Sketcher ConstrainSymmetric

From FreeCAD Documentation
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Sketcher ConstrainSymmetric

Menu location
Sketch → Sketcher constraints → Constrain symmetrical
Workbenches
Sketcher
Default shortcut
S
Introduced in version
-
See also
Sketcher Constraint Parallel

Description

The Sketcher ConstrainSymmetric command defines two selected points to be symmetrical around a given line, i.e., both selected points are constrained to lie on a normal to the line through both points and are constrained to be equidistant from the line. Alternatively it can constrain two points to be symmetric with respect to a third one.

Usage

Select two points (vertexes) in the sketch and a line in the sketch. The selected points and the line will be dark green.

There are several ways to invoke the command:

  • Press the Constrain symmetric button.
  • Select the Sketch → Sketcher constraints → Constrain symmetric option from the menu.
  • introduced in version 0.22: Right-click in the 3D view and select the Constrain symmetric option from the context menu.
  • Use the keyboard shortcut: S.

This will apply the constraint to the selected items.

Note: Before Version 0.19 (see fix [1]), if you want to define a symmetry constraint with respect to a point, the order of the selection is important, depending on if you select the tool at the beginning or at the end.

  • If you click the tool first: select the first point, then the symmetry reference point, and finally the second point.
  • If you click the tool last: select the first point, then the second point, and finally the symmetry reference point.

See the tracker issue #4144, and forum thread.

Scripting

Two points and a symmetry line:

Sketch.addConstraint(Sketcher.Constraint('Symmetric', Line1, PointOfLine1, Line2, PointOfLine2, SymmetryLine))

Two points and a symmetry point:

Sketch.addConstraint(Sketcher.Constraint('Symmetric', Line1, PointOfLine1, Line2, PointOfLine2, LineS, PointOfLineS))

A line and a symmetry point (In the GUI one can select a line and a point, but it uses internally the same form as above, with the two extremities of the same line):

Sketch.addConstraint(Sketcher.Constraint('Symmetric', Line, 1, Line, 2, LineS, PointOfLineS))

The Sketcher scripting page explains the values which can be used for Line1, Line2, LineS, Line, PointOfLine1, PointOfLine2 and PointOfLineS, and contains further examples on how to create constraints from Python scripts.