BVH Hit Map Traversal for Spatially Local First-Hit Rays
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Solution Overview
Problem
Current ray tracing techniques do not utilize spatial locality for neighboring pixels, leading to inefficient traversal of bounding volume hierarchies (BVHs) and increased computational complexity.
Innovation Solution
Generate a bounding volume hierarchy (BVH) hit map based on pixel coordinates, allowing traversal from non-root nodes to expedite BVH traversal and reduce computational and memory resource usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional ray tracing techniques are used without spatial locality optimization, then the implementation is simple, but the BVH traversal efficiency is poor and computational complexity increases
Solution Approach 1:
The patent pre-computes and stores BVH traversal paths for a set of representative rays during an offline phase. During the online rendering phase, these pre-computed paths are retrieved and reused for similar rays, eliminating the need to re-traverse the entire BVH tree for each ray. This preliminary action significantly speeds up BVH traversal while maintaining implementation simplicity through efficient data structures.
Solution Approach 2:
The patent creates a lookup table or cache that stores pre-computed BVH traversal paths for representative rays. When processing a new ray, the system copies the traversal path from the cache if the ray falls within a spatial neighborhood of a representative ray, rather than performing a complete BVH traversal. This copying approach maintains traversal efficiency while simplifying the overall implementation through direct path reuse.
2Quantity of substance
If spatial locality is not utilized for neighboring pixels, then the processing is straightforward, but memory resource usage increases and bottlenecks occur
Solution Approach 1:
The patent applies different processing strategies to different spatial regions based on their characteristics. For pixels in the same spatial neighborhood as a representative ray, the system uses optimized local traversal paths. For pixels in different neighborhoods, the system performs complete traversals or uses default paths. This local quality differentiation reduces overall memory usage while maintaining high performance for the majority of cases.
Solution Approach 2:
The patent performs complete BVH traversals only for a subset of rays (representative rays) to build the lookup table, while reusing these results for many other rays through spatial locality exploitation. This partial action approach significantly reduces the total number of memory accesses and computational operations required, thereby reducing memory resource usage and eliminating bottlenecks.
3Loss of time
If complete BVH traversal is performed for all rays, then accuracy is maintained, but computational time and resource consumption increase
Solution Approach 1:
The patent uses feedback from analyzing representative rays to optimize the traversal paths stored in the lookup table. By examining which traversal paths are most frequently accessed and which spatial neighborhoods yield the best performance, the system iteratively refines the representative ray selection and path storage strategies. This feedback mechanism ensures that the optimized paths maintain sufficient accuracy while significantly reducing traversal time.
Solution Approach 2:
The patent segments the set of all possible rays into multiple spatial neighborhoods based on their positions and directions. Instead of treating all rays uniformly, the system creates separate lookup tables or path caches for different spatial neighborhoods. This segmentation allows the system to optimize traversal paths for each neighborhood independently, maintaining accuracy for rays in well-represented neighborhoods while reducing time for rays in less critical areas.
Data Source
AI summary
This disclosure provides systems, devices, apparatus, and methods, including computer programs encoded on storage media, for exploiting spatial locality to speed up first-hit ray BVH traversals. A processor may generate a bounding volume hierarchy (BVH) hit map based a set of pixels, where the BVH hit map includes entries indicative of intersection information for a set of rays associated with the set of pixels, and where the BVH hit map corresponds to a BVH. The processor may select an entry from the entries of the BVH hit map based on pixel coordinate information for the set of pixels. The processor may traverse the BVH from a node of the BVH associated with the selected entry.