## Surface plots

The styles splot with lines and splot with surface both generate a surface made from a grid of lines. Solid surfaces can be generated using the style splot with pm3d. Usually the surface is displayed at some convenient viewing angle, such that it clearly represents a 3D surface. See set view (p. ). In this case the X, Y, and Z axes are all visible in the plot. The illusion of 3D is enhanced by choosing hidden line removal or depth-sorted surface elements. See hidden3d (p. ) and the depthorder (p. ) option of set pm3d (p. ). The splot command can also calculate and draw contour lines corresponding to constant Z values. These contour lines may be drawn onto the surface itself, or projected onto the XY plane. See set contour (p. ).