splot surfaces

splot can display a surface as a collection of points, or by connecting those points. As with plot, the points may be read from a data file or result from evaluation of a function at specified intervals, see set isosamples. The surface may be approximated by connecting the points with straight line segments, see set surface, in which case the surface can be made opaque with set hidden3d. The orientation from which the 3d surface is viewed can be changed with set view.

Additionally, for points in a grid format, splot can interpolate points having a common amplitude (see set contour) and can then connect those new points to display contour lines, either directly with straight-line segments or smoothed lines (see set cntrparam). Functions are already evaluated in a grid format, determined by set isosamples and set samples, while file data must either be in a grid format, as described in data-file, or be used to generate a grid (see set dgrid3d).

Contour lines may be displayed either on the surface or projected onto the base. The base projections of the contour lines may be written to a file, and then read with plot, to take advantage of plot's additional formatting capabilities.