Imagination Technologies Limited

Robert Brigg

Xile Yang

John William Howson

Lorenzo Belli

Panagiotis Velentzas

Diego Jesus

Michael John Livesley

A method of managing access to a physical memory formed of n memory page frames using a set of virtual address spaces having n virtual address spaces each formed of a plurality p of contiguous memory pages. The method includes receiving a write request to write a block of data to a virtual address within a virtual address space i of the n virtual address spaces, the virtual address defined by the virtual address space i, a memory page j within that virtual address space i and an offset from the start of that memory page j; translating the virtual address to an address of the physical memory using a virtual memory table having n by p entries specifying mappings between memory pages of the virtual address spaces and memory page frames of the physical memory, wherein the physical memory address is defined by: (i) the memory page frame mapped to the memory page j as specified by the virtual memory table, and (ii) the offset of the virtual address; and writing the block of data to the physical memory address.

Managing access to memory by determining virtual addresses in dependence on access request type

Methods and tiling engines for tiling primitives in a tile based graphics processing system in which a rendering space is divided into a plurality of tiles. The method includes generating a multi-level hierarchy of tile groups, each level of the multi-level hierarchy comprising one or more tile groups comprising one or more of the plurality of tiles; receiving a plurality of primitive blocks, each primitive block comprising geometry data for one or more primitives; associating each of the plurality of primitive blocks with one or more of the tile groups up to a maximum number of tile groups such that if at least one primitive of a primitive block falls, at least partially, within the bounds of a tile, the primitive block is associated with at least one tile group that includes that tile; and generating a control stream for each tile group based on the associations, wherein each control stream comprises a primitive block entry for each primitive block associated with the corresponding tile group.

Data structures, methods and tiling engines for hierarchically storing tiling information in a graphics processing system

Methods and graphics processing systems render items of geometry using a rendering space which is subdivided into a plurality of first regions. Each of the first regions is sub-divided into a plurality of second regions. Each of a plurality of items of geometry is processed by identifying which of the first regions the item of geometry is present within, and for each identified first region determining an indication of the spatial coverage, within the identified first region, of the item of geometry, and using the determined indication of the spatial coverage within the identified first region to determine whether to add the item of geometry to a first control list for the identified first region or to add the item of geometry to one or more second control lists for a respective one or more of the second regions within the identified first region. Items of geometry within a second region can then be rendered using: (i) the first control list for the first region of which the second region is a part, and (ii) the second control list for the second region.

Graphics processing method and system for rendering items of geometry based on their size

Data structures, methods and tiling engines for storing tiling data in memory wherein the tiles are grouped into tile groups and the primitives are grouped into primitive blocks. The methods include, for each tile group: determining, for each tile in the tile group, which primitives of each primitive block intersect that tile; storing in memory a variable length control data block for each primitive block that comprises at least one primitive that intersects at least one tile of the tile group; and storing in memory a control stream comprising a fixed sized primitive block entry for each primitive block that comprises at least one primitive that intersects at least one tile of the tile group, each primitive block entry identifying a location in memory of the control data block for the corresponding primitive block. Each primitive block entry may comprise valid tile information identifying which tiles of the tile group are valid for the corresponding primitive block. A tile is a valid tile for a primitive block if at least one primitive in the primitive block intersects that tile.

Data structures, methods and tiling engines for storing tiling information in a graphics processing system

Methods and primitive block generators for generating primitive blocks in a graphics processing system. The methods include receiving transformed position data for a current primitive, the transformed position data indicating a position of the current primitive in rendering space; determining a distance between the position of the current primitive and a position of a current primitive block based on the transformed position data for the current primitive; determining whether to add the current primitive to the current primitive block based on the distance and a fullness of the current primitive block; in response to determining that the current primitive is to be added to the current primitive block, adding the current primitive to the current primitive block; and in response to determining that the current primitive is not to be added to the current primitive block, flushing the current primitive block and adding the current primitive to a new current primitive block.

Primitive block generator for graphics processing systems

A graphics processing system for generating a rendering output includes geometry processing logic having first transformation logic configured to transform a plurality of untransformed primitives into a plurality of transformed primitives, the first transformation logic configured to implement one or more expansion transformation stages which generate one or more sub-primitives; a primitive block generator configured to divide the plurality of transformed primitives into a plurality of groups; and generate an untransformed primitive block for each group comprising (i) information identifying the untransformed primitives related to the transformed primitives in the group; and (ii) an expansion transformation stage mask for at least one or more expansion transformation stages that indicates the sub-primitives generated for the untransformed primitives in that untransformed primitive block used in generating the rendering output. Rasterization logic includes second transformation logic configured to re-transform the plurality of untransformed primitives into the plurality of transformed primitives on an untransformed primitive block-basis in accordance with the expansion transformation stage mask for the one or more expansion transformation stages; and logic configured to render the transformed primitives to generate the rendering output.

Graphics processing systems with expansion transformation stage masks

Graphics processing renders primitives using a rendering space which is subdivided into a plurality of regions. A geometry processing phase determines, for each of a plurality of primitives which are present in a region, whether the primitive totally covers the region and stores data for the primitives which are determined to totally cover the region to indicate total coverage of the region. A rendering phase retrieves the stored data for the primitives which are present in the region, selectively processes primitives which are present in the region based on the retrieved data to determine which sample points within the region are covered by the primitives, wherein if the retrieved data includes data which indicates total coverage of the region for a particular primitive then the processing determining sample points is skipped; and determines rendered values at the sample points within the region based on the primitives which cover the respective sample points.

A set of two or more variable length data blocks is stored in memory. Each variable length data block has a maximum size of N*B, wherein N is an integer greater than or equal to two, and B is a maximum data size that can be written to the memory using a single memory access request. For each variable length data block of the set, the first P non-overlapping portions of size B of the variable length data block are stored in a chunk of the memory allocated to that variable length data block, wherein P is a minimum of (i) a number of non-overlapping portions of size B of the variable length data block and (ii) X which is an integer less than N. Any remaining portions of the variable length data blocks are stored in a remainder section of the memory shared between the variable length data blocks of the set. Information indicating the size of each of the variable length data blocks in the set is stored in a header.

Methods and systems for storing variable length data blocks in memory

Methods and control stream generators for generating a control stream for a tile group comprising at least two tiles, the control stream identifying primitive blocks that are relevant to rendering at least one tile in the tile group. Information is received identifying one or more primitive blocks relevant to rendering at least one tile in the tile group, each primitive block comprising one or more primitives; generating a primitive block entry for each of the identified primitive blocks; and adding each primitive block entry to the control stream; wherein generating the primitive block entry for at least one of the identified primitive blocks comprises: (i) identifying a bounding box encompassing the one or more primitives of the primitive block; (ii) generating a coverage mask that indicates which tiles of the tile group that intersect the bounding box for the primitive block are valid for the primitive block, a tile being valid for a primitive block if at least one primitive of the primitive blocks falls, at least partially, within the bounds of the tile; and (iii) including the coverage mask in the primitive block entry.

Methods and control stream generators for generating a control stream for a tile group in a graphics processing system

Methods and coarse depth test logic perform coarse depth testing in a graphics processing system in which a rendering space is divided into a plurality of tiles. A depth range for a tile identifies a depth range based on primitives previously processed. A determination is made based on the depth range for the tile as to whether all or a portion of a primitive is hidden in the tile. If at least a portion of the primitive is not hidden in the tile, a determination is made as to whether the primitive or a primitive fragment thereof has better depth than the primitives previously processed for the tile. If so, the primitive or the primitive fragment is identified as not requiring a read of a depth buffer to perform full resolution depth testing, such that a determination that at least a portion of the primitive is hidden in the tile causes full resolution depth testing not to be performed on at least that portion of the primitive.

Coarse depth test in graphics processing systems

A tag buffer implements a tag buffer stage of a rasterization phase in a tile-based rendering graphics processing system having a rendering space sub-divided into a plurality of tiles to which primitives can be associated. A buffer stores an identifier that identifies a visible primitive fragment at each sample position of a tile of the plurality of tiles. A look-up table stores an entry for transformed primitive blocks that indicates whether the tag buffer has received information identifying a primitive fragment associated with that transformed primitive block. The tag buffer receives information identifying primitive fragments that have survived a depth test, updates the buffer to indicate that an identified primitive fragment is the visible primitive fragment at the associated sample position, updates the look-up table to indicate which transformed primitive blocks the identified primitive fragments are associated with, and in response to flushing the contents of the buffer, compares the flushed contents of the buffer to the look-up table to thereby identify transformed primitive blocks that did not survive the tag buffer stage.

Transformed geometry data cache for graphics processing systems

Systems and methods for processing primitive fragments in a rasterization phase of a graphics processing system wherein a rendering space is subdivided into a plurality of tiles. The method includes receiving a plurality of primitive fragments, each primitive fragment corresponding to a pixel sample in a tile; determining whether a depth buffer read is to be performed for hidden surface removal processing of one or more of the primitive fragments; sorting the primitive fragments into a priority queue and a non-priority queue based on the depth buffer read determinations; and performing hidden surface removal processing on the primitive fragments in the priority and non-priority queues wherein priority is given to the primitive fragments in the priority queue.

Primitive fragment processing in the rasterization phase of a graphics processing system

Methods and primitive block generators for generating primitive blocks in a graphics processing system. The methods comprise: receiving transformed position data for a current primitive, the transformed position data indicating a position of the current primitive in rendering space; determining a distance between the position of the current primitive and a position of a current primitive block based on the transformed position data for the current primitive; determining whether to add the current primitive to the current primitive block based on the distance and a fullness of the current primitive block; in response to determining that the current primitive is to be added to the current primitive block, adding the current primitive to the current primitive block; and in response to determining that the current primitive is not to be added to the current primitive block, flushing the current primitive block and adding the current primitive to a new current primitive block.

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Watford, United Kingdom

Robert Brigg