Setting up the coordinate system

The spherical sketch pad routines work in data coordinates so a data coordinate system must be setup in some way before using these routines or an error will occur.

Setting up the coordinate system consists of two steps:

Set the plot window screen position
Set the data coordinates within the plot window

The plot window screen position is defined in !p.position in normalized coordinates:

      !p.position=[xmn, ymn, xmx, ymx]

!p.position=[0,0,1,1] gives a full screen window.

Data coordinates may be setup simply by doing a plot, but typically this gives different scales in the x and y directions, so spheres will not appear round.

The S1R routine set_isoxy sets equal scaling in both dimensions. The call is:

 set_isoxy, xmn, xmx, ymn, ymx
   xmn, xmx = desired min and max X.        in
   ymn, ymx = desired min and max Y.        in

Several keywords are also available, do set_isoxy,/help for details.

For example, to cover a sphere of radius 1 centered at (0,0) and leave a bit of margin the following call will work:

 set_isoxy, -1.2,1.2,-1.2,1.2

Setting the sphere position and orientation
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