Parallel Line Stipple Computation via Phase Broadcasting
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Solution Overview
Problem
Existing graphics processing systems struggle to compute line stipple phases in parallel, leading to serial rasterization of stippled lines, which limits performance when using parallel rasterization pipelines.
Innovation Solution
A system and method for computing line stipple phases in parallel by accumulating and broadcasting an update phase message across multiple parallel rasterizers, allowing each rasterizer to reconstruct the stipple phase for individual line segments while maintaining API primitive ordering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If parallel rasterization pipelines are used to render stippled lines, then rendering throughput is improved, but stipple phase computation becomes complex and requires serialization
Solution Approach 1:
The patent divides the stipple phase computation into per-segment independent calculations. Each rasterizer computes stipple phases for its assigned line segments independently using the formula: stipple_phase = (segment_start_parameter - line_start_parameter) * stipple_frequency + line_start_stipple_phase. This segmentation eliminates the need for serialization while maintaining correct stipple phase continuity across segments.
Solution Approach 2:
The patent performs preliminary computation of line_start_stipple_phase for each line segment before parallel rasterization. This pre-computed initial phase value is passed to each rasterizer, allowing them to independently calculate subsequent segment phases without requiring inter-rasterizer communication or serialization.
2Device complexity
If a single rasterization pipeline is used to process all line segments, then stipple phase tracking is simple, but rendering performance is limited
Solution Approach 1:
The patent enables each rasterizer to have its own independent stipple phase computation tailored to its specific line segments. Each rasterizer uses the local line_start_stipple_parameter and line_start_stipple_phase values specific to its assigned segments, allowing parallel processing while maintaining correct local stipple phase continuity.
3Productivity
If multiple parallel rasterizers are used, then rendering speed is improved, but maintaining API primitive ordering becomes challenging
Solution Approach 1:
The system performs preliminary sorting of line segments by their line_start_parameter value before distribution to parallel rasterizers. This pre-ordering ensures that when multiple rasterizers process segments in parallel, they all operate on segments in the correct API primitive order, maintaining stability without requiring post-processing synchronization.
Solution Approach 2:
The patent segments the line strip into independent line segment primitives that can be independently processed by different rasterizers. Each segment carries its own line_start_stipple_parameter and line_start_stipple_phase, allowing parallel processing while maintaining the original API primitive ordering through the preliminary sort.
Data Source
AI summary
One embodiment of the present invention sets forth a technique for computing line stipple using a parallel rasterizer. Stipple phases are computed in parallel for individual line segments of a line strip during the viewport scale, cull, and clipping operations. The line segments are distributed to multiple parallel rasterizers. Each line segment may be sent to only one of the parallel rasterizers. Update phase messages that include an accumulated stipple phase for a batch of line segments are broadcast to all of the multiple parallel rasterizers. The update phase messages are used by the multiple parallel rasterizers to reconstruct the stipple phases for each line segment of a line strip in order to correctly render stippled line strips and produce a continuous stippled line.