Ray Tracing Instance Transform Cache for Faster Intersection Testing
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Solution Overview
Problem
Ray tracing systems face challenges in achieving real-time rendering on devices with tight constraints on silicon area, cost, and power consumption, such as mobile devices, due to high processing requirements and inefficient intersection testing with current acceleration structures.
Innovation Solution
A hierarchical acceleration structure with instance transforms is used, where each lower level node has a defined relationship to an upper level node, and an instance transform cache stores these transforms for efficient retrieval during intersection testing, reducing memory access overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hierarchical acceleration structures with instance transforms are used, then intersection testing efficiency is improved, but memory access overhead increases
Solution Approach 1:
The patent pre-calculates and stores instance transforms in a cache structure before intersection testing begins. This preliminary action allows the transforms to be readily available during ray tracing operations, eliminating the need for real-time calculation and reducing memory access overhead during actual intersection testing.
Solution Approach 2:
The patent creates a cached copy of instance transforms that can be reused across multiple intersection testing operations. Instead of accessing original transform data repeatedly from main memory, the system uses these cached copies stored in a specialized memory structure, reducing memory access time and overhead.
2Manufacturing precision
If ray tracing is implemented on mobile devices, then photorealistic rendering is achieved, but processing power requirements exceed device capabilities
Solution Approach 1:
The patent segments the ray tracing processing into distinct stages: coherency gathering, intersection testing, and shading. Each stage is optimized independently with specialized hardware units, allowing mobile devices to perform photorealistic rendering by breaking down the computationally intensive task into manageable segments that can be executed efficiently on constrained hardware.
Solution Approach 2:
The patent changes the processing parameters by organizing rays into coherent groups based on spatial and temporal relationships. This reorganization allows the system to process multiple rays together using shared instance transforms from the cache, reducing the total number of operations required and lowering power consumption while maintaining rendering quality.
3Productivity
If instance transforms are cached for coherency gathering, then processing efficiency is improved, but silicon area increases
Solution Approach 1:
The patent implements a nested memory structure where the instance transform cache is organized hierarchically with smaller, frequently accessed transforms stored in faster, closer memory locations. This nested arrangement allows the system to achieve high processing efficiency by accessing critical transforms quickly while using less total silicon area compared to a flat, uniform cache structure.
Data Source
AI summary
A system and method for coherency gathering for rays in a ray tracing system. The ray tracing system uses a hierarchical acceleration structure comprising a plurality of nodes including upper level nodes and lower level nodes. For each instance where one of the lower level nodes is a child of one of the upper level nodes, an instance transform is defined, specifying the relationship between a first coordinate system of the upper level node and the second coordinate system for that instance of the lower level node. The system provides an instance transform cache for storing a plurality of these instance transforms while conducting intersection testing.