Volume rendering is a computer graphics technique whereby the object or phenomenon of interest is sampled or subdivided into many cubic building blocks, called voxels (or volume elements.) A voxel is the 3-D counterpart of the 2-D pixel and is a measure of unit volume. Each voxel carries one or more values for some measured or calculated property of the volume (such as intensity values in the case of LSCM data) and is typically represented by a unit cube. The 3-D voxel sets are assembled from multiple 2-D images (such as the LSCM image stack), and are displayed by projecting these images into 2-D pixel space where they are stored in a frame buffer. Volumes rendered in this manner have been likened to a translucent suspension of particles in 3-D space.
In surface rendering, the volumetric data must first be converted into geometric primitives, by a process such as isosurfacing, isocontouring, surface extraction or border following. These primitives (such as polygon meshes or contours) are then rendered for display using conventional geometric rendering techniques.
