Direct volume rendering: A 3D plotting technique for scientific data

Some of the barriers to the advantages of the direct volume rendering methods are discussed. The direct volume rendering primarily offers flexibility. It can be used to obtain an initial overall view of the data, and by changing transfer function, the data's particular features can be focused. One of the drawbacks to rendering the complete volume is that it might result in information overload. Features of interest can easily become obscured by regions of little interest. One way to remove superfluous regions is to insert clipping planes into the volume. A transfer function is a simple mapping from scalar values to color and opacity. A transfer function is generally represented as a lookup table that can be accessed using scalar values and that uses linear interpolation to represent a continuous range with a finite number of entries. Specifying transfer functions requires a lot of user intervention, because volume rendering is often exploratory.