Ambient Occlusion Computation Using Blurred Volume Approximation
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Solution Overview
Problem
Current methods for simulating ambient occlusion in volume rendering are computationally expensive and restrictive, particularly for real-time applications and transfer function manipulations, as they require lengthy pre-processing times and do not allow for interactive visualization.
Innovation Solution
The method involves computing ambient occlusion terms using blurred volumes with different radii, combining these terms into a composite ambient volume occlusion, and applying this composite occlusion during the volume rendering phase to achieve rapid and interactive rendering without the limitations of existing techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Monte Carlo ray tracing is used to compute ambient occlusion on each surface point, then ambient occlusion accuracy is improved, but computation time increases significantly
Solution Approach 1:
The patent replaces the expensive Monte Carlo ray tracing method with a much cheaper blurred volume approximation. The blurred volume is computed once and can be disposed of or recomputed when needed, providing acceptable ambient occlusion results without the prohibitive computational cost of ray tracing.
Solution Approach 2:
The patent substitutes the mechanical ray tracing process with a mathematical blur operation on pre-computed volume data. This replacement transforms a computationally intensive geometric simulation into a simpler convolution operation that can be performed efficiently.
2Illumination intensity
If vicinity shading pre-processing is performed to achieve ambient occlusion in volume rendering, then image realism is improved, but pre-processing time increases to approximately 1 hour
Solution Approach 1:
The patent performs preliminary computation of a blurred volume that encodes ambient occlusion information. This pre-computed blurred volume can be combined with transfer function manipulations without requiring re-computation of the entire ambient occlusion, enabling interactive adjustments while maintaining realistic lighting effects.
Solution Approach 2:
The patent enables dynamic manipulation of transfer functions after the initial blurred volume computation. Users can interactively adjust transfer functions and immediately see updated results by combining them with the pre-computed blurred volume, providing real-time interactivity that was not possible with traditional vicinity shading methods.
3Illumination intensity
If traditional ambient occlusion methods are used, then lighting realism is improved, but transfer function manipulations require re-computation
Solution Approach 1:
The patent separates the ambient occlusion computation into a distinct blurred volume component that is independent of transfer function choices. This segmentation allows transfer functions to be manipulated freely without affecting the ambient occlusion data, enabling versatile interactions while maintaining realistic lighting.
Solution Approach 2:
The blurred volume serves multiple functions: it provides ambient occlusion for realistic lighting, acts as a reusable data structure for different transfer functions, and enables interactive manipulation. This multi-functionality resolves the contradiction by making the ambient occlusion computation adaptable to various transfer function choices without re-computation.
Data Source
AI summary
A method of direct volume rendering is provided comprising combining ambient occlusion volumes terms from a plurality of different filtered volumes using filters with different radii. During an ambient occlusion computation phase, the method obtains ambient occlusion terms from a plurality of different filtered volumes and, combining the ambient occlusion terms from the plurality of different filtered volumes into a composite ambient volume occlusion. During a subsequent volume rendering phase, data acquired from the subject is processed using the composite ambient volume occlusion to obtain a shaded rendition of an image of the subject.