Bounding Volume Hierarchy Rasterization via Lowest Common Ancestor

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Solution Overview

Problem

Current graphics processing methods for ray tracing in computer graphics are inefficient due to the need for traversing the entire acceleration data structure (ADS) to determine ray-primitive intersections, leading to increased computational load and potential errors when determining the correct node for traversal.

Innovation Solution

A method that determines the lowest common ancestor node of two nodes in a hierarchical structure, allowing for more efficient traversal by aligning node indices and identifying a common set of bits to reduce the number of ray intersection tests, thereby accelerating the rasterization of representations to an off-screen render target.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the entire acceleration data structure is traversed to determine ray-primitive intersections, then all possible intersections can be found, but the computational load increases and processing time is extended

Engineering Contradiction:
Improveaccuracy of ray-primitive intersection determinationVSAvoidprocessing speed of ray tracing
Core Design Contradiction:
ReliabilityVSProductivity

Solution Approach 1:

The acceleration data structure is segmented into a hierarchical organization of bounding volumes at multiple levels. Instead of traversing all primitives, the method segments the search space into bounding volumes and traverses only the necessary hierarchy levels, significantly reducing the number of intersection tests while maintaining completeness.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The acceleration data structure is pre-organized into a hierarchical bounding volume hierarchy before ray tracing begins. This preliminary organization allows rays to quickly eliminate large portions of the scene by testing against coarse bounding volumes first, avoiding the need to test every primitive individually during the actual ray tracing process.

Inventive Principle:
Principle #10Preliminary action

2Measurement precision

If traditional methods are used to determine the lowest common ancestor node, then the correct node can be identified, but the computational overhead increases

Engineering Contradiction:
Improveaccuracy of lowest common ancestor node determinationVSAvoidcomputational complexity of node determination
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The mechanical traversal process for finding the lowest common ancestor node is replaced with a bitwise computational operation. By encoding node positions in the hierarchy as bit patterns and using bitwise AND operations, the lowest common ancestor is determined through efficient bit manipulation rather than iterative traversal, reducing computational complexity while maintaining accuracy.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentEP3420537B1Single pass bounding volume hierarchy rasterization
Publication Date: 2020.02.19 QUALCOMM INC
  • EP3420537B1 patent drawingFigure 1
  • EP3420537B1 patent drawingFigure 2
  • EP3420537B1 patent drawingFigure 3

AI summary

A render output unit running on at least one processor may receive a source pixel value to be written to a pixel location in a render target, wherein the source pixel value is associated with a source node in a hierarchical structure. The render output unit may receive a destination pixel value of the pixel location in the render target, wherein the destination pixel value is associated with a destination node in the hierarchical structure. The render output unit may determine a lowest common ancestor node of the source node and the destination node in the hierarchical structure. The render output unit may output a resulting pixel value associated with the lowest common ancestor node of the source node and the destination node to the pixel location in the render target.