Fast Volumetric Ray Tracing via Quad-Tree Light Path Organization
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Solution Overview
Problem
Conventional ultra-realistic volume rendering technologies, based on path tracing or ray tracing, face significant limitations in rendering speed when changing transfer functions and window levels, which compromises quality and usability, especially in medical imaging applications.
Innovation Solution
A computer-implemented method using a quad-tree data structure to organize light paths and intensities, allowing for parallel processing and efficient re-computation of path integrals with the Monte Carlo Ray Tracing algorithm, enabling fast window-leveling and transfer function changes without sacrificing image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional path tracing or ray tracing is used for ultra-realistic volume rendering, then image quality is improved, but rendering speed deteriorates when changing transfer functions and window levels
Solution Approach 1:
The patent pre-computes and stores path integrals for multiple transfer functions and window level combinations in a lookup table before rendering. When rendering, the system retrieves pre-computed values from the lookup table based on the current transfer function and window level parameters, eliminating the need for time-consuming real-time path tracing calculations and enabling instant adjustments while maintaining ultra-realistic image quality
Solution Approach 2:
The patent segments the transfer function into multiple discrete levels and pre-computes path integrals for each segment. By dividing the continuous transfer function space into discrete segments and storing results for each, the system can quickly switch between different transfer function configurations by simply retrieving the appropriate pre-computed segment data, significantly accelerating rendering when adjusting transfer functions and window levels
2Ease of operation
If transfer function and window level adjustments are made in real-time, then user interaction and precision windowing are improved, but rendering quality deteriorates due to speed compromises
Solution Approach 1:
The system pre-computes path integrals for a comprehensive set of transfer functions and window level combinations and stores them in a lookup table. This allows users to interactively adjust transfer functions and window levels in real-time with immediate visual feedback, while the pre-computed high-quality data ensures that rendering quality is maintained without compromise despite the interactive speed requirements
3Productivity
If Monte Carlo Ray Tracing is used to trace rays in parallel, then rendering throughput is improved, but computational complexity increases
Solution Approach 1:
The patent performs the computationally intensive Monte Carlo Ray Tracing in parallel during an offline pre-computation phase to generate lookup tables for multiple transfer functions and window levels. By moving the complex computational work to an offline stage, the system achieves high rendering throughput during interactive use while the upfront computational complexity is paid only once during table generation, not during each rendering operation
Data Source
AI summary
A computer-implemented method for performing window-leveling of volumetric ray tracing includes a computer system retrieving a quad-tree data structure organizing a plurality of light paths associated with a volume rendered using a transfer function and one or more window level values. The computer system also receives a user selection of at least one of a new transfer function or new window level values. The volume is rendered by the computer system with the new transfer function or the new window level values using the quad-tree data structure. Then, the computer system synthesizes an image by adding contributions from all of the plurality of light paths according to the quad-tree data structure.