A DEM may be created from any TIN using the Convert | TIN->DEM command in the TIN menu. A resolution (x and y spacing) must be defined and then an interpolation method specified (linear is the default) to interpolate DEM elevations from the TIN. Since a DEM must be rectangular, elevations that are outside of the TIN boundary are given a NODATA value of -9999.
Related Topics:
TIN to Scatter Points
Interpolation Options