Abstract: Methods and graphics processing units for processing a plurality of fragments in a graphics processing system. A received first fragment is processed by performing an early depth test with hidden surface removal logic using a depth buffer; in response to the first fragment passing the early depth test, executing one or more instructions of a shader program for the first fragment on the processing logic to determine the property of the first fragment; and after the determination of the property of the first fragment, performing a late depth test on the first fragment with the hidden surface removal logic using the depth buffer. After said receiving a first fragment, a second fragment to be processed is received, wherein the second fragment does not have a shader-dependent property. The second fragment is processed by, before said late depth test is performed on the first fragment, performing an early depth test on the second fragment with the hidden surface removal logic.

Abstract: 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.

Abstract: A graphics processing system configured to use a rendering space which is subdivided into a plurality of tiles, includes geometry processing logic having geometry transform and sub-primitive logic configured to receive graphics data of input graphics data items, and to determine transformed positions within the rendering space of one or more sub-primitives derived from the input graphics data items using a plurality of shader stages; and a tiling unit configured to generate control stream data including sub-primitive indications to indicate which of the sub-primitives are to be used for rendering each tile. The geometry processing logic is configured to write to a memory, for each instance of a pre-determined shader stage, shader stage output data comprising data output from each instance of the pre-determined shader stage used to process the received graphics data.

Abstract: A method and system for generating and shading a computer graphics image in a tile based computer graphics system is provided. Geometry data is supplied and a plurality of primitives are derived from the geometry data. One or more modified primitives are then derived from at least one of the plurality of primitives. For each of a plurality of tiles, an object list is derived including data identifying the primitive from which each modified primitive located at least partially within that tile is derived. Alternatively, the object list may include data identifying each modified primitive located at least partially within that tile. Each tile is then shaded for display using its respective object list.

Abstract: 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.

Abstract: 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.

Abstract: Ray tracing units, processing modules and methods are described for generating one or more reduced acceleration structures to be used for intersection testing in a ray tracing system for processing a 3D scene. Nodes of the reduced acceleration structure(s) are determined, wherein a reduced acceleration structure represents a subset of the 3D scene. The reduced acceleration structure(s) are stored for use in intersection testing. Since the reduced acceleration structures represent a subset of the scene (rather than the whole scene) the memory usage for storing the acceleration structure is reduced, and the latency in the traversal of the acceleration structure is reduced.

Abstract: A graphics processing engine has a geometry shading stage having two modes of operation. In the first mode of operation, each primitive output by the geometry shading stage is independent, whereas in the second mode of operation, connectivity between input primitives is maintained by the geometry shading stage. The mode of operation of the geometry shading stage can be determined based on the value of control state data which may be generated at compile-time for a geometry shader based on analysis of that geometry shader.

Abstract: A ray tracing unit implemented in a graphics rendering system includes processing logic configured to perform ray tracing operations on rays, a dedicated ray memory coupled to the processing logic and configured to store ray data for rays to be processed by the processing logic, an interface to a memory system, and control logic configured to manage allocation of ray data to either the dedicated ray memory or the memory system. Core ray data for rays to be processed by the processing logic is stored in the dedicated ray memory, and at least some non-core ray data for the rays is stored in the memory system. This allows core ray data for many rays to be stored in the dedicated ray memory without the size of the dedicated ray memory becoming too wasteful when the ray tracing unit is not in use.

Abstract: A method and system for performing a render using a graphics processing unit that implements a tile-based graphics pipeline where a rendering space is sub-divided into tiles. Geometry data for the render is received, the geometry data including primitives associated with one or more vertex shader programs. The geometry data is processed using the vertex shader programs to generate processed primitives, and it is determined in which tile each of the processed primitives are located. For at least one selected tile there is stored i) a representation of per-tile vertex shader data identifying the one or more vertex shader programs used to generate the processed primitives in that tile, and ii) a representation of per-tile render data that can be used when rendering the processed primitives in that tile in subsequent stages of the graphics pipeline.

Abstract: A method and system for performing a render using a graphics processing unit that implements a tile-based graphics pipeline where a rendering space is sub-divided into tiles. Primitives are received that were processed by a geometry processing stage of the graphics pipeline and these are grouped into one or more sets, and a primitive block generated from each set. Primitive block data is stored characterising the content of the one or more primitive blocks. It is determined which tile each of the primitives are located in, and for at least one selected tile a per-tile primitive block list is stored indicating which of the one or more primitive blocks contain primitives located in that tile. It is determined whether the output of a previous render for the selected tile(s) can be used as an output for the render based on the per-tile primitive block list and the primitive block data for the primitive blocks indicated therein, and corresponding data from the previous render.

Abstract: 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.

Abstract: Methods and apparatus for merging tasks in a graphics pipeline in which, subsequent to a trigger to flush a tag buffer, one or more tasks from the flushed tag buffer are generated, each task comprising a reference to a program and plurality of fragments on which the program is to be executed, wherein a fragment is an element of a primitive at a sample position. It is then determined whether merging criteria are satisfied and if satisfied, one or more fragments from a next tag buffer flush are added to a last task of the one or more tasks generated from the flushed tag buffer.

Abstract: A graphics processing system configured to use a rendering space which is subdivided into a plurality of tiles, includes geometry processing logic having geometry transform and sub-primitive logic configured to receive graphics data of input graphics data items, and to determine transformed positions within the rendering space of one or more sub-primitives derived from the input graphics data items using a plurality of shader stages; and a tiling unit configured to generate control stream data including sub-primitive indications to indicate which of the sub-primitives are to be used for rendering each tile. The geometry processing logic is configured to write to a memory, for each instance of a pre-determined shader stage, shader stage output data comprising data output from each instance of the pre-determined shader stage used to process the received graphics data.

Abstract: A graphics processing unit (GPU) processes graphics data using a rendering space which is sub-divided into a plurality of tiles. The GPU comprises cost indication logic configured to obtain a cost indication for each of a plurality of sets of one or more tiles of the rendering space. The cost indication for a set of tile(s) is suggestive of a cost of processing the set of one or more tiles. The GPU controls a rendering complexity with which primitives are rendered in tiles based on the cost indication for those tiles. This allows tiles to be rendered in a manner that is suitable based on the complexity of the graphics data within the tiles. In turn, this allows the rendering to satisfy constraints such as timing constraints even when the complexity of different tiles may vary significantly within an image.

Abstract: A method and system is provided for culling hidden objects in a tile-based graphics system before they are indicated in a display list for a tile. A rendering space is divided into a plurality of regions which may for example be a plurality of tiles or a plurality of areas into which one or more tiles are divided. Depth thresholds for the regions, which are used to identify hidden objects for culling, are updated when an object entirely covers a region and in dependence on a comparison between a depth value for the object and the depth for the region. For example, if the depth threshold is a maximum depth threshold, the depth threshold may be updated if an object entirely covers the tile and the maximum depth value of the object is less than the maximum depth threshold.

Abstract: A graphics processing engine has a geometry shading stage having two modes of operation. In the first mode of operation, each primitive output by the geometry shading stage is independent, whereas in the second mode of operation, connectivity between input primitives is maintained by the geometry shading stage. The mode of operation of the geometry shading stage can be determined based on the value of control state data which may be generated at compile-time for a geometry shader based on analysis of that geometry shader.

Abstract: Methods and tessellation modules for tessellating a patch to generate tessellated geometry data representing the tessellated patch. Received geometry data representing a patch is processed to identify tessellation factors of the patch. Based on the identified tessellation factors of the patch, tessellation instances to be used in tessellating the patch are determined. The tessellation instances are allocated amongst a plurality of tessellation pipelines that operate in parallel, wherein a respective set of one or more of the tessellation instances is allocated to each of the tessellation pipelines, and wherein each of the tessellation pipelines generates tessellated geometry data associated with the respective allocated set of one or more of the tessellation instances.

Abstract: Methods of rendering a scene in a graphics system identify a draw call within a current render and analyse the last shader in the series of shaders used by the draw call to identify any buffers that are sampled by the last shader and that are to be written by a previous render that has not yet been sent for execution on the GPU. If any such buffers are identified, further analysis is performed to determine whether the last shader samples from the identified buffers using screen space coordinates that correspond to a current fragment location and if this determination is positive, the draw call is added to data relating to the previous render and the last shader is recompiled to replace an instruction that reads data from an identified buffer with an instruction that reads data from an on-chip register.

Abstract: 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.