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#### A.4.5.30 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

Poly4 form configuration panel

Configuration options are:

Shading Mode
  See Appendix A.4.6.
Polygon Mode
  Defines how the polygon is drawn. Options are
  - `outline`: draws a line round the outside of the polygon
  - `fill`: fills the interior of the polygon
  - `cross`: draws a line round the outside of the polygon and lines between all the vertices
Thickness
  Controls the line thickness used when drawing polygons. Zero, the default value, means a 1-pixel-wide line is used. Larger values make drawn lines thicker, but note changing this value will not affect all shapes, for instance filled rectangles contain no line drawings.
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