Enables and sets the different parameters for non grid to grid data mapping.
Syntax:
set dgrid3d {,{<row_size>}{,{<col_size>}{,<norm>}}}
set nodgrid3d
Examples:
set dgrid3d 10,10,2
set dgrid3d ,,4
The first selects a grid of size 10 by 10 to be constructed and the use of L2 norm in the distance computation. The second only modifies the norm to be used to L4.
By default this option is disabled. When enabled, 3d data read from a file is always treaded as a scattered data set. A grid with dimensions derived from a bounding box of the scattered data and size as specified by the row/col_size above is created for plotting and contouring. The grid is equally spaced in x and y while the z value is computed as a weighted average of the scattered points distance to the grid points. The closer the scatter points to a grid point are the more effect they have on that grid point. The third, norm, parameter controls the ``meaning'' of the distance, by specifying the distance norm. This distance computation is optimized for powers of 2 norms, specifically 1, 2, 4, 8, and 16, but any nonnegative integer can be used.
This dgrid3d option is a simple low pass filter that converts scattered data to a grid data set. More sophisticated approaches to this problem exists and should be used as a preprocess to and outside gnuplot if this simple solution is found inadequate.