Abstract: A computer-implemented method of performing intersection testing in a ray tracing system performs intersection testing for each of a plurality of rays against nodes of a hierarchical acceleration structure. The intersection testing for each of the rays comprises, in response to identifying, in a memory, an indication of a re-entry point associated with a ray identifier that is associated with the ray, fetching from the memory the indication of the re-entry point that is associated with the ray identifier, the re-entry point being a node of the hierarchical acceleration structure for which an intersection has been identified for a previously tested ray associated with the ray identifier. The intersection testing for each of the rays further comprises performing intersection testing of the ray against a set of nodes of the hierarchical acceleration structure starting from the re-entry point.

Abstract: A computer implemented method converts ray data for a ray into a ray representative, wherein the ray representative is a compressed representation of the ray data, and wherein the ray data comprises three direction components and three position components for the ray. The method comprises identifying which of the three direction components of the ray data has the greatest magnitude, and defining the axis of the identified direction component as the major axis of the ray. The method further comprises determining a translated position on the ray at which the position component along the major axis is zero, and rescaling the three direction components of the ray so that the magnitude of the direction component along the major axis is one. The ray representative comprises: (i) the two position components of the translated position along the axes which are not the major axis, and (ii) the two rescaled direction components along the axes which are not the major axis.

Abstract: 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.

Abstract: A computer-implemented method for decompressing compressed data, the compressed data representing an n-bit decompressed data value, the compressed data comprising a first compressed subset of bits and a second compressed subset of bits, the first compressed subset representing the n?2 most significant bits of the decompressed data value and the second compressed subset representing the two least significant bits of the decompressed data value, the method comprising performing decompression of the first compressed subset using a first decompression module to determine the n?2 most significant bits of the decompressed data value; performing decompression of the second compressed subset using a second decompression module to determine the two least significant bits of the decompressed data value, the first and second decompression modules implementing different decompression schemes; and combining the determined n?2 most significant bits of the decompressed data value and the determined two least significant bit

Abstract: A computer-implemented method of performing intersection testing in a ray tracing system performs intersection testing for each of a plurality of rays against nodes of a hierarchical acceleration structure. The intersection testing for each of the rays comprises, in response to identifying, in a memory, an indication of a re-entry point associated with a ray identifier that is associated with the ray, fetching from the memory the indication of the re-entry point that is associated with the ray identifier, the re-entry point being a node of the hierarchical acceleration structure for which an intersection has been identified for a previously tested ray associated with the ray identifier. The intersection testing for each of the rays further comprises performing intersection testing of the ray against a set of nodes of the hierarchical acceleration structure starting from the re-entry point.

Abstract: A computer-implemented method for compressing, an input group of m data values compresses the two least significant bits of each of the data values by mapping the two least significant bits of each of the data values in the input group of m data values collectively onto an m-bit encoding and storing the m-bit encoding, the m-bit encoding being selected from 2m m-bit encodings, the 2m m-bit encodings comprising a first group of encodings comprising (2m?4) m-bit encodings and a second group of encodings comprising four m-bit encodings, wherein if the selected encoding is an encoding from the first group of encodings then the selected encoding represents the two least significant bits for a representative group of m data values in which the second least significant bit of each of the data values is the same as a respective bit of the m-bit encoding, and wherein if the selected encoding is an encoding from the second group of encodings then the selected encoding represents the two least significant bits for a rep

Abstract: 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.

Abstract: 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.

Abstract: Intersection testing in a ray tracing system is performed for a ray with respect to a primitive. An intersection attribute value is determined for a primary sample of the ray relating to an intersection between the ray and the primitive in a ray coordinate system. The ray coordinate system has two non-parallel axes that are both transverse to the direction of the ray, and an origin of the ray coordinate system is on the ray. For one or both of the two non-parallel axes of the ray coordinate system, data is determined indicating a change to the intersection attributes in a direction parallel to that axis. The intersection between the ray and the primitive is processed using the determined value of the intersection attributes for the primary sample of the ray and the determined data indicating a change to the intersection attributes in the directions parallel to the two non-parallel axes.

Abstract: 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.

Abstract: 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.

Abstract: A computer-implemented method for compressing, an input group of m data values compresses the two least significant bits of each of the data values by mapping the two least significant bits of each of the data values in the input group of m data values collectively onto an m-bit encoding and storing the m-bit encoding, the m-bit encoding being selected from 2m m-bit encodings, the 2m m-bit encodings comprising a first group of encodings comprising (2m?4) m-bit encodings and a second group of encodings comprising four m-bit encodings, wherein if the selected encoding is an encoding from the first group of encodings then the selected encoding represents the two least significant bits for a representative group of m data values in which the second least significant bit of each of the data values is the same as a respective bit of the m-bit encoding, and wherein if the selected encoding is an encoding from the second group of encodings then the selected encoding represents the two least significant bits for a rep

Abstract: A ray tracing system determines whether a ray intersects a three-dimensional axis-aligned box by determining whether a minimum distance condition and a maximum distance condition are satisfied, wherein the determining comprises determining whether a single distance condition is satisfied. The determination is used to determine whether the ray intersects the axis-aligned box. A point on the ray is at a position O+Dt where O is a vector which represents an origin of the ray, and t represents a distance along the ray from the origin of the ray, and wherein D is a 3D vector defining a direction vector of the ray.

Abstract: A method of performing intersection testing in a ray tracing system, for a ray with respect to a set of two or more primitives. Each primitive is defined by an ordered set of edges, and each edge is defined by a respective pair of vertices. A set of distinct edges is determined for the set of primitives, each distinct edge being part of at least one primitive of the set of primitives and being defined by a different pair of vertices to the other distinct edges in the set, wherein every edge in the ordered sets of edges that define the set of primitives is represented by a distinct edge of the set of distinct edges. For each distinct edge in the set of distinct edges, an edge test is performed to determine which side of the distinct edge the ray passes on. For each primitive in the set of primitives, a result of the edge test is used for each distinct edge that defines that primitive to determine whether or not the ray intersects that primitive.

Abstract: A method of processing a primitive as part of intersection testing in a ray tracing system, the primitive being defined by an ordered set of vertices. Data defining a direction and an origin of a ray to be tested against the primitive, and coordinate data for a set of vertices are received. The coordinate data for the set of vertices is projected into ray space using the ray data, wherein the ray space has two non-parallel axes that are transverse to the direction of the ray, wherein a ray-space frame of reference associated with the axes is centered at a point on the ray such that the ray is represented as that point on the axes in the ray space, and wherein the point is an origin of the ray space. Then, the signs of the coordinate data for the set of vertices are analysed to determine whether a non-intersection condition is fulfilled, wherein fulfilment of the non-intersection condition indicates that the ray does not intersect the primitive.

Abstract: A method and an intersection testing module in a ray tracing system for performing intersection testing for a ray with respect to a plurality of convex polygons, each of which is defined by an ordered set of vertices. The vertices of the convex polygons are projected onto a pair of axes orthogonal to the ray direction. For each edge of a convex polygon defined by two of the projected vertices, a signed parameter is determined, wherein the sign of the signed parameter is indicative of which side of the edge the ray passes on. If the ray is determined to intersect a point on the edge then the sign of the signed parameter is determined using a module which is configured to: take as inputs, indications which classify each of pi, qi, pj and qj coordinates as negative, zero or positive, and output, for valid combinations of classifications of the pi, qi, pj and qj coordinates, an indication of the sign of the signed parameter.

Abstract: 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, ? "\[LeftBracketingBar]" C x - C z ? D x D z ? "\[RightBracketingBar]" ? H z ? D x D z + H x . It is determined whether a second condition is satisfied, wherein the second condition is, or is equivalent to, ? "\[LeftBracketingBar]" C y - C z ? D y D z ? "\[RightBracketingBar]" ? H z ? D y D z + H y .

Abstract: Methods and decoding units for decoding a compressed data structure to determine a decoded value. The compressed data structure encodes a set of Haar coefficients for a block of pixels, including a plurality of differential coefficients and a sum coefficient. The compressed data structure includes a set of exponent bits representing exponents of the differential coefficients, a set of sign bits representing signs for the differential coefficients, a set of sum bits representing the sum coefficient. The compressed data structure is unpacked to identify the set of exponent bits, the set of sign bits and the set of sum bits. The identified set of exponent bits is used to determine exponents for the differential coefficients. The identified set of sign bits is used to determine signs the differential coefficients. The identified set of sum bits is used to determine the sum coefficient.

Abstract: A method and an intersection testing module in a ray tracing system for performing intersection testing for a ray with respect to a plurality of convex polygons, each of which is defined by an ordered set of vertices. The vertices of the convex polygons are projected onto a pair of axes orthogonal to the ray direction. For each edge of a convex polygon defined by two of the projected vertices, a signed parameter is determined, wherein the sign of the signed parameter is indicative of which side of the edge the ray passes on. If the ray is determined to intersect a point on the edge then the sign of the signed parameter is determined using a module which is configured to: take as inputs, indications which classify each of pi, qi, pj and qj coordinates as negative, zero or positive, and output, for valid combinations of classifications of the pi, qi, pj and qj coordinates, an indication of the sign of the signed parameter.

Abstract: Methods and encoding units for encoding a block of pixels into a compressed data structure. A set of Haar coefficients is determined for the block of pixels, including differential coefficients and a sum coefficient. A set of exponent bits is determined representing exponents for the differential coefficients. A set of sign bits is determined representing signs for the differential coefficients. A set of sum bits is determined representing the sum coefficient. The determined set of exponent bits is packed into a first portion of the compressed data structure; the determined set of sign bits is packed into a second portion of the compressed data structure; and the determined set of sum bits is packed into a third portion of the compressed data structure. The compressed data structure is stored.