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## Coordinate system conversion

In addition to being able to rotate, scale, and translate plots, the Transform operator can also perform coordinate system conversions. A plot's coordinates can be specified in terms of Cartesian, Cylindrical, or Spherical coordinates (illustrated in figure). Ultimately, when a plot is rendered in the visualization window, its coordinates must be specified in terms of Cartesian coordinates due to the implementation of graphics hardware. If you have a database where the coordinates are not specified in terms of Cartesian coordinates, you can apply the Transform operator to perform a coordinate system transformation so the plot is rendered correctly in the visualization window.

figure shows a model of an airplane that is specified in terms of spherical coordinates. When it is rendered initially, VisIt assumes that the coordinates are Cartesian, which leads to the plot getting stretched and tangled. The Transform operator was then applied to convert the plot's spherical coordinates into Cartesian coordinates, which allows VisIt to draw the plot as it is intended to look.

Figure 71

Figure 72

The Transform operator allows coordinate system transformations between any of the three supported coordinate systems, shown in figure. To pick a coordinate system transformation, you must first pick the coordinate system used for the input geometry. Next, you must pick the desired output coordinate system. In the example shown in figure, the input coordinate system was Spherical and the output coordinate system was Cartesian. Note that if you use the Transform operator to perform a coordinate system transformation then you cannot also perform rotation, scaling, or translation. If you must perform any of those operations, add a second Transform operator to your plots.