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A.4.5.28 Poly4 Form

The Poly4 () form is available from the quad position layer control, and draws a quadrilateral defined by the coordinates of its vertices supplied as 4 separate positions. Various options for how it is drawn, such as filled or outlined, are available.

Example Poly4 plot

Example Poly4 plot

Poly4 form configuration panel

Poly4 form configuration panel

Configuration options are:

Shading Mode
See Appendix A.4.6.
Polygon Mode
Defines how the polygon is drawn. Options are
Fast
Determines whether speed is favoured over accuracy when drawing polygons. In some cases unchecking this will give visually better results, and in some cases checking it will speed up plotting. In other cases, the setting will make no difference to either. It may be necessary to unset it when filling polygons that may be re-entrant.
Minimal Size
Defines a threshold size in pixels below which, instead of the shape defined by the polygon coordinates, a replacement marker will be painted instead. If this is set to zero, then only the shape itself will be plotted, which may mean it appears as only a single pixel. By setting a larger value, you can ensure that the position of even small polygons is easily visible, at the expense of giving them an artificial shape and size. This value also defines the size of the replacement markers.
Minimal Shape
Selects the shape of replacement markers that get plotted instead of very small polygons, as controlled by the Minimal Size setting.


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TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page: http://www.starlink.ac.uk/topcat/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@jiscmail.ac.uk