Cirrus Logic Inc.

Nvidia Corporation

S3 Incorporated, Inc.

Daniel P Wilde

Gautam P Vaswani

Steven E Molnar

Mark J French

Thomas A Dye

Michael K Larson

Robert J Stoll

Bengt-Olaf Schneider

Jerome Francis Duluk, Jr

Henry Packard Moreton

John Stephen Montrym

Shirish C Gadre

Christian Rouet

Manan Patel

Jonathan J Dunaisky

Patrick A Harkin

Timothy J McDonald

Weizhong Xu

Tom A Dye

A system, method, and computer program product are provided for discarding pixel samples. The method includes the steps of completing shading operations for a pixel set including one or more pixels to generate per-sample shaded attributes according to a shader program executed by a processing pipeline. Discard information for the pixel set is evaluated and one or more per-sample shaded attributes for at least one pixel in the pixel set are discarded based on the evaluated discard information.

System, method, and computer program product for discarding pixel samples

One embodiment of the present invention sets forth a technique for improving graphics rendering efficiency by processing pixels in a compressed format whenever possible within a multi-sampling graphics pipeline. Each geometric primitive is rasterized into fragments, corresponding to screen space pixels covered at least partially by the geometric primitive. Fragment coverage represents the pixel area covered by the geometric primitive and determines the weighted contribution of a fragment color to the corresponding screen space pixel. Samples associated with a given fragment are called sibling samples and have the same color value. The property of sibling samples having the same color value is exploited to compress and process multiple samples, thereby reducing the size of the associated logic and the amount of data written to and read from the frame buffer.

Color-compression using automatic reduction of multi-sampled pixels

A technique for handling floating-point special values, e.g., Infinity, NaN, &#x2212;Zero, and denorms, during blend operations is provided so that blend operations on fragment color values that contain special values can be performed in compliance with special value handling rules. In particular, the presence of special values is detected or the potential presence of special values is detected. This information is used to qualify when blend optimizations may be performed, so that floating point blend operations can remain conformant to special value handling rules.

Blend optimizations that are conformant to floating-point rules

States that are used in configuring a processing pipeline are passed down through a separate pipeline in parallel with the data transmitted down through the processing pipeline. With this separate pipeline, the states for configuring any one stage of the processing pipeline are continuously available in the corresponding stage of the state pipeline, and new states for configuring the processing pipeline can be transmitted down the state pipeline without flushing the processing pipeline. The processing pipeline and the separate pipeline for the states can be divided into multiple sections so that the width of the separate pipeline for the states can be reduced.

System and method for storing states used to configure a processing pipeline in a graphics processing unit

A z buffer stores compressed z data represented in a planar format for one or more tiles. The compressed format includes a set of tile specific coefficients defining a plane equation for each z tested primitive intersecting the tile. The z buffer stores a maximum number of sets of tile specific coefficients for each tile, and when the maximum number of sets is exceeded for a particular tile, an uncompressed format is used to store the z data for the particular tile.

Planar z representation for z compression

A software graphics engine includes a selectable mode filter for improved texture mapping. An x, y pixel coordinate is mapped into a u, v texture map. The mapped u, v coordinate includes integer and fractional portions. Depending on the location of the coordinate relative to the four nearest texels, which are represented as integers, one of several texture mapping schemes are used to either select or calculate the texel value to be used to render the pixel at the x, y screen location. The three texture mapping schemes include point sampling in which the nearest texel from the texture map is selected, two-texel averaging in which the closest two texels are combined in a weighted average, and four-texel averaging in which the closest four texels are combined in a weighted average. By providing a selectable filter than can perform point sampling or two or four-texel averaging, the speed benefit of point sampling can be approached as well as the superior quality of two- and four-texel averaging.

Dynamically selectable texture filter for a software graphics engine

A graphics system includes a graphics controller for rendering polygons with texture using an improved MIP mapping technique. The graphics controller includes a polygon engine for rendering the pixels in a polygon and a texture map engine for selecting texture elements (&ldquo;texels&rdquo;) from an appropriate texture map to be applied to the pixels rendered by the polygon engine. The texture map engine generates texel coordinate values from pixel coordinate values provided by the polygon engine. The appropriate texture map is selected from a set of texture maps each varying from the others by the level of detail of the texture in each map. The graphics controller selects the appropriate level of detail texture map to use to increase speed, efficiency, and realism quality of the graphics system. The determination as to which level of detail texture map is appropriate is made by computing the area bounded by adjacent texel coordinates generated by the texture map engine. In one embodiment, vectors are defined for each the adjacent texels and the area is determined from the magnitude of the cross product of the vectors. An embodiment of the invention includes software for calculating the area bounded by adjacent texel coordinates and for comparing the area to a range of values. The software also selects an appropriate texture map based on the results of the comparison.

Auto level of detail texture mapping for a software graphics engine

Graphics software renders polygons with texture using an improved MIP mapping technique in which texels from multiple MIP maps are blended together. The software renders the pixels in a polygon and selects texture elements (&ldquo;texels&rdquo;) from an appropriate texture map to be applied to the pixels. The software further generates texel coordinate values to select texel values from a set of texture maps, each map varying from the others by the level of detail of the texture. The software then computes a scale factor for each texel value according an area bounded by adjacent texel coordinates. In one embodiment, vectors are defined for each the adjacent texels and the area is determined from the magnitude of the cross product of the vectors. The scale factor is then used to compute a weighted average of texels from one or more MIP maps. Further, for certain area values, no averaging occurs or, alternatively, the scale factor is set to 1.0.

Dynamically selectable MIP map blending for a software graphics engine

A graphics processor capable of rendering three-dimensional polygons with color, shading; and other visual effects also corrects interpolation errors that occur as a result of mapping the polygon to a pixel grid display. The processor renders polygons using an Incremental Line-Drawing algorithm and features an error correction circuit capable of adjusting the initial and incremental gradient parameters for each pixel characteristic and then rendering each scan line with the proper orthogonal adjustment. The error correction circuit includes an ortho correction engine for correcting errors in the initial and incremental pixel parameters and an ortho adjust engine to accommodate overflows in the x-coordinate calculations. The processor is able to render the polygons with monotonic gradients in color, shading, depth, and other visual characteristics without interpolation error.

Error correction in a graphics processor

A method for dynamically caching display list information to an internal on-chip cache performs UV title read hit comparisons to determine whether to read display list parameters from internal cache or external memory.

Method for dynamic XY tiled texture caching

A graphics system includes a graphics controller for rendering polygons with texture using an improved MIP mapping technique in which texels from multiple MIP maps are blended together. The graphics controller includes a polygon engine for rendering the pixels in a polygon and at texture map engine for selecting texture elements ('texels') from an appropriate texture map to be applied to the pixels rendered by the polygon engine. The texture map engine generates texel coordinate values from pixel coordinate values provided by the polygon engine. Texel values are selected from a set of texture maps each map varying from the others by the level of detail of the texture in each map. The graphics controller computes a scale factor for each texel value according an are a bounded by adjacent texel coordinates generated by the texture map engine. The scale factor is then used to compute a weighted average of texels form more than one MIP maps. In the preferred embodiment, vectors are defined for each the adjacent texels and the area is determined from the magnitude of the cross product of the vectors.

MIP map blending in a graphics processor

A graphics system including a selectable mode filter for improved texture mapping. An x, y pixel coordinate is mapped into a u, v texture map. The mapped u, v coordinate includes integer and fractional portions. Depending on the location of the coordinate relative to the four nearest texels, which are represented as integers, one of several texture mapping schemes are used to either select or calculate the texel value to be used to render the pixel at the x, y screen location. The three texture mapping schemes include point sampling in which the nearest texel from the texture map is selected, two-texel averaging in which the closest two texels are combined in a weighted average, and four-texel averaging in which the closest four texels are combined in a weighted average. By providing a selectable filter than can perform point sampling or two or four-texel averaging, the speed benefit of point sampling can be approached as well as the superior quality of two and four-texel averaging.

Dynamically selectable texture filter for computer graphics

An improved method and apparatus for rendering curved surfaces in a graphics system. The appearance of a curved surface is created by varying color shades across an object. The graphics systems represents each primary color with fewer than eight bits. The present invention maintains smooth transaction between color shades despite using fewer than eight bits to represent color. An eight bit color shade value is truncated, with the most significant bits being saved and used as a color value. The least significant bits that are truncated are used to determine which of the adjacent color values to use to render pixels. Thus, if five bits are saved and used to represent a color, the three least significant truncated bits are used to determine the appropriate mix of the closest five bit shades. The three truncated bits are used to select an entry from a ramp table and a control signal from a look-up table selects a bit from the selected ramp table entry. The selected bit is used to determine which of the closest five bit shades to use for rendering a pixel.

Dithering method and apparatus using ramp probability logic

A texture value determining (TVD) circuit approximates non-homogenous 2nd order perspective texture mapping to provide texture for a polygon using linear interpolation and input parameters. The TVD circuit of the present invention includes a vertical walk subcircuit and an orthogonal walk subcircuit. The vertical walk subcircuit determines texture coordinates, u(a.sub.0,n) and v(a.sub.0,n) that represent the pixels along a vertical main slop of a triangle polygon. The orthogonal walk subcircuit determines texture coordinates, u(a.sub.m,n) and v(a.sub.m,n), for orthogonally walked polygon coordinate positions for which m&gt;0. The orthogonally walked coordinate positions represent individual scan lines. The vertical walk subcircuit of the TVD circuit includes adders, latches, and accumulators. Each element of the vertical walk subcircuit receives a vertical main slope clock (n-clock) signal. An output of the vertical walk subsystem is computed based on the relationship,

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Cedar Park, TX, United States of America

Daniel P Wilde