Hardware Tree Traversal Preemption for Bounded Ray Tracing
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Solution Overview
Problem
Conventional computer graphics hardware struggles to perform physically realistic reflections and shadows due to computational challenges in ray tracing, which is computationally intensive and difficult to execute in real time, especially with complex 3D scenes.
Innovation Solution
A hardware-based traversal coprocessor accelerates ray tracing by efficiently traversing acceleration data structures, such as bounding volume hierarchies, to ensure guaranteed forward progress and support programmable timeouts, enabling real-time rendering of high-quality shadows and reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional hardware is used for ray tracing, then computational accuracy for reflections and shadows is maintained, but processing speed becomes too slow for real-time applications
Solution Approach 1:
The patent segments the ray tracing processing into distinct functional units: a traversal coprocessor dedicated to navigating acceleration data structures and a main processor for other computations. This segmentation allows the traversal operations to be accelerated in hardware while keeping the overall system manageable in complexity.
Solution Approach 2:
The traversal coprocessor acts as an intermediary between the main processor and the acceleration data structure. It specialized hardware component that handles the complex tree traversal operations, freeing the main processor and enabling real-time performance.
2Loss of time
If hardware acceleration is added to improve ray tracing speed, then processing time is reduced, but device complexity and manufacturing difficulty increase
Solution Approach 1:
By segmenting the traversal function into a separate coprocessor, the patent creates a modular design that can be manufactured as a distinct unit. This modularity simplifies the manufacturing process compared to integrating traversal acceleration directly into the main GPU architecture.
Solution Approach 2:
The traversal coprocessor is designed to autonomously handle traversal operations without requiring complex control logic from the main processor. It maintains its own execution state and can operate independently, simplifying the overall system design and manufacturing.
3Productivity
If the coprocessor is preempted for other tasks, then processor utilization is improved, but ray tracing progress may be interrupted and quality degraded
Solution Approach 1:
The patent implements preliminary actions by checking whether the coprocessor has made sufficient forward progress before allowing preemption. This ensures that ray tracing operations have reached a stable state before being interrupted, maintaining result quality even when preempted for other tasks.
Solution Approach 2:
The system uses feedback mechanisms to monitor coprocessor progress and make informed preemption decisions. By tracking traversal progress and using this feedback to control preemption, the system balances processor utilization with ray tracing reliability.
Data Source
AI summary
In a ray tracer, to prevent any long-running query from hanging the graphics processing unit, a traversal coprocessor provides a preemption mechanism that will allow rays to stop processing or time out early. The example non-limiting implementations described herein provide such a preemption mechanism, including a forward progress guarantee, and additional programmable timeout options that can be time or cycle based. Those programmable options provide a means for quality of service timing guarantees for applications such as virtual reality (VR) that have strict timing requirements.