Volume Rendering: a process to visualize a volumetric (3-dimensional) dataset via a transfer function.

Dataset: a file containing volumetric data. Nenners requires data to be in a nrrd file format or have a correated nrrd header file (.nhdr).

Transfer Function: defines the color and opacity (opposite of transparency) of each value in a dataset. The transfer function is defined on a 2D domain, value vs. gradient magnitude. The value is along the x axis, and the gradient magnitude is along the y of the transfer function.

Gradient Magnitude: is a local messure of the amount of change. Therefore, magnitude of the gradient estimates the strength of an edge, or inother words, how likely the particular value is an edge.

Parameter File: Nenners requires certain user input and flags, this input can be saved and read through parameter file. If the graphical setup of nenners is used, it will create a parameter file on the fly.

Teem: a image processing and file formating tool. This library is nessary to use take advantage of all of nenners' functionality.