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 == 0 for each voxel to test silhouette What is the gradient when dealing with volume data? Why does == 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