High-Quality Silhouette Illustration for Texture-Based Volume Rendering

We present an accurate, interactive silhouette extraction mechanism for texture-based volume rendering. Compared to previous approaches, our system guarantees silhouettes of a user controlled width without any significant preprocessing time. Our visualization pipeline consists of two steps: (a) extraction of silhouettes with a width of one pixel, and (b) image post-processing for broadening of silhouettes. Step (a) is a mixture of objectand image-basedsilhouette extraction models, maximally exploiting the screen resolution. This hybrid approach is neither sensitive to accuracy in gradient representation nor to the precision of the depth-buffer, as in earlier procedures. Step (b) is accomplished via smoothing and applying a threshold to the temporary result obtained in (a). To keep the latter process efficient, we perform fast convolution using FFT. Our silhouette extraction is conceptually similar to the corresponding method for polygonal representations, checking the frontand back facing property of adjacent triangles.