Cache-Based 3D Scene Acceleration Structures for Dynamic Ray Tracing
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Solution Overview
Problem
Existing ray tracing methods for rendering 2-D images from 3-D scenes are inefficient for complex scenes with millions of triangles, as they require extensive intersection testing, and existing acceleration structures incur significant overhead in dynamic scenes where objects frequently change.
Innovation Solution
A method for creating a hierarchical spatial subdivision acceleration structure that uses a bounding volume hierarchy or kD-tree, where primitives are categorized by size and alignment, and a cache-based approach is used to efficiently build and update the structure, minimizing floating-point computations and reducing unnecessary intersection tests.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional ray tracing methods are used to test every triangle in the scene, then complete and accurate intersection testing is achieved, but the computation time and resources become intractable for complex scenes with millions of triangles
Solution Approach 1:
The patent divides the 3D scene space into hierarchical spatial regions (bounding volumes organized in trees). Instead of testing every triangle against every ray, the scene is segmented into manageable spatial units that can be selectively tested, reducing the computational complexity from O(n) to O(log n) in the worst case.
Solution Approach 2:
The patent pre-processes the scene into an acceleration structure (bounding volume hierarchy or kD-tree) before ray tracing begins. This preliminary organization of primitives into spatial regions allows during-rendering queries to efficiently skip large portions of the scene that cannot possibly intersect with the current ray, rather than testing all primitives.
2Productivity
If 3-D spatial acceleration structures are used to subdivide space into regions, then ray intersection testing is accelerated, but significant overhead is incurred when objects frequently change in dynamic scenes
Solution Approach 1:
The patent implements dynamic acceleration structures that can adapt to changing scenes. When objects are added, removed, or modified, the system updates only the affected portions of the bounding volume hierarchy or kD-tree rather than rebuilding the entire structure, allowing the acceleration structure to dynamically adjust to scene changes.
Solution Approach 2:
The patent allows the acceleration structure to change its organizational parameters based on scene characteristics. The system can switch between different bounding volume types, adjust hierarchy depth, or modify spatial subdivision strategies based on the density and distribution of primitives, optimizing performance for different dynamic scene conditions.
3Loss of time
If primitives are categorized by size and alignment with axis-aligned bounding boxes, then the acceleration structure build time is reduced to O(n log n), but more complex categorization logic is required
Solution Approach 1:
The patent applies different bounding volume strategies to different primitives based on their local characteristics. Small primitives may use simple axis-aligned bounding boxes, while larger or irregular primitives may use oriented bounding boxes or multiple smaller bounding volumes. This local adaptation optimizes the overall structure without uniformly applying complex logic to all primitives.
Solution Approach 2:
The patent implements selective categorization where only primitives that benefit from detailed categorization are processed with complex logic, while others use simpler methods. The system performs partial categorization based on thresholds for primitive size, shape regularity, or spatial density, avoiding unnecessary complexity for primitives where simple bounding boxes suffice.
Data Source
AI summary
Systems and methods for producing an acceleration structure provide for subdividing a 3-D scene into a plurality of volumetric portions, which have different sizes, each being addressable using a multipart address indicating a location and a relative size of each volumetric portion. A stream of primitives is processed by characterizing each according to one or more criteria, selecting a relative size of volumetric portions for use in bounding the primitive, and finding a set of volumetric portions of that relative size which bound the primitive. A primitive ID is stored in each location of a cache associated with each volumetric portion of the set of volumetric portions. A cache location is selected for eviction, responsive to each cache eviction decision made during the processing. An element of an acceleration structure according to the contents of the evicted cache location is generated, responsive to the evicted cache location.