Date post: | 13-Dec-2015 |
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High Quality Silhouette Illustration for Texture
Based Volume Rendering, Nagy and Klein
Extracting and Rendering Volume Data Silhouettes
• Problem
• Nagy & Klein Basic Approach
• Critical Analysis
Problem
• Huge datasets
• Noisy datasets
• Need efficient and robust technique
Silhouette Extraction Techniques
• Front-face/Back-face Polygonal models
• Image processing
• Surface angle (lots of pre-processing)
Surface Angle
• Compute gradient at each voxel using first order central differences
• Evaluate <V,G> == 0 for each voxel to test silhouette
• What is the gradient when dealing with volume data?
• Why does <V,G> == 0 give us a silhouette?
Nagy & Klein Approach
• Hybrid of front/back facing & image processing techniques
• Processed on GPU• Identify contour
pixels• Identify silhouette
pixels
Nagy & Klein Approach
• Silhouette broadening performed on CPU
• Apply a Gaussian filter on image using convolution
• Use FFT to perform fast convolution
Results
• Engine dataset• Bonsai tree dataset• Skull dataset
Results
• Engine dataset• Bonsai tree dataset• Skull dataset
Results
• Engine dataset• Bonsai tree dataset• Skull dataset
Analysis
• Extraction is very fast (GPU processing)
• Guarantees silhouette width of one pixel
• Silhouettes are smooth and continuous
• Only extracts silhouette of most external iso-surface
• Cannot reveal any internal details
Analysis
• Volume rendering by nature is meant to reveal internal details