15.40.16  3-d_histograms 

A 3-d histogram can be either a plot of mesh data or a  plot  of  "normal"
x,y,z  data.   Mesh  data  is  normally plotted as a "solid".  XYZ data is
plotted as a histogram of X vs Z in the plane determined by  Y.   For  all
3-d  histograms Z must be the dependent variable, and X,Y are independent.
Repeated XYZ plots may be used to build up a series of histograms.

                                   NOTE
Some  lines  may  be  missing from the plot, because of the viewpoint.  If
this happens you may need to: 
     TD:SET THREE RDIST 1000
This moves the viewpoint closer to infinity, but maintans the plot size.

If  the  plot  is  too  large  you may need to adjust the screen or window
distance.
     TD:SET THREE DIST 1000 SCRD 300
Will  reduce  the  size  of  the  plot.   The  size of the plot is roughly
proportional to the ratio of SCRD to DIST.

If you specify color, intensity, or texture it is used for the top side of
the mesh, while the default is used for the bottom.

                                  example
     TD:SET COLOR RED
     TD:SET TEXTURE DOTS
     TD:HISTOGRAM SOLID WHITE
Produces  a  mesh plot with bottom in dotted red lines, while the top side
is drawen in white solid lines.