BVH Compression via Mixed Precision Offsets
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Solution Overview
Problem
Current ray tracing technologies face challenges in efficiently compressing bounding volume hierarchies (BVH) for reduced memory usage and improved traversal performance, particularly in real-time applications, due to high memory requirements and complexity in implementing hierarchical encoding.
Innovation Solution
The proposed solution involves encoding N child bounding boxes of an N-wide BVH node relative to a merged parent bounding box, using higher precision for the parent and lower precision for the children, allowing for reduced memory storage and bandwidth without requiring extra stack space for decompression during traversal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If higher precision is used for parent bounding box and lower precision for child bounding boxes, then memory storage and bandwidth requirements are reduced, but traversal accuracy may be compromised
Solution Approach 1:
The patent applies different precision levels to different parts of the BVH structure: higher precision (e.g., 16-bit floats) is used for parent bounding box coordinates to maintain accurate spatial relationships, while lower precision (e.g., 8-bit integers) is used for child bounding box offsets to reduce memory usage. This local differentiation of quality allows the system to optimize memory storage while preserving sufficient accuracy for ray traversal operations.
2Quantity of substance
If BVH compression is implemented to reduce memory usage, then memory bandwidth is improved, but device complexity increases due to encoding requirements
Solution Approach 1:
The BVH encoding is segmented into distinct components: parent bounding box coordinates are stored with high precision, while child bounding box information is stored as relative offsets with lower precision. This segmentation allows the compression scheme to be applied selectively to different parts of the data structure, reducing overall memory bandwidth requirements while keeping the encoding logic modular and manageable.
Solution Approach 2:
The patent performs preliminary compression of the BVH structure before ray traversal operations. By pre-computing and storing child bounding box positions as offsets from parent bounding boxes, the system prepares the data in a compressed format that reduces memory bandwidth requirements during traversal, at the cost of additional preprocessing complexity.
3Quantity of substance
If reduced precision is used for child bounding boxes, then memory storage is reduced, but intersection testing accuracy may be affected
Solution Approach 1:
The patent changes the precision parameters of child bounding box representations by storing them as lower-precision offsets relative to parent bounding boxes. During intersection testing, these offset values are combined with the high-precision parent coordinates to reconstruct accurate child bounding box positions, thereby maintaining intersection testing reliability while reducing memory storage requirements.
Data Source
AI summary
Apparatus and method for compressing an acceleration data structure such as a bounding volume hierarchy (BVH). For example, one embodiment of a graphics processing apparatus comprises: one or more cores to execute graphics instructions including instructions to perform ray tracing operations; and compression circuitry to compress lowest level nodes of a hierarchical acceleration data structure comprising a plurality of hierarchically arranged nodes, each of the lowest level nodes comprising pointers to leaf data; the compression circuitry to quantize the lowest level nodes to generate quantized lowest level nodes and to store each quantized lowest level node and associated leaf data without the pointers to the leaf data.