Classification and Survey of Algorithms for Volume Viewing

c s The task of the rendering process is to display the primitives used to represent the 3D volumetri cene onto a 2D screen. Rendering is composed of a viewing process which is the subject of this paper, b and the shading process. The projection process determines, for each screen pixel, which objects are seen y the sight ray cast from this pixel into the scene. The viewing algorithm is heavily dependent on the e e display primitives used to represent the volume and whether volume rendering or surface rendering ar mployed. Conventional viewing algorithms and graphics engines can be utilized to display geometric d primitives, typically employing surface rendering. However, when volume primitives are displayed irectly, a special volume viewing algorithm should be employed. This algorithm should capture the conp tents of the voxels on the surface as well as the inside of the volumetric object being visualized. This aper surveys and compares previous work in the field of direct volume viewing. We describe methods c for accelerating volume viewing, parallel volume viewing algorithms, and special purpose hardware. We onclude by surveying recent method for rendering intermixed volume-and-surface datasets and algorithms for volume viewing of various types of irregular grids.