Abstract
In this paper we present the results of an evaluation of different visualization methods for angiogram volumetric data - ray casting, marching cubes, and multi-level partition of unity implicits. There are several options available with ray-casting: isosurface extraction, maximum intensity projection and alpha compositing, each producing fundamentally different results. Different visualization methods are suitable for different needs, so this choice is crucial in diagnosis and decision making processes. We also evaluate visual effects such as ambient occlusion, screen space ambient occlusion, and depth of field. Some visualization methods include transparency, so we address the question of relevancy of this additional visual information. We employ transfer functions to map data values to color and transparency, allowing us to view or hide particular tissues. All the methods presented in this paper were developed using OpenCL, striving for real-time rendering and quality interaction. An evaluation has been conducted to assess the suitability of the visualization methods. Results show superiority of isosurface extraction with ambient occlusion effects. Visual effects may positively or negatively affect perception of depth, motion, and relative positions in space.