Isosurface

This 3D plot style requires a populated voxel grid (see set vgrid, vfill). Linear interpolation of voxel grid values is used to estimate fractional grid coordinates corresponding to the requested isolevel. These points are then used to generate a tessellated surface. The facets making up the surface are rendered as pm3d polygons, so the surface coloring, transparency, and border properties are controlled by set pm3d. In general the surface is easier to interpret visually if facets are given a thin border that is darker than the fill color. By default the tessellation uses a mixture of quadrangles and triangles. To use triangle only, see set isosurface. Example:

set style fill solid 0.3
set pm3d depthorder border lc "blue" lw 0.2
splot $helix with isosurface level 10 fc "cyan"