Speeding up mesh plots

[Steve Welburn]

I saw that there'd been some discussion earlier in the month about  
how slow mesh plots can be.

An extra option which speeds them up is d3dgrid which sets the number  
of grid lines in each direction:

__gnuplot_set__ dgrid3d 50, 50

means that sombrero(200) only actually has 50 X and Y grid-lines.

It's unlikely that a plot with 100 x 1000 grid-lines is actually  
going to resolve 1000 grid-lines on the screen, so choosing a smaller  
grid means less hidden-line removal, and better performance.

The standard normalization for d3dgrid doesn't seem very good, but  
there are options to change it (2 seems to give reasonable sombrero,  
the default is rather flat).

To switch it off, you can use:

__gnuplot_set__ nodgrid3d


Steve Welburn