Sketcher CreateBSpline: Difference between revisions

Latest revision as of 10:14, 21 April 2024

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Arc of parabola

Periodic B-spline by control points

Sketcher

Menu location
Sketcher CreateBSpline
Sketch → Sketcher geometries → Create B-spline
Workbenches
Sketcher
Default shortcut
G B B
Introduced in version
0.17
See also
Sketcher CreatePeriodicBSpline

Description

The Sketcher CreateBSpline tool creates a B-spline curve from control points. See this page for more information about B-splines.

B-spline curve (white) defined by 5 control points.
The control polygon (green) connects the control points (marked with dark yellow weight circles).
The number 3 (green, without brackets) in the center refers to the degree of the B-spline.
The numbers (1) and (4) (green, in round brackets) refer to the multiplicity of the knot points.
The numbers [1.00] (green, in square brackets) refer to the weights of the control points.

Usage

Notes

Elements of the internal geometry can be deleted. They can be recreated at any time with Sketcher RestoreInternalAlignmentGeometry.
After a B-spline is created, it is possible to define the weight of the control points by changing the radii of the weight circles. The equality constraints on the circles need to be deleted first. The radius constraint is arbitrary, the weight of the control points will be defined by the relative radii of the circles. It works similar to gravity: the bigger a circle is in relation to the others, the more the curve will be attracted to that control point.
The visibility of the degree, the control polygon, the curvature comb, the knot multiplicity and the control point weight can be toggled on/off from the Sketcher visual toolbar.

Limitations

Several constraints are not supported at this time.

Arc of parabola

Periodic B-spline by control points

Sketcher

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

Sketcher geometries: Point, Line, Arc, Arc by 3 points, Circle, Circle by 3 points, Ellipse, Ellipse by 3 points, Arc of ellipse, Arc of hyperbola, Arc of parabola, B-spline by control points, Periodic B-spline by control points, B-spline by knots, Periodic B-spline by knots, Polyline, Rectangle, Centered rectangle, Rounded rectangle, Triangle, Square, Pentagon, Hexagon, Heptagon, Octagon, Regular polygon, Slot, Fillet, Corner-preserving fillet, Trim, Extend, Split, External geometry, Carbon copy, Toggle construction geometry

Sketcher constraints:
- Geometric constraints: Coincident, Point on object, Vertical, Horizontal, Parallel, Perpendicular, Tangent, Equal, Symmetric, Block
- Dimensional constraints: Lock, Horizontal distance, Vertical distance, Distance, Radius or weight, Diameter, Auto radius/diameter, Angle, Refraction (Snell's law)
- Constraint tools: Toggle driving/reference constraint, Activate/deactivate constraint

Sketcher tools: Select unconstrained DoF, Select associated constraints, Select associated geometry, Select redundant constraints, Select conflicting constraints, Show/hide internal geometry, Select origin, Select horizontal axis, Select vertical axis, Symmetry, Clone, Copy, Move, Rectangular array, Remove axes alignment, 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, Show/hide B-spline control point weight, Convert geometry to B-spline, Increase B-spline degree, Decrease B-spline degree, Increase knot multiplicity, Decrease knot multiplicity, Insert knot, Join curves

Sketcher virtual space: Switch virtual space

Additional: Sketcher Dialog, Preferences, Sketcher scripting

User documentation

Getting started
Installation: Download, Windows, Linux, Mac, Additional components, Docker, AppImage, Ubuntu Snap
Basics: About FreeCAD, Interface, Mouse navigation, Selection methods, Object name, Preferences, Workbenches, Document structure, Properties, Help FreeCAD, Donate

Help: Tutorials, Video tutorials
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Addons: Addon Manager, External workbenches, Scripting and macros

Hubs: User hub, Power users hub, Developer hub

@@ Line 1: / Line 1: @@
 <languages/>
 <translate>
+<!--T:10-->
+{{Docnav
+|[[Sketcher_CreateArcOfParabola|Arc of parabola]]
+|[[Sketcher_CreatePeriodicBSpline|Periodic B-spline by control points]]
+|[[Sketcher_Workbench|Sketcher]]
+|IconL=Sketcher_CreateArcOfParabola.svg
+|IconR=Sketcher_CreatePeriodicBSpline.svg
+|IconC=Workbench_Sketcher.svg
+}}
+<!--T:1-->
 {{GuiCommand
 |Name=Sketcher CreateBSpline
+|MenuLocation=Sketch → Sketcher geometries → Create B-spline
-|Icon=Sketcher CreateBSpline.svg
+|Workbenches=[[Sketcher_Workbench|Sketcher]]
-|MenuLocation= Sketch → Sketcher geometries → Create B-spline
+|Shortcut={{KEY|G}} {{KEY|B}} {{KEY|B}}
-|Workbenches= [[Sketcher Workbench|Sketcher]]
 |Version=0.17
-|SeeAlso=[[Sketcher_CreatePeriodicBSpline|Sketcher periodic B-spline]]
+|SeeAlso=[[Sketcher_CreatePeriodicBSpline|Sketcher CreatePeriodicBSpline]]
 }}
-==Description==
+==Description== <!--T:2-->
+<!--T:3-->
-This tool traces an open B-spline curve from its control points.
+The [[Image:Sketcher_CreateBSpline.svg|24px]] [[Sketcher_CreateBSpline|Sketcher CreateBSpline]] tool creates a B-spline curve from control points. See [[B-Splines|this page]] for more information about B-splines.
 </translate>
+[[Image:Sketcher_CreateBSpline_Example.png]]
-[[File:Sketcher B-spline example01.png|none]]
 <translate>
+<!--T:4-->
-''A B-spline curve made from 4 points (in white). Pictured are the control polygon in green (the straight lines connecting the red points), the weight circles in blue and the curvature comb in green. The (3) digit in the centre refers to the degree of the B-spline, and the (4) digits at the ends of the curve refer to their knot multiplicity.''
+{{Caption|B-spline curve (white) defined by 5 control points.<br>
+The control polygon (green) connects the control points (marked with dark yellow weight circles).<br>
+The number 3 (green, without brackets) in the center refers to the [[Sketcher_BSplineIncreaseDegree#Description|degree]] of the B-spline.<br>
+The numbers (1) and (4) (green, in round brackets) refer to the [[Sketcher_BSplineDecreaseKnotMultiplicity#Description|multiplicity]] of the knot points.<br>
+The numbers [1.00] (green, in square brackets) refer to the weights of the control points.}}
+==Usage== <!--T:5-->
-==How to use==
+<!--T:16-->
-# Press the {{KEY|[[File:Sketcher CreateBSpline.svg|24px]] '''Create B-spline'''}} button.
+See also: [[Sketcher_Workbench#Drawing_aids|Drawing aids]].
-# Create a series of points by clicking in the 3D view. While the command is active, the created points are connected with straight lines, and a construction circle is created centred on each point.
-# Right-click to terminate the input and generate the curve.
-# Depending on preferences, the tool may remain active to trace a new curve. Right-click again to exit the command.
-* It is possible to define the weight of the control points by changing the radii of the weight circles. The equality constraints on the circles need to be deleted first. The radius constraint is arbitrary, the weight of the control points will be defined by the relative radii of the circles. It works similar to gravity: the bigger a circle is in relation to the others, the more the curve will be attracted to the control point.
-* The visibility of the control polygon, the curvature comb, the degree and the knot multiplicity can be toggled on/off from the [[Sketcher Workbench#Sketcher B-spline tools|B-spline tools]] toolbar.
-* Check out the other tools in the [[Sketcher Workbench#Sketcher B-spline tools|B-spline tools]] toolbar for more B-spline editing tools.
+<!--T:6-->
-==Limitations==
+# There are several ways to invoke the tool:
+#* Press the {{Button|[[Image:Sketcher_CreateBSpline.svg|16px]] [[Sketcher_CreateBSpline|B-spline by control points]]}} button.
+#* Select the {{MenuCommand|Sketcher → Sketcher geometries → [[Image:Sketcher_CreateBSpline.svg|16px]] Create B-spline}} option from the menu.
+#* Right-click in the [[3D_view|3D view]] and select the {{MenuCommand|[[Image:Sketcher_CreateBSpline.svg|16px]] Create B-spline}} option from the context menu. {{Version|1.0}}
+#* Use the keyboard shortcut: {{KEY|G}} then {{KEY|B}}, then {{KEY|B}}.
+# The cursor changes to a cross with the tool icon.
+# Pick several control points.
+# While the tool is active a small construction circle is created centered on each point.
+# Optionally press {{KEY|D}} before finishing the input to define the degree of the B-spline.
+# Optionally press {{KEY|Backspace}} before finishing the input to delete the last control point.
+# Right-click or press {{KEY|Esc}} to finish the input.
+# The B-spline is created, including a set of internal geometry (weight circles and knot points).
+# If the tool runs in [[Sketcher_Workbench#Continue_modes|continue mode]]:
+## Optionally keep creating B-splines.
+## To finish, right-click or press {{KEY|Esc}}, or start another geometry or constraint creation tool.
+==Notes== <!--T:14-->
-* Many types of constraints are not supported at this time. Only the B-spline's end points can be constrained.
-* [[Sketcher Trimming|Trimming]] and [[Sketcher Extend|extend]] tools are not supported.
+<!--T:15-->
-* The shape of a B-spline curve can only be edited by dragging one of the control points. The knots lying on the curve cannot be selected.
+* Elements of the internal geometry can be deleted. They can be recreated at any time with [[Sketcher_RestoreInternalAlignmentGeometry|Sketcher RestoreInternalAlignmentGeometry]].
+* After a B-spline is created, it is possible to define the weight of the control points by changing the radii of the weight circles. The equality constraints on the circles need to be deleted first. The radius constraint is arbitrary, the weight of the control points will be defined by the relative radii of the circles. It works similar to gravity: the bigger a circle is in relation to the others, the more the curve will be attracted to that control point.
+* The visibility of the [[Sketcher_BSplineDegree|degree]], the [[Sketcher_BSplinePolygon|control polygon]], the [[Sketcher_BSplineComb|curvature comb]], the [[Sketcher_BSplineKnotMultiplicity|knot multiplicity]] and the [[Sketcher_BSplinePoleWeight|control point weight]] can be toggled on/off from the [[Sketcher_Workbench#Sketcher visual|Sketcher visual]] toolbar.
+==Limitations== <!--T:7-->
+<!--T:8-->
+* Several constraints are not supported at this time.
+<!--T:11-->
+{{Docnav
+|[[Sketcher_CreateArcOfParabola|Arc of parabola]]
+|[[Sketcher_CreatePeriodicBSpline|Periodic B-spline by control points]]
+|[[Sketcher_Workbench|Sketcher]]
+|IconL=Sketcher_CreateArcOfParabola.svg
+|IconR=Sketcher_CreatePeriodicBSpline.svg
+|IconC=Workbench_Sketcher.svg
+}}
 </translate>
+{{Sketcher_Tools_navi{{#translation:}}}}
-{{Clear}}
+{{Userdocnavi{{#translation:}}}}