Variable Rasterization Tile Processing for Large Primitives
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Solution Overview
Problem
Conventional graphics processors face performance bottlenecks in rasterization, particularly when rendering large graphics primitives with trivial shaders, due to limited memory bandwidth and excessive per-pixel sample computations, leading to underutilization of memory bandwidth.
Innovation Solution
The method involves determining whether pixel tiles are fully or partially covered by a graphics primitive and only computing coverage information for partially covered areas, eliminating unnecessary computations for fully covered tiles, and using sub-pixel samples for efficient compression and shading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If per-pixel sample computations are performed for all pixel tiles, then coverage information accuracy is maintained, but computational resources and rendering time increase
Solution Approach 1:
The patent applies partial action by computing coverage information only for pixel tiles that are partially covered by graphics primitives, rather than performing full per-pixel sample computations on all tiles. The system determines which tiles require coverage computation based on primitive-tile intersection analysis, and selectively processes only those tiles, thereby reducing unnecessary computational overhead while maintaining accuracy where needed.
Solution Approach 2:
The patent implements local quality by applying different processing strategies to different regions of the rendering scene. Fully covered tiles use simplified coverage determination, partially covered tiles undergo edge testing with per-sample coverage computation, and non-intersecting tiles are skipped entirely. This localized approach optimizes computational resources based on the specific coverage requirements of each tile region.
2Reliability
If rasterization computes per-pixel samples for all tiles, then rendering completeness is ensured, but memory bandwidth utilization decreases
Solution Approach 1:
The patent extracts and eliminates unnecessary per-pixel sample computations from the rasterization pipeline. By identifying pixel tiles that are fully covered or not intersecting with graphics primitives, the system removes redundant coverage computations and memory access operations, thereby increasing memory bandwidth availability for other rendering tasks while maintaining rendering completeness through selective processing.
Solution Approach 2:
The system performs partial rasterization by processing only the necessary subset of pixel tiles rather than all tiles in the scene. This selective approach ensures rendering completeness for visible geometry while avoiding excessive memory bandwidth consumption associated with processing fully covered or non-intersecting tiles, thus optimizing memory utilization.
3Reliability
If full rasterization is performed on all pixel tiles, then no rendering artifacts are produced, but computational complexity increases
Solution Approach 1:
The patent segments the pixel tile processing into distinct categories: fully covered tiles, partially covered tiles, and non-intersecting tiles. Each segment receives appropriate processing - fully covered tiles use simplified coverage determination, partially covered tiles undergo edge testing with per-sample coverage computation, and non-intersecting tiles are skipped. This segmentation reduces computational complexity while maintaining rendering quality through targeted processing of each segment type.
Solution Approach 2:
The system applies local quality by using different computational approaches for different tile regions based on their coverage characteristics. Edge testing and per-sample coverage computation are applied locally only to partially covered tiles where needed, while fully covered tiles use simpler coverage determination. This localized differentiation reduces overall computational complexity while preserving rendering quality.
Data Source
AI summary
The current invention involves new systems and methods for providing variable rasterization performance suited to the size and shape of the primitives being rendered. Portions of pixel tiles that are fully covered by a graphics primitive are encoded and processed by the system as rectangles, rather than expanding to explicit samples. This accelerates the rendering of large primitives without increasing the computation resources used for rasterization. In some embodiments, these fully-covered regions can be rendered compressed without ever expanding into samples.