NVIZ is a GRASS tool used for viewing data surfaces in three dimensions. It evolved from the earlier GRASS program SG3d.
Developers emphasized on the ease and speed of viewer positioning and provided flexibility for using a wide range of data. A low resolution surface or wire grid (optional) provides real-time viewer positioning capabilities. Similarly, a lighting "model" provides real-time feedback as the user adjusts lighting. Grid and polygon resolution controls allow the user to further refine drawing speed and detail as needed. Continuous scaling of elevation provides the ability to use various data types for the vertical dimension.