Is useful in topography for "Digital Terrain Modeling" (DTM) by "Triangulated Irregular Network" (TIN) representation (by 3DPOLY SPLINE or BLOCK entities) and editing (modify delete or add) of 3D points and for triangulation isolines (contour lines) color-filled contour map cross sections longitudinal profile 2D entities (Line or PLine) projection over a DTM conversion of a TIN to a regular grid of points and for conversion of existing isolines resulting from maps in points and then in TIN. It exists a modifiable library for codes and BLOCKs. The coordinates the code and the position (in 3DPOLY or SPLINE) of the points can be modified interactively. You can represent the geological stratification resulting from drilling. The triangulation is performed on a convex hull of a set of points or between an external contour and possibly more interior contours. You can calculate the volume 3D area and center of gravity of some bodies limited by 3DFACE entities. You can intersect or divide two triangulations (or two sets of 3dmesh and 3dface entities) or a triangulation by a horizontal plane. DXF files can be loaded or saved. RCAD can also run scripts can be called from other programs and can interpolate a set of 3DFACE entities using quartic triangular patches with G1 continuity. RCAD graphic core distributed together with RTOPO provides OpenGL real-time orbit pan zoom shading lighting and motion path animation.