Sketcher: Constrângere de tangență

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This page is a translated version of the page Sketcher ConstrainTangent and the translation is 7% complete.
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Sketcher ConstrainTangent

Menu location
Sketch → Sketcher constraints → Constrain tangent
Default shortcut
Introduced in version
See also
Constraint point on object



Tangent Constraint makes two curves to touch each other (be tangent). Lines are treated infinite, and arcs are treated as full circles/ellipses. The constraint is also capable of connecting two curves, forcing them tangent at the joint, thus making the joint smooth.


See also: Drawing aids.

Continue mode

  1. Make sure there is no selection.
  2. There are several ways to invoke the tool:
    • Press the Constrain tangent or collinear button.
    • Select the Sketch → Sketcher constraints → Constrain tangent or collinear option from the menu.
    • introduced in version 1.0: Right-click in the 3D view and select the Constrain → Constrain tangent or collinear option from the context menu.
    • Use the keyboard shortcut: T.
  3. The cursor changes to a cross with the tool icon.
  4. Do one of the following:
    • Select two edges. The edges can be any edge except a B-spline.
    • Select a point and two edges (in that order).
    • Select an edge, a point and another edge (idem).
  5. A Tangent constraint is added. If a point and two edges have been selected, up to two Point on object constraints can also be added. See Examples.
  6. Optionally keep creating constraints.
  7. To finish, right-click or press Esc, or start another geometry or constraint creation tool.

Run-once mode

  1. Do one of the following:
    • Select two edges (see above).
    • Select two endpoints belonging to different edges.
    • Select an edge and the endpoint of another edge (in any order).
    • Select a point and two edges (idem).
  2. Invoke the tool as explained above, or with the following additional option:
  3. A Tangent constraint is added. If a point and two edges have been selected, up to two Point on object constraints can also be added. See Examples.


Între două curbe (direct tangency)

The two edges are made tangent. If one of the edges is a conic, a Point object that has a Point on object constraint with both (extended) edges is added.

Nu se recomandă reconstruirea punctului de tangență prin crearea unui punct și constrângerea lui de a se afla pe ambele curbe. It will work, but the convergence will be seriously slower, jumpier, and will require about twice as many iterations to converge than normal. Use other modes of this constraint if the point of tangency is needed.

Între două puncte finale (point-to-point tangency)

The endpoints are made coincident, and the angle between the edges at that point is set to 180° (smooth joint) or 0° (sharp joint), depending on the placement of the edges before the constraint is applied.

Între curbă și punct final (point-to-curve tangency)

În acest mod, un punct final al unei curbe este constrâns să stea pe cealaltă curbă, and the curves are forced tangent at the point. This mode is applied when a curve and an endpoint of another curve were selected.

Între două curbe la punct (tangent-via-point) (v0.15)

În acest mod, două curbe sunt tangente și punctul de tangență este urmărit. Acest mod se aplică atunci când au fost selectate două curbe și un punct.

În comparație cu tangența directă, această constrângere este mai lentă, deoarece există mai multe grade de libertate implicate, dar dacă este necesar punctul de tangență, acesta este modul recomandat deoarece oferă o convergență mai bună comparativ cu tangența directă + punct pe două curbe.

Between two lines

The two lines are made collinear.


Tangent Constraint poate fi creată din macros și din consola python folosind următoarele:

# direct tangency

# point-to-point tangency

# point-to-curve tangency

# tangent-via-point (plain constraint, helpers are not added automatically)


  • Sketch is a sketch object
  • icurve1, icurve2 are two integers identifying the curves to be made tangent. The integers are indexes in the sketch (the value, returned by Sketch.addGeometry).
  • pointpos1, pointpos2 should be 1 for start point and 2 for end point.
  • geoidpoint and pointpos in TangentViaPoint are the indexes specifying the point of tangency.

The Sketcher scripting page explains the values which can be used for incurve1, incurve2, pointpos1, pointpos2, geoidpoint and pointpos and contains further examples on how to create constraints from Python scripts.