along a first texel dimension, u, wherein said first sample distance, du, is derived and proportionally based on a change, dx, in the x-coordinate of a respective pixel and wherein the chance, dx, is derived from a difference between a previous value of the x-coordinate from a previously displayed image of said polygon and a current value of the x-coordinate from a currently displayed image of said polygon;
b2) receiving a second sample distance, dv, along a second texel dimension, v, wherein said second sample distance, dv, is derived and proportionally based on a change, dy, in the y-coordinate of said respective pixel and wherein the change, dy, is derived from a difference between a previous value of the y-coordinate from a previously displayed image of said polygon and a current value of the y-coordinate from a currently displayed image of said polygon;
b3) receiving a coordinate (u, v) of a sample texel corresponding to said respective pixel;
b4) determining colors of a set of texels within said texture map determinedly located at (u, v+dv), (u, v−dv), (u+du, v) and (u−du, v) coordinates;
and
b5) color averaging texel colors determined at step b4) with a color of said sample texel to obtain a texel component for said respective pixel for a subsequently displayed image of said polygon;
and
c) displaying said set of pixels with respective texel components.

7 more elements

A computer controlled graphics display system comprising:

a processor coupled to a bus;
a computer readable memory system coupled to the bus;
a rasterization circuit for determining a set of pixels within a graphics primitive stored in said memory system wherein each respective pixel of said set of pixels has an x-coordinate and a y-coordinate;
a parameterization circuit for determining and supplying a first sample distance, du, along a first texel dimension of a texel map and a second sample distance, dv, along a second texel dimension of said texel map wherein said first sample distance, du, is derived and proportionally based on a change, dx, in the x-coordinate of a respective pixel in which the change, dx, is derived from a difference between a previous value of the x-coordinate from a previously displayed image of said graphics primitive and a current value of the x-coordinate from a currently displayed image of said graphics primitive and wherein said second sample distance, dv, is derived and proportionally based on a chance, dy, in the y-coordinate of said respective pixel in which the change, dv, is derived from a difference between a previous value of the y-coordinate from a previously displayed image of said graphics primitive and a current value of the y-coordinate from a currently displayed image of said graphics primitive;
texture circuitry for texel mapping each respective pixel of said set of pixels, said texture circuitry for receiving a coordinate (u, v) of a sample texel, for determining colors of a set of texels within said texel map determinedly located at said first and second sample distances away from said coordinate of said sample texel, for color averaging said colors with a color of said sample texel to obtain a texel component for said respective pixel for a subsequently displayed image of said graphics primitive;
and
a display screen for displaying said set of pixels with respective texel components.

4 more elements

Dependencies are inferred from the claim text.