Hierarchical Sub-Primitive Presence Encoding for Ray Tracing Latency
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Solution Overview
Problem
Existing ray tracing systems experience significant latency and power consumption due to the frequent execution of shader programs to determine the presence of punch through primitives during intersection testing, which is exacerbated by the use of sub-primitives for complex geometries with alpha-tested transparent textures.
Innovation Solution
A method of compressing sub-primitive presence indications using a hierarchical encoding approach, where presence states are represented in a block of compressed data, reducing the need for shader program execution by storing parent-level data for uniform regions and child-level data only for non-uniform regions, thereby optimizing data storage and processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sub-primitives are used for complex geometries with alpha-tested transparent textures, then geometric representation accuracy is improved, but the number of shader program executions increases significantly
Solution Approach 1:
The patent segments the primitive into multiple sub-primitives (e.g., sub-triangles) and evaluates transparency at representative sample points within each sub-primitive. This segmentation allows the system to avoid executing shader programs for every ray-sub-primitive intersection by instead using pre-evaluated presence indications stored in a data structure, thereby reducing shader execution frequency while maintaining geometric accuracy.
Solution Approach 2:
The patent performs preliminary evaluation of transparency by executing shader programs once during scene setup to determine presence indications for each sub-primitive at sample points. These results are stored in advance in a data structure that can be queried during ray tracing without re-executing shaders, thus performing the expensive shader operation beforehand to avoid repeated executions during rendering.
2Reliability
If frequent shader program executions are performed to determine primitive presence, then intersection testing accuracy is improved, but latency increases
Solution Approach 1:
The patent performs preliminary evaluation of primitive presence by executing shader programs during scene setup to determine transparency at sample points. These presence indications are stored in advance in a data structure, allowing the ray tracing system to query pre-computed results during intersection testing instead of executing shaders in real-time, thereby reducing latency while maintaining accuracy.
Solution Approach 2:
The patent creates a copied representation of presence information in a specialized data structure that mirrors the hierarchical organization of sub-primitives. This copied data structure stores pre-evaluated presence indications that can be efficiently queried during ray tracing, replacing the need to access original geometric data and re-evaluate shader conditions, thus reducing access time and latency.
3Measurement precision
If shader programs are executed frequently to check transparency, then rendering accuracy is improved, but power consumption increases
Solution Approach 1:
The patent performs shader program executions during scene setup rather than during active ray tracing. By pre-evaluating transparency and storing presence indications in a data structure, the system avoids repeated shader executions during rendering, significantly reducing power consumption while maintaining rendering accuracy through the pre-computed presence information.
Solution Approach 2:
The patent creates a copied presence information data structure that stores pre-evaluated transparency results. This copy allows the system to query rendering accuracy information without re-executing power-intensive shader programs, thereby maintaining rendering accuracy while dramatically reducing power consumption during the actual rendering process.
4Productivity
If presence indications are stored for all sub-primitives, then intersection testing efficiency is improved, but data storage requirements increase
Solution Approach 1:
The patent segments the data storage requirement by organizing presence indications in a hierarchical data structure that mirrors the sub-primitive hierarchy. This segmentation allows efficient querying during intersection testing while storing data in a compact organized form, balancing accessibility with storage efficiency.
Solution Approach 2:
The patent applies local quality by storing presence indications selectively based on the hierarchical organization of sub-primitives. The data structure allows different levels of detail to be stored and accessed locally, enabling efficient intersection testing for regions that require it while potentially reducing storage for regions where presence is uniformly determined, thus optimizing the balance between testing efficiency and storage requirements.
Data Source
AI summary
A block of sub-primitive presence indications for use in a rendering system are compressed into a block of compressed data. The block of sub-primitive presence indications is subdivided into a plurality of parent regions, each of the parent regions being subdivided into a plurality of child regions. A hierarchical representation of the block of sub-primitive presence indications is determined, wherein for each of one or more parent regions whose child regions all have the same presence state according to the sub-primitive presence indications in the block of sub-primitive presence indications, parent-level data is included in the hierarchical representation to represent the presence state of the parent region without child-level data for the child regions within the parent region being included in the hierarchical representation. The determined hierarchical representation of the block of sub-primitive presence indications is then stored in the block of compressed data.