Imagination Technologies Limited

Lorenzo Belli

Robert Brigg

Xile Yang

Richard Broadhurst

John William Howson

Jonathan Mark Redshaw

Andrea Sansottera

A method of processing primitives within a tiling unit of a graphics processing system comprises determining whether a primitive falls within a tile based on positions of samples within each pixel. If it is determined that the primitive does fall within a tile based on the positions of samples within pixels in a tile, an association between the tile and the primitive is stored to indicate that the primitive is present in the tile. For example, an identifier for the primitive may be added to a control stream for the tile to indicate that the primitive is present in the tile. Various different methods are described to make the determination and these may be used separately or in any combination.

Generation of a control stream for a tile

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 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

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

Tiling engines and methods for hierarchically tiling a plurality of primitives. A chain of sorting units includes a top level sorting unit followed by lower level sorting units, the top level sorting unit determining which of a plurality of regions of a render space each of the plurality of primitives at least partially falls within. For each region a primitive at least partially falls within an identifier of that primitive is stored in a queue. Each of the lower level sorting units selects queues of a preceding sorting unit in the chain to process, and determines which of a plurality of sub-regions of the region associated with that queue each of the primitives at least partially falls within. For each such sub-region an identifier of that primitive is stored in a queue of the lower level sorting unit that is associated with that sub-region. An output unit outputs the primitives identified in the queues of the last lower level sorting unit in the chain on a queue by queue basis.

Hierarchical tiling in a graphics processing system using chain sorting of primitives

Virtual memory management

A method of processing primitives within a tiling unit of a graphics processing system is described. The method comprises determining whether a primitive falls within a tile based on positions of samples within each pixel. If it is determined that the primitive does fall within a tile based on the positions of samples within pixels in a tile, an association between the tile and the primitive is stored to indicate that the primitive is present in the tile. For example, an identifier for the primitive may be added to a control stream for the tile to indicate that the primitive is present in the tile. Various different methods are described to make the determination and these may be used separately or in any combination.

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 is obtained, which identifies a depth range based on primitives previously processed for the tile. 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 as to whether the primitive, or one or more primitive fragments thereof has better depth than the primitives previously processed for the tile according to a depth compare mode. 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.

Tiling engines and methods for use in a graphics processing system for hierarchically tiling a plurality of primitives. The tiling engine includes: a chain of sorting units comprising a top level sorting unit followed by one or more lower level sorting units, wherein: the top level sorting unit is configured to: determine which of a plurality of regions of a render space each of the plurality of primitives, at least partially, falls within; and for each region a primitive, at least partially, falls within, store an identifier of that primitive in a queue of the top level sorting unit that is associated with that region; and each of the one or more lower level sorting units is configured to: select one or more queues of a preceding sorting unit in the chain to process; for each of the selected queues, determine which of a plurality of sub-regions of the region associated with that queue each of the primitives identified in that queue, at least partially, falls within; and for each sub-region a primitive, at least partially, falls within, store an identifier of that primitive in a queue of the lower level sorting unit that is associated with that sub-region; and an output unit configured to output the primitives identified in the queues of the last lower level sorting unit in the chain on a queue by queue basis.

When untransformed display lists are used in a tile-based graphics processing system, the processing involved in deriving sub-primitives may need to be performed in both the geometry processing phase and the rasterization phase. To reduce the duplication of this processing, the control stream data for a tile includes sub-primitive indications to indicate which sub-primitives are to be used for rendering a tile. This allows the sub-primitives to be determined efficiently in the rasterization phase based on this information determined in the geometry processing phase. Furthermore, a hierarchical cache system may be used to store a hierarchy of graphics data items used for deriving sub-primitives. If graphics data items for deriving a sub-primitive are stored in the cache, the retrieval of these graphics data items from the cache in the rasterization phase can reduce the amount of processing performed to derive the sub-primitives.

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Watford, United Kingdom

Lorenzo Belli