Sketcher ConstrainTangent: Difference between revisions
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{{GuiCommand |
{{GuiCommand |
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|Name=Sketcher ConstrainTangent |
|Name=Sketcher ConstrainTangent |
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|MenuLocation=Sketch → Sketcher constraints → Constrain tangent |
|MenuLocation=Sketch → Sketcher constraints → Constrain tangent or collinear |
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|Workbenches=[[Sketcher_Workbench|Sketcher]] |
|Workbenches=[[Sketcher_Workbench|Sketcher]] |
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|Shortcut={{KEY|T}} |
|Shortcut={{KEY|T}} |
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|SeeAlso= |
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|SeeAlso=[[Sketcher_ConstrainPointOnObject|Sketcher Constraint point on object]] |
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}} |
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The [[Image:Sketcher_ConstrainTangent.svg|24px]] [[Sketcher_ConstrainTangent|Sketcher ConstrainTangent]] tool constrains two edges, or an edge and an axis, to be tangent. Lines are treated as infinite, and |
The [[Image:Sketcher_ConstrainTangent.svg|24px]] [[Sketcher_ConstrainTangent|Sketcher ConstrainTangent]] tool constrains two edges, or an edge and an axis, to be tangent. Lines are treated as infinite, and open curves are virtually extended as well. The constraint can also connect two edges, forcing them to be tangent at the joint. If two lines are selected, or a line and the endpoint of another line, the lines are made collinear. |
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==Usage== <!--T:30--> |
==Usage== <!--T:30--> |
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# Do one of the following (optional if the tool will run in [[Sketcher_Workbench#Continue_modes|continue mode]]): |
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See also: [[Sketcher_Workbench#Drawing_aids|Drawing aids]]. |
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# Make sure there is no selection. |
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#* Press the {{Button|[[Image:Sketcher_ConstrainTangent.svg|16px]] [[Sketcher_ConstrainTangent|Constrain tangent or collinear]]}} button. |
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# Do one of the following: |
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# A Tangent constraint is added. If a point and two edges have been selected, up to two [[Sketcher_ConstrainPointOnObject|Point on object constraints]] can also be added. See [[#Between_two_edges_at_point|Examples]]. |
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===Run-once mode=== <!--T:39--> |
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# Do one of the following: |
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#* Select two endpoints belonging to different edges. |
#* Select two endpoints belonging to different edges. |
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#* Select an edge and the endpoint of another edge (in any order). |
#* Select an edge and the endpoint of another edge (in any order). |
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#* Select a point and two edges (idem). |
#* Select a point and two edges (idem). |
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# Invoke the tool as explained above, or with the following additional option: |
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#* |
#* {{Version|1.0}}: Right-click in the [[3D_view|3D view]] and select the {{MenuCommand|[[Image:Sketcher_ConstrainTangent.svg|16px]] Constrain tangent or collinear}} option from the context menu. |
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# A Tangent constraint is added. If a point and two edges have been selected, up to two [[Sketcher_ConstrainPointOnObject|Point on object constraints]] can also be added. See [[#Between_two_edges_at_point|Examples]]. |
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== |
==Examples== <!--T:41--> |
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[[Image:Sketcher ConsraintTangent mode1.png|600px]] |
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===Between two edges=== <!--T:5--> |
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Two curves will be made tangent, and the point of tangency will be implicit. This mode is applied if two curves were selected. |
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[[Image:Sketcher_ConsraintTangent_mode1.png|400px]] |
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'''Accepted selection:''' |
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* line + line, circle, arc, ellipse, arc-of-ellipse |
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* circle, arc + circle, arc |
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If direct tangency between selected curves is not supported (e.g. between a circle and an ellipse), a helper point will be added to sketch automatically, and tangency-via-point will be applied. |
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The two edges are made tangent. If one of the edges is a [[Sketcher_Workbench#Sketcher_CompCreateConic|conic]], a [[Sketcher_CreatePoint|Point object]] that has a [[Sketcher_ConstrainPointOnObject|Point on object constraint]] with both (extended) edges is added. |
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It is not recommended to reconstruct the point of tangency by creating a point and constraining it to lie on both curves. It will work, but the convergence will be seriously slower, jumpier, and will require about twice as many iterations to converge than normal. |
It is not recommended to reconstruct the point of tangency by manually creating a point and constraining it to lie on both curves. It will work, but the convergence will be seriously slower, jumpier, and will require about twice as many iterations to converge than normal. If the point of tangency is needed, select two edges and an existing point instead. |
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===Between two endpoints |
===Between two endpoints=== <!--T:9--> |
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[[Image:Sketcher ConsraintTangent mode2.png|600px]] |
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</translate> |
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[[Image:Sketcher_ConsraintTangent_mode2.png|400px]] |
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In this mode, the endpoints are made coincident, and the joint is made tangent (C1-smooth, or "sharp", depending on the placement of curves before the constraint is applied). This mode is applied when two endpoints of two curves were selected. If you want this kind of tangency you must not use concidence plus the tangency between the curves/lines. The solver cannot create stable solutions for this combination and replaces the constraints appropriately. |
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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. |
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'''Accepted selection:''' |
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* endpoint of line/arc/arc-of-ellipse + endpoint of line/arc/arc-of-ellipse (i.e., two endpoints of any two curves) |
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===Between |
===Between edge and endpoint=== <!--T:12--> |
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[[Image:Sketcher ConsraintTangent mode3.png|600px]] |
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[[Image:Sketcher_ConsraintTangent_mode3.png|400px]] |
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The endpoint of one edge is constrained to lie on the other edge, and the edges are made tangent at that point. |
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===Between two edges at point=== <!--T:15--> |
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'''Accepted selection:''' |
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* line, circle, arc, ellipse, arc-of-ellipse + endpoint of line/arc/arc-of-ellipse (i.e., any curve + endpoint of any curve) |
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</translate> |
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[[Image:Sketcher_ConsraintTangent_mode4.png|400px]] |
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===Between two curves at point (tangent-via-point) (v0.15)=== <!--T:15--> |
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<translate> |
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[[Image:Sketcher ConsraintTangent mode4.png|600px]] |
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The two edges are made tangent at a given point. The point can be any point, e.g. the center of a circle, the endpoint of an edge, or the origin, it can belong to one of the edges, and it can also be a [[Sketcher_CreatePoint|Point object]]. If required [[Sketcher_ConstrainPointOnObject|Point on object constraint(s)]] are added to ensure the point lies on both (extended) edges. These additional constraints are called [[Sketcher_helper_constraint|helper constraints]]. |
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In this mode, two curves are made tangent, and the point of tangency is tracked. This mode is applied when two curves and a point were selected. |
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'''Accepted selection:''' |
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* any line/curve + any line/curve + any point |
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"Any point" can be a lone point, or a point of something, e.g. a center of a circle, an endpoint of an arc, or the origin. |
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For the constraint to work correctly, the point must be on both curves. So, as the constraint is invoked, the point will be automatically constrained onto both curves ([[Sketcher_helper_constraint|helper constraints]] will be added, if necessary), and the curves will be forced tangent at the point. These [[Sketcher_helper_constraint|helper constraints]] are plain regular constraints. They can be added manually, or deleted. |
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Compared to direct tangency, this constraint is slower, because there are more degrees of freedom involved, but if the point of tangency is needed, it is |
Compared to direct tangency, this constraint is slower, because there are more degrees of freedom involved, but if the point of tangency is needed, it is recommended because it offers better convergence. |
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===Between two lines=== <!--T:32--> |
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The placement of the point before the constraint is applied is a hint for the solver for where the tangency should be. With this constraint, one can constrain two ellipses to touch each other in two places. |
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===Between two lines (collinear)=== <!--T:32--> |
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The two lines are made collinear. |
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'''Accepted selection:''' |
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* any line/vertex + any line/vertex |
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==Scripting== <!--T:21--> |
==Scripting== <!--T:21--> |
Latest revision as of 15:01, 23 April 2024
Sketcher ConstrainTangent |
Menu location |
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Sketch → Sketcher constraints → Constrain tangent or collinear |
Workbenches |
Sketcher |
Default shortcut |
T |
Introduced in version |
- |
See also |
None |
Description
The Sketcher ConstrainTangent tool constrains two edges, or an edge and an axis, to be tangent. Lines are treated as infinite, and open curves are virtually extended as well. The constraint can also connect two edges, forcing them to be tangent at the joint. If two lines are selected, or a line and the endpoint of another line, the lines are made collinear.
Usage
See also: Drawing aids.
Continue mode
- Make sure there is no selection.
- 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.
- The cursor changes to a cross with the tool icon.
- 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).
- 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.
- Optionally keep creating constraints.
- To finish, right-click or press Esc, or start another geometry or constraint creation tool.
Run-once mode
- 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).
- Invoke the tool as explained above, or with the following additional option:
- introduced in version 1.0: Right-click in the 3D view and select the Constrain tangent or collinear option from the context menu.
- 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.
Examples
Between two edges
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.
It is not recommended to reconstruct the point of tangency by manually creating a point and constraining it to lie on both curves. It will work, but the convergence will be seriously slower, jumpier, and will require about twice as many iterations to converge than normal. If the point of tangency is needed, select two edges and an existing point instead.
Between two endpoints
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.
Between edge and endpoint
The endpoint of one edge is constrained to lie on the other edge, and the edges are made tangent at that point.
Between two edges at point
The two edges are made tangent at a given point. The point can be any point, e.g. the center of a circle, the endpoint of an edge, or the origin, it can belong to one of the edges, and it can also be a Point object. If required Point on object constraint(s) are added to ensure the point lies on both (extended) edges. These additional constraints are called helper constraints.
Compared to direct tangency, this constraint is slower, because there are more degrees of freedom involved, but if the point of tangency is needed, it is recommended because it offers better convergence.
Between two lines
The two lines are made collinear.
Scripting
Tangent Constraint can be created from macros and from the Python console by using the following:
# direct tangency
Sketch.addConstraint(Sketcher.Constraint('Tangent',icurve1,icurve2))
# point-to-point tangency
Sketch.addConstraint(Sketcher.Constraint('Tangent',icurve1,pointpos1,icurve2,pointpos2))
# point-to-curve tangency
Sketch.addConstraint(Sketcher.Constraint('Tangent',icurve1,pointpos1,icurve2))
# tangent-via-point (plain constraint, helpers are not added automatically)
Sketch.addConstraint(Sketcher.Constraint('TangentViaPoint',icurve1,icurve2,geoidpoint,pointpos))
where:
Sketch
is a sketch objecticurve1
,icurve2
are two integers identifying the curves to be made tangent. The integers are indexes in the sketch (the value, returned bySketch.addGeometry
).pointpos1
,pointpos2
should be 1 for start point and 2 for end point.geoidpoint
andpointpos
inTangentViaPoint
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.
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