Bounding Volume Hierarchy Splitting With Implicit Morton Codes
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Solution Overview
Problem
Existing methods for building bounding volume hierarchies (BVHs) in ray tracing are inefficient due to the reliance on explicit Morton codes, which result in limited precision and increased overhead, making it difficult to accurately construct BVHs for complex geometries.
Innovation Solution
A top-down approach for building BVHs that uses implicit Morton codes, where nodes are split along the largest dimension and bounding volumes are updated in a single dimension, allowing for efficient construction of BVHs without the need for atomic operations in every dimension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If explicit Morton codes are used to build BVHs, then the construction process is simplified, but precision is limited and overhead increases
Solution Approach 1:
The patent introduces an intermediary coordinate system transformation process that converts explicit Morton codes into implicit spatial relationships. By using a reference node's bounding box as a mediator, the system translates discrete Morton code values into continuous spatial coordinates, enabling precise geometric calculations while maintaining the simplicity of Morton code ordering.
Solution Approach 2:
The patent transforms the problem from working directly with 1D Morton code values to operating in 3D spatial dimensions. By mapping Morton codes to3D bounding box coordinates through coordinate system transformation, the system gains dimensional information that enables more precise BVH construction while maintaining the computational efficiency of the original Morton code approach.
2Ease of operation
If Morton codes are used for BVH construction, then node ordering is simplified, but computational overhead increases
Solution Approach 1:
The patent performs preliminary coordinate system transformation and bounding box calculation during the BVH construction phase. By pre-computing the spatial relationships and storing transformed coordinates alongside Morton codes, the system eliminates the need for repeated computational overhead during ray tracing operations, amortizing the computational cost to the construction phase only.
3Measurement precision
If bounding volumes are updated in all dimensions, then precision is maintained, but computational complexity increases
Solution Approach 1:
The patent applies local quality by updating bounding volume parameters selectively based on the split dimension. When splitting along a specific axis, only the bounding box parameters related to that dimension are updated, while other dimensions retain their existing values. This localized update approach maintains precision where needed while reducing unnecessary computational complexity in other dimensions.
Data Source
AI summary
A technique for building a bounding volume hierarchy is disclosed. The technique includes for a subject node, selecting a dimension along which to perform a split to form child nodes of the subject node; assigning primitives of the subject node to the child nodes; and updating bounds for the child nodes in a next split dimension and not in the other dimensions.