Sketcher: Constrângere de tangență
|
|
| Menu location |
|---|
| Sketch → Sketcher constraints → Constrain tangent |
| Workbenches |
| Sketcher |
| Default shortcut |
| T |
| Introduced in version |
| - |
| See also |
| Constraint point on object |
Description
Descriere
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.
Usage
Cum se folosește
sunt patru moduri diferite în cae contrângerea poate fi aplicată:
- between two curves (available not for all curves)
- between two endpoints of a curve, making a smooth joint
- between a curve and an endpoint of another curve
- between two curves at user-defined point
Pentru a aplica constrângerile de tangență, trebuie să urmați pașii:
- Select two or three entities in the sketch.
- Invoke the constraint by clicking its icon on the toolbar, or selecting the menu item, or using keyboard shortcut.
Între două curbe (direct tangency)
două curbe vor fi făcute tangente, and the point of tangency will be implicit. This mode is applied if two curves were selected.
Accepted selection:
- line + line, circle, arc, ellipse, arc-of-ellipse
- circle, arc + circle, arc
Dacă nu este acceptată tangența directă între curbele selectate (de exemplu, între un cerc și o elipsă), va fi adăugat un punct de ajutor pentru a schița automat și se va aplica tangența-prin-punct.
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)
În acest mod, punctele finale se fac coincidente, and the joint is made tangent (C1-smooth, or "sharp", depending on the placement of curves before the constraint is applied). Acest mod se aplică atunci când au fost selectate două puncte finale de două curbe.
Accepted selection:
- endpoint of line/arc/arc-of-ellipse + endpoint of line/arc/arc-of-ellipse (i.e., two endpoints of any two curves)
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.
Accepted selection:
- line, circle, arc, ellipse, arc-of-ellipse + endpoint of line/arc/arc-of-ellipse (i.e., any curve + endpoint of any curve)
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.
Accepted selection:
- any line/curve + any line/curve + any point
"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.
Pentru ca constrângerea să funcționeze corect, punctul trebuie să fie pe ambele curbe.So, as the constraint is invoked, the point will be automatically constrained onto both curves (helper constraints will be added, if necessary), and the curves will be forced tangent at the point. These helper constraints are plain regular constraints. They can be added manually, or deleted.
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.
Plasarea punctului înaintea aplicării constrângerii este o sugestie pentru rezolvitor pentru locul unde ar trebui să fie tangența. Cu această constrângere, se pot constrânge două elipse să se atingă reciproc în două locuri.
Script
Tangent Constraint poate fi creată din macros și din consola python folosind următoarele:
# 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))
unde:
- 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 tools: New sketch, Edit sketch, Leave sketch, View sketch, View section, Map sketch to face, Reorient sketch, Validate sketch, Merge sketches, Mirror sketch
- Sketcher geometries: Point, Line by 2 point, Create an arc, Arc, Arc by 3 Point, Create a circle, Circle, Circle by 3 Point, Create a conic, Ellipse by center, Ellipse by 3 points, Arc of ellipse, Arc of hyperbola, Arc of parabola, Create a B-spline, Create B-spline, Create periodic B-pline, Polyline (multiple-point line), Rectangle, Create regular polygon, Triangle, Square, Pentagon, Hexagon, Heptagon, Octagon, Create Regular Polygon, Slot, Fillet, Trimming, Extend, External Geometry, CarbonCopy, Construction Mode
- Sketcher constraints
- Geometric constraints Coincident, Point On Object, Vertical, Horizontal, Parallel, Perpendicular, Tangent, Equal Length, Symmetric, Constrain Block
- Dimensional constraints Lock, Horizontal Distance, Vertical Distance, Distance, Radius, Internal Angle, Snell's Law, Internal Alignment, Toggle reference/driving constraint,
- Sketcher tools Select solver DOFs, Close Shape, Connect Edges, Select Constraints, Select Origin, Select Vertical Axis, Select Horizontal Axis, Select Redundant Constraints, Select Conflicting Constraints, Select Elements Associated with constraints, Show/Hide internal geometry, Symmetry, Clone, Copy, Move, Rectangular Array, Delete All Geometry, Delete All Constraints
- Sketcher B-spline tools Show/Hide B-spline degree, Show/Hide B-spline control polygon, Show/Hide B-spline curvature comb, Show/Hide B-spline knot multiplicity, Convert Geometry to B-spline, Increase degree, Increase knot multiplicity, Decrease knot multiplicity
- Sketcher virtual space Switch Virtual Space
- Installation: Unix, Windows, Mac; Getting started
- Basics: About FreeCAD, Workbenches, Preferences, Document structure, Interface Customization, Properties, Mouse Model; Tutorials
- Workbenches: Arch, Draft, FEM, Image, Inspection, Mesh, OpenSCAD, Part, PartDesign, Path, Plot, Points, Raytracing, Reverse Engineering, Robot, Ship, Sketcher, Spreadsheet, Start, Surface workbench, TechDraw, Test Framework, Web
- Scripting: Introduction to Python, FreeCAD scripting tutorial, FreeCAD Scripting Basics, How to install macros, Gui Command, Units Modules: Builtin modules, Workbench creation, Installing more workbenches Meshes: Mesh Scripting, Mesh Module Parts: The Part Module, Topological data scripting, PythonOCC, Mesh to Part Coin scenegraph: The Coin/Inventor scenegraph, Pivy Qt interface: PySide, Using the FreeCAD GUI, Dialog creation Parametric objects: Scripted objects Other: Code snippets, Line drawing function, Embedding FreeCAD, FreeCAD vector math library, Power users hub, Python, Macros, FreeCAD Scripting Basics, Topological data scripting
