Ray Tracing Hardware with Alternate World Space Transforms
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Solution Overview
Problem
Ray tracing in computer graphics is computationally challenging due to the need to analyze millions of light rays interacting with complex 3D scenes, leading to inefficiencies in real-time rendering, especially with traditional axis-aligned bounding boxes (AABBs) that do not fit the geometry well, resulting in false hits and wasted traversal steps.
Innovation Solution
The introduction of an alternate world space transformation for bounding volume hierarchies (BVHs) that allows for more efficient ray tracing by aligning axis-aligned bounding boxes (AABBs) more tightly with objects, reducing false positives through affine transforms such as rotation, dilation, and scaling, and enabling hardware-accelerated traversal of acceleration structures with multiple coordinate spaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional axis-aligned bounding boxes (AABBs) are used for ray tracing, then the bounding volume hierarchy structure is simple and easy to implement, but the bounding boxes do not fit the geometry well resulting in false hits and wasted traversal steps
Solution Approach 1:
The patent applies parameter changes by transforming the coordinate space of bounding boxes from the default world space to alternative world spaces (such as rotated or scaled coordinate systems). This changes the orientation and scaling parameters of the bounding boxes to better align with the geometry they enclose, reducing false hits during ray tracing while maintaining the simplicity of the BVH structure.
Solution Approach 2:
The patent introduces dynamic coordinate space transformations where the world space can be alternated between different transformations (e.g., identity transformation for default world space, rotated transformations for optimized bounding box alignment). This dynamic switching allows the system to adapt the coordinate space based on the specific rendering scene and object orientation, optimizing ray tracing performance when needed.
2Productivity
If alternative world space transformations are applied to align bounding boxes with geometry, then false hits are reduced and traversal performance improves, but the hardware acceleration complexity increases due to multiple coordinate spaces
Solution Approach 1:
The patent segments the world space into multiple alternative coordinate spaces (e.g., default world space, rotated world space, scaled world space). Each coordinate space can be independently transformed and applied to specific bounding volume hierarchies or objects. This segmentation allows the hardware to manage multiple coordinate spaces in parallel, reducing the complexity burden on any single hardware component while maintaining overall rendering performance.
Solution Approach 2:
The patent introduces coordinate space transformation matrices as intermediary elements that bridge the default world space and alternative world spaces. These transformation matrices act as mediators that can be pre-computed and stored in hardware lookup tables or memory, allowing the hardware acceleration unit to efficiently apply transformations without complex real-time calculations. The intermediary transformation layer simplifies the hardware structure by providing a standardized interface for coordinate space conversion.
3Manufacturing precision
If millions of light rays are analyzed for real-time rendering, then cinematic-quality rendering is achieved, but computational complexity and processing time increase significantly
Solution Approach 1:
The patent applies preliminary action by pre-computing and pre-organizing bounding volume hierarchies in alternative coordinate spaces before the actual ray tracing process. The coordinate space transformations and bounding box alignments are prepared in advance, allowing the hardware to directly traverse optimized BVH structures during rendering without performing complex transformations in real-time. This preliminary preparation significantly reduces processing time while maintaining cinematic-quality rendering.
Solution Approach 2:
The patent creates copies of the bounding volume hierarchy in multiple alternative coordinate spaces simultaneously. Instead of transforming the same BVH structure repeatedly during rendering, the system maintains parallel copies of the BVH organized in different coordinate spaces. This copying approach allows the hardware to quickly select and traverse the appropriate coordinate space copy based on the current rendering requirements, dramatically reducing processing time for analyzing millions of light rays.
Data Source
AI summary
Enhanced techniques applicable to a ray tracing hardware accelerator for traversing a hierarchical acceleration structure are disclosed. The traversal efficiency of such hardware accelerators are improved, for example, by transforming a ray, in hardware, from the ray's coordinate space to two or more coordinate spaces at respective points in traversing the hierarchical acceleration structure. In one example, the hardware accelerator is configured to transform a ray, received from a processor, from the world space to at least one alternate world space and then to an object space in hardware before a corresponding ray-primitive intersection results are returned to the processor. The techniques disclosed herein facilitate the use of additional coordinate spaces to orient acceleration structures in a manner that more efficiently approximate the space occupied by the underlying primitives being ray-traced.