Imagination Technologies Limited

Rostam King

Simon James Fenney

Gregory Clark

Peter Smith-Lacey

William Thomas

Kenneth C Rovers

A method of operation of a texturing/shading unit in a GPU pipeline is used for efficient convolution operations. The method uses texture hardware to collectively fetch all the texels required to calculate properties for a group of output pixels without any duplication. The method then bypasses bilinear filter hardware in the texture hardware and passes the fetched and unfiltered texel data from the texture hardware unit to shader hardware in the texturing/shading unit. The shader hardware uses the fetched texel data to perform a plurality of convolution operations to calculate the properties of each of the output pixel.

Texturing/shading in a GPU pipeline bypassing bilinear filter

A method and an intersection testing module for performing intersection testing in a ray tracing system determines a first offset intersection distance which is equal to a sum of an intersection distance at which a ray intersects a first primitive and a first offset which is dependent upon the orientation of the first primitive. A second offset intersection distance is determined which is equal to a sum of an intersection distance at which the ray intersects a second primitive and a second offset which is dependent upon the orientation of the second primitive. The determined first and second offset intersection distances are compared to select the intersection of the ray with one of the first and second primitives.

Intersection testing in a ray tracing system using offset intersection distances

A method and intersection testing module are provided in a ray tracing system for determining whether a ray intersects a 3D axis-aligned box. The box represents a volume defined by a front-facing plane and a back-facing plane for each of the dimensions of the three-dimensional axis-aligned box. Scaled ray components are determined, wherein a third scaled ray component equals 1. A scaled minimum culling distance and a scaled maximum culling distance are determined. Determined cross-multiplication values are used to identify which of the front-facing planes intersects the ray furthest along the ray and identify which of the back-facing planes intersects the ray least far along the ray. It is determined whether the ray intersects the identified front-facing plane of the box at a position that is no further along the ray than the position at which the ray intersects the identified back-facing plane.

Intersection testing in a ray tracing system using scaled ray components

A method and an intersection testing module for performing intersection testing in a ray tracing system determines that a difference between an intersection distance at which a ray intersects a first primitive and an intersection distance at which the ray intersects a second primitive satisfies a comparison condition with respect to a threshold. It is determined that the orientations of the first and second primitives are different. The intersection of the ray with one of the first and second primitives is selected on the basis that the one of the first and second primitives has a particular orientation.

Intersection testing in a ray tracing system

A method of performing anisotropic texture filtering includes generating one or more parameters describing an elliptical footprint in texture space; performing isotropic filtering at each of a plurality of sampling points in an ellipse to be sampled, the ellipse to be sampled based on the elliptical footprint; and combining results of the isotropic filtering at each of the plurality of sampling points to generate a combination result by a sequence of linear interpolations, wherein each linear interpolation in the sequence of linear interpolations comprises blending a result of a previous linear interpolation in the sequence with the isotropic filtering results for one or more of the plurality of sampling points, the one or more of the plurality of sampling points for a linear interpolation being closer to a midpoint of the major axis of the elliptical footprint than the one or more of the plurality of sampling points for the previous linear interpolation in the sequence.

Anisotropic texture filtering by combining isotropic filtering results at each of a plurality of sampling points

A method and an intersection testing module for performing intersection testing in a ray tracing system determines if a difference between an intersection distance at which a ray intersects a first primitive and an intersection distance at which the ray intersects a second primitive satisfies a comparison condition with respect to a threshold, and if the orientations of the first and second primitives are different. If so the intersection of the ray with the one of the first and second primitives which has a particular orientation is selected.

Intersection testing in a ray tracing system using comparison of intersection distance differences between primitive intersections

Methods and hardware for texture address generation receive fragment coordinates for an input block of fragments and texture instructions for the fragments and calculating gradients for at least one pair of fragments. Based on the gradients, the method determines whether a first mode or a second mode of texture address generation is to be used and then uses the determined mode and the gradients to perform texture address generation. The first mode of texture address generation performs calculations at a first precision for a subset of the fragments and calculations for remaining fragments at a second, lower, precision. The second mode of texture address generation performs calculations for all fragments at the first precision and if the second mode is used and more than half of the fragments in the input block are valid, the texture address generation is performed over two clock cycles.

Texture address generation using fragment pair differences

A ray tracing system and method for processing data in which a forward transformation indication is received defining a transformation from a first space to a second space. A transformation is performed on input data from the second space to the first space to determine transformed data by performing a reverse translation operation on the input data, wherein the reverse translation operation is the reverse of a translation defined by the forward transformation indication. An inverse linear mapping operation is performed on the result of the reverse translation operation, wherein the inverse linear mapping operation is the inverse of a linear mapping defined by the forward transformation indication. The transformed data is processed in the ray tracing system.

Transformation of data in a ray tracing system

A method of performing anisotropic texture filtering includes generating one or more parameters describing an elliptical footprint in texture space; performing isotropic filtering at each sampling point of a set of sampling points in an ellipse to be sampled to produce a plurality of isotropic filter results, the ellipse to be sampled based on the elliptical footprint; selecting, based on one or more parameters of the set of sampling points and one or more parameters of the ellipse to be sampled, weights of an anisotropic filter that minimize a cost function that penalises high frequencies in the filter response of the anisotropic filter under a constraint that the variance of the anisotropic filter is related to an anisotropic ratio squared, the anisotropic ratio being the ratio of a major radius of the ellipse to be sampled and a minor axis of the ellipse to be sampled; and combining the plurality of isotropic filter results using the selected weights of the anisotropic filter to generate at least a portion of a filter result.

Anisotropic texture filtering using weights of an anisotropic filter that minimize a cost function

A method of performing anisotropic texture filtering includes generating one or more parameters describing an elliptical footprint in texture space; performing isotropic filtering at each of a plurality of sampling points along a major axis of the elliptical footprint, wherein a spacing between adjacent sampling points of the plurality of sampling points is proportional to √{square root over (1−η)} units, wherein η is a ratio of a major radius of an ellipse to be sampled and a minor radius of the ellipse to be sampled, wherein the ellipse to be sampled is based on the elliptical footprint; and combining results of the isotropic filtering at the plurality of sampling points with a Gaussian filter to generate at least a portion of a filter result.

Anisotropic texture filtering by combining results of isotropic filtering at a plurality of sampling points with a gaussian filter

Methods and hardware for cube mapping comprise receiving fragment coordinates for an input block of fragments and texture instructions for the fragments and then determining, based on gradients of the input block of fragments, whether a first mode of cube mapping or a second mode of cube mapping is to be used, wherein the first mode of cube mapping performs calculations at a first precision for a subset of the fragments and calculations for remaining fragments at a second, lower, precision and the second mode of cube mapping performs calculations for all fragments at the first precision. Cube mapping is then performed using the determined mode and the gradients, wherein if the second mode is used and more than half of the fragments in the input block are valid, the cube mapping is performed over two clock cycles.

Cube mapping using gradients of an input block of fragments

A method and an intersection testing module in a ray tracing system for determining whether a ray intersects a three-dimensional axis-aligned box. It is determined whether a first condition is satisfied, wherein the first condition is, or is equivalent to, It is determined whether a second condition is satisfied, wherein the second condition is, or is equivalent to, It is determined whether a third condition is satisfied, wherein the third condition is, or is equivalent to, The determinations of whether the first, second and third conditions are satisfied are used to determine whether the ray intersects the axis-aligned box. C, Cand Care x, y and z components of a position of the centre of the axis-aligned box relative to an origin of the ray, H, Hand Hare half widths of the axis-aligned box in the x, y and z dimensions, and D, Dand Dare x, y and z components of a direction vector of the ray.

Intersection testing in a ray tracing system using axis-aligned box coordinate components

An image processing method and an image processing unit for performing image processing determines a set of one or more filtered pixel values, wherein the one or more filtered pixel values represent a result of processing image data using a set of one or more filtering functions. A total covariance of the set of one or more filtering functions is identified. A refinement filtering function is applied to the set of one or more filtered pixel values to determine a set of one or more refined pixel values, wherein the refinement filtering function has a covariance that is determined based on the total covariance of the set of one or more filtering functions.

Image processing using filtering function covariance

A texture filtering unit applies anisotropic filtering using a filter kernel which can be adapted to apply different amounts of anisotropy up to a maximum amount of anisotropy. If it is determined that a received input amount of anisotropy is not above the maximum amount of anisotropy, the filter kernel applies the input amount of anisotropy, and texels of a texture are sampled using the filter kernel to determine a filtered texture value. If it is determined that the input amount of anisotropy is above the maximum amount of anisotropy, the filter kernel applies an amount of anisotropy that is not above the maximum amount of anisotropy, a plurality of sampling operations are performed to sample texels of the texture using the filter kernel to determine a respective plurality of intermediate filtered texture values, and the plurality of intermediate filtered texture values are combined to determine a filtered texture value which has been filtered in accordance with the input amount of anisotropy and the input direction of anisotropy.

Anisotropic texture filtering using adaptive filter kernel

Texture filtering in computer graphics calculates first and second pairs of texture-space basis vectors that correspond to first and second pairs of screen-space basis vectors transformed to texture space under a local approximation of a mapping between screen space and texture space. Based on differences in magnitudes of the vectors of the pairs of texture-space basis vectors, an angular displacement is determined between a selected pair of the first and second pairs of screen-space basis vectors and screen-space principal axes of the local approximation of the mapping that indicate maximum and minimum scale factors of the mapping. The determined angular displacement and the selected pair of screen-space basis vectors are used to generate texture-space principal axes, with a major axis associated with the maximum scale factor of the mapping and a minor axis associated with the minimum scale factor of the mapping. A texture is filtered using the major and minor axes.

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Rostam King