Ray Traversal False Positive Reduction in BVH
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Solution Overview
Problem
Current ray tracing technologies face challenges in achieving real-time interactive performance due to high computational complexity and inefficiencies in ray-bounding volume intersections, leading to false positives and performance drops, especially when the ray origin is far from the bounding volume.
Innovation Solution
The implementation of three techniques: Transform Box Test (TBT), Point Degenerate Culling (PDC), and Ray Clipping, which reduce false positive ray-bounding volume intersections by using higher precision math for selected nodes, culling degenerated bounding volumes, and parametrically moving the ray origin to minimize bloat, respectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If lower precision math is used for ray-bounding volume intersection tests, then processing speed increases, but false positive intersections increase
Solution Approach 1:
The patent segments the intersection test process into multiple stages: a fast lower-precision bounding box test followed by a more accurate refined test only for potentially intersecting cases. This segmentation allows most tests to use fast math while ensuring accuracy only when needed, resolving the contradiction between speed and reliability.
Solution Approach 2:
The patent applies different precision levels to different parts of the computation: lower precision is used for the initial bounding box intersection test, while higher precision is applied only to the refined intersection test for cases that potentially intersect. This local quality approach optimizes overall performance while maintaining accuracy where critical.
2Reliability
If ray bloat is increased to reduce false negatives, then watertight guarantees improve, but false positive intersections increase
Solution Approach 1:
The patent performs preliminary classification of bounding volumes before ray traversal, identifying and culling degenerated volumes that would cause false positives. This preliminary action prevents unnecessary traversals while maintaining watertight guarantees for valid bounding volumes, resolving the contradiction between reliability and productivity.
Solution Approach 2:
The patent extracts and removes degenerated bounding volumes from the traversal set through culling operations. By taking out these problematic volumes that would cause false positives, the system maintains accuracy for valid volumes while improving overall performance by eliminating unnecessary processing.
3Measurement precision
If more bounding volume tests are performed to reduce false positives, then intersection accuracy improves, but processing time increases
Solution Approach 1:
The patent applies partial action by performing the more expensive refined intersection test only for a subset of bounding volumes that pass the initial fast test and meet certain criteria. This partial application of high-precision testing achieves necessary accuracy while avoiding the time cost of applying it universally.
Solution Approach 2:
The patent performs preliminary filtering using fast bounding box tests before applying more expensive refined intersection tests. This preliminary action eliminates most non-intersecting cases early, allowing high-precision tests to be applied only when necessary, thus achieving accuracy without excessive time loss.
Data Source
AI summary
Techniques applicable to a ray tracing hardware accelerator for traversing a hierarchical acceleration structure with reduced false positive ray intersections are disclosed. The reduction of false positives may be based upon one or more of selectively performing a secondary higher precision intersection test for a bounding volume, identifying and culling bounding volumes that degenerate to a point, and parametrically clipping rays that exceed certain configured distance thresholds.