In ANSIG, a spectrum is viewed as 2D planes or projections of 2D planes. Contours can be computed "on the fly", or the contours can be loaded from precomputed contour files. If the spectrum is a 3D or 4D spectrum, then it is possible to interactively move through the dimension(s) orthogonal to the viewed plane (the so-called non-plane dimensions) with the help of scroll bars at the side of the graphics window. The same scroll bars allow interactive and quick change of how many 2D planes one views at any one time, i.e. how large a chunk of the complete 3D or 4D matrix is projected onto the viewed 2D plane. Any 2D view (or plane) out of a 3D or 4D spectrum can be displayed. It is possible to have several graphics windows open at the same time, and to display different views and different regions of the spectra in each window.
The peak-picking and assignment of crosspeaks in the spectra is done interactively by the user. The assignment data base is updated automatically by the ANSIG program after each change the user makes to the assignment data. The current assignment table and NOE list are always available, and always reflects the current state of the assignment. The NOE list can be output in different formats for use with other programs for the determination of 3D structure.
The ANSIG program allows the definition and use of command macros. The program also contains a programmable interface (the AL language) which is much more powerful than ordinary macros, and makes it possible to write entire procedures to perform data analysis or other operations, including semi-automated assignment algorithms.
The ANSIG program runs on Silicon Graphics workstations. The program will run on machines with low-end graphics (8 bit planes), and is not dependent on high-end hardware such as Z-buffers. ANSIG uses only the mouse and the keyboard as peripheral devices. The limiting factor as far as the interactive graphics is concerned is the number of contour line coordinates loaded to the windows. If the graphics becomes slow, then the amount of contour lines in the windows should be reduced.