Vazba Bod na bod
Constraint PointOnPoint |
Umístění Menu |
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Sketch → Sketcher constraints → Constrain coincident |
Pracovní stoly |
Náčrt |
Výchozí zástupce |
C |
Představen ve verzi |
- |
Viz také |
Constraint Lock, Vazba Bod na objekt |
Description
Popis
Vytváří vazbu totožnosti na vybrané položce.
Tento vazbový nástroj vezme dva body jako své argumenty a slouží k tomu, že je udělá totožné. (Znamená to, že je udělá jako-jeden-bod).
V praxi je tento nástroj užitečný když je např. mezera mezi dvěma koncovými body přímek, které mají být spojeny - vazba totožnosti na jejich koncové body tuto mezeru uzavře.
Usage
Použití
Jak je uvedeno výše, tento nástroj přijímá dva argumenty - oba jsou to body.
- Nejdříve je nutné vysvítit dva různé body. (Připomínám, že to nebude fungovat jestli se např. pokusíte vybrat počáteční a koncový bod jedné přímky).
- Vysvícení nakreslených položek dosáhnete posunem myši nad položku a kliknutím levým tlačítkem myši.
- Vysvícená položka změní barvu na zelenou.
- následující položky mohou být vysvíceny opakováním výše uvedeného postupu POZNÁMKA: není potřeba zároveň držet stisknutou nějakou další klávesu, jako např. CTRL, abychom dosáhli vícenásobného výběru položek na výkrese.
- Jakmile máte vybrány dva body, kliknutím levým tlačítkem myši na vazbu 'BodNaBod' zajistí, že se body stanou totožné a jsou nahrazeny jedním bodem.
POZNÁMKA: Kvůli nastavení totožnosti bodů, musí FreeCAD nutně posunout jeden nebo oba původní body.
Note: In order to make two points coincident, FreeCAD must out of necessity move one (or both) of the original points.
Alternatives to Coincident constraint
The two constrained items of a Coincident constraint must be start point or end point vertices, or center points of arcs, circles or ellipses. Some combinations which are not possible with a coincident constraint can be emulated using other constraints:
- The Symmetric constraint can be used to place a start point, end point or center point on the midpoint of a straight line.
- A midpoint-to-midpoint placement of two straight lines can be achieved by creating a new Point and using two Symmetric constraints so that it lies on the midpoint of both lines.
- A vertex can be constrained to lie along an edge using a PointOnObject constraint. Note that with this constraint, the point can lie anywhere on the full extension of a segment or curve (i.e. also before the start point or beyond the end point).
- A collinear placement of two straight lines can be obtained by applying a Tangent constraint to them, or by combining a PointOnObject constraint and a Parallel constraint.
- Two edges can be made identical by using two Coincident constraints, one for each pair of extremities.
- Two circles can be made identical by using a Coincident constraint to merge the centers, and applying an Equal constraint to their edges. For arcs, this will ensure both arcs are part of the same circle, while allowing them to have different start and end points.
Scripting
The constraint can be created from macros and from the python console by using the following command:
Sketch.addConstraint(Sketcher.Constraint('Coincident',LineFixed,PointOfLineFixed,LineMoving,PointOfLineMoving))
where :
Sketch
is a sketch objectLineFixed
is the number of the line, that will not move by applying the constraintPointOfLineFixed
indicates which vertex ofLineFixed
has to fulfill the constraintLineMoving
is the number of the line, that will move by applying the constraintPointOfLineMoving
indicates which vertex ofLineMoving
has to fulfill the constraint
As the names LineFixed
and LineMoving
indicate, if both constrained vertices are free to move in any direction, the first one (first to be selected in the Gui) will remain fixed and the other one will move. In the presence of existing constraints, however, both edges may move.
The Scripting Sketcher constraints in Python page explains the values which can be used for LineFixed
, PointOfLineFixed
, LineMoving
and PointOfLineMoving
, and contains further examples on how to create constraints from Python scripts.
- General: Create sketch, Edit sketch, Map sketch to face, Reorient sketch, Validate sketch, Merge sketches, Mirror sketch, Leave sketch, View sketch, View section, Toggle grid, Toggle snap, Configure rendering order, Stop operation
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- Additional: Sketcher Dialog, Preferences, Sketcher scripting
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