Segment-Based Volume Rendering for Real-Time Global Illumination
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Solution Overview
Problem
Existing DVR methods struggle to achieve high frame rates and quality for volume rendering, particularly in AR/VR applications, due to the computational demands of approximating global illumination and the need for precomputation of lighting values, which limits interactive clipping and transfer function updates.
Innovation Solution
A DVR apparatus that subdivides primary rays based on opacities and colors, calculating segment lighting values for each segment, reducing computational efforts and allowing high-quality volume rendering with approximated global illumination at high frame rates, enabling real-time interaction with transfer function definition and clipping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If precomputation of lighting values is used for each voxel, then image quality with global illumination is improved, but frame rate and interactivity are reduced
Solution Approach 1:
The patent divides the volume data into multiple segments along each ray path, computing lighting values for each segment separately. This segmentation allows the system to process only relevant portions of the volume, reducing the computational burden while maintaining image quality. The segments are defined by opacity thresholds, enabling efficient computation of global illumination effects without requiring full precomputation for every voxel.
Solution Approach 2:
The patent performs preliminary computation of opacity values and segment boundaries before computing lighting values. By pre-identifying which segments require lighting computation based on opacity thresholds, the system avoids unnecessary calculations in transparent or low-priority regions, thereby improving frame rate while preserving image quality in important areas.
2Manufacturing precision
If precomputation of lighting values is used for each voxel, then global illumination quality is improved, but interactive clipping and transfer function updates are limited
Solution Approach 1:
The segment-based approach allows the system to update lighting computations only for affected segments when clipping planes or transfer functions change. Instead of recomputing all lighting values, the system identifies and processes only the segments that intersect with modified regions, enabling real-time interactivity while maintaining global illumination quality.
Solution Approach 2:
The patent implements a dynamic computation model where lighting values are computed on-demand for specific segments rather than being statically precomputed for all voxels. This dynamic approach allows the system to adapt to user interactions such as clipping plane adjustments and transfer function changes, providing real-time feedback without sacrificing illumination quality.
3Productivity
If computational efforts are reduced for real-time rendering, then frame rate is improved, but image quality and global illumination approximation suffer
Solution Approach 1:
The patent applies different computation strategies to different segments based on their opacity and visual importance. High-opacity segments that contribute more to the final image receive more accurate lighting computations, while low-opacity segments use simplified calculations. This local quality approach maintains overall image quality while reducing total computational effort, enabling real-time frame rates.
Solution Approach 2:
The system performs partial computation of lighting values by calculating them only for segments that meet certain opacity criteria rather than for all segments. This selective computation approach provides sufficient global illumination effects for visual quality while significantly reducing the computational load to achieve real-time frame rates.
Data Source
AI summary
The invention relates to a direct volume rendering apparatus for volume rendering a three-dimensional image data set. For each primary ray (10) of a plurality of primary rays, which traverse through the three-dimensional image data set and meet a respective pixel of a two-dimensional image in a two-dimensional image plane on which the three-dimensional image data set should be projected, colors and opacities are provided along the primary ray (10). Each primary ray (10) is subdivided into segments I, II, III, IV based on the opacities and/or colors along the respective primary ray (10), wherein, for each segment I, II, III, IV, a segment lighting value in accordance with a predetermined lighting calculation rule is calculated. The colors and segment lighting values are finally projected along the primary rays (10) onto the pixels based on a predetermined projection rule.