Sketcher CreateBSpline
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Sketcher CreateBSpline |
Menu location |
---|
Sketch → Sketcher geometries → Create B-spline |
Workbenches |
Sketcher |
Default shortcut |
G B B |
Introduced in version |
0.17 |
See also |
Sketcher periodic B-spline |
Description
The Sketcher CreateBSpline tool creates a B-spline curve by control points. (See this page for more info about B-splines.)
A B-spline curve (in white) defined by 4 control points. Pictured are the control polygon in green (the straight lines connecting the control points) and the weight circles in dark yellow. The green digit "3" in the center refers to the degree of the B-spline and the digits "(4)" at the ends of the B-spline refer to their knot multiplicity. The red digit "3" denotes the control point weight which is defined as radius constraint to the control point circle.
Usage
- There are several ways to invoke the tool:
- Press the B-spline by control points button.
- Select the Sketcher → Sketcher geometries → Create B-spline option from the menu.
- Right-click in the 3D view and select the Create B-spline option from the context menu.
- Use the keyboard shortcut: G then B, then B.
- The cursor changes to a white cross with the tool icon.
- Pick several control points.
- While the tool is active a construction circle is created centered on each point.
- Optionally press D before terminating the input to define the degree of the B-spline. introduced in version 0.20
- Optionally press Backspace before terminating the input to delete the last control point. introduced in version 0.20
- Right-click or press Esc to terminate the input.
- The B-spline is created, including a set of internal geometry (weight circles and knot points).
- Optionally deleted one or more elements of this internal geometry. They can be recreated at any time with Sketcher RestoreInternalAlignmentGeometry.
Notes
- 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 the control point.
- The visibility of the degree, the control polygon, the curvature comb, knot multiplicity and control point weights can be toggled on/off from the Sketcher visual toolbar.
- Check out the tools in the B-spline tools toolbar for more B-spline editing tools.
Limitations
- Many types of constraints are not supported at this time.
- The Extend tool is not supported.
- version 0.20 and below: The Split tool is not supported.
- version 0.20 and below: 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.
Sketcher
- General: Create sketch, Edit sketch, Attach sketch, 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, Polyline, Line, Arc, Arc by 3 points, Arc of ellipse, Arc of hyperbola, Arc of parabola, Circle, Circle by 3 points, Ellipse, Ellipse by 3 points, Rectangle, Centered rectangle, Rounded rectangle, Triangle, Square, Pentagon, Hexagon, Heptagon, Octagon, Regular polygon, Slot, Arc slot, B-spline by control points, Periodic B-spline by control points, B-spline by knots, Periodic B-spline by knots, Toggle construction geometry
- Sketcher constraints:
- Dimensional constraints: Dimension, Horizontal distance, Vertical distance, Distance, Auto radius/diameter, Radius, Diameter, Angle, Lock
- Geometric constraints: Coincident (unified), Coincident, Point on object, Horizontal/vertical, Horizontal, Vertical, Parallel, Perpendicular, Tangent or collinear, Equal, Symmetric, Block
- Other constraints: Refraction (Snell's law)
- Constraint tools: Toggle driving/reference constraint, Activate/deactivate constraint
- Sketcher tools: Fillet, Chamfer, Trim, Split, Extend, External geometry, Carbon copy, Select origin, Select horizontal axis, Select vertical axis, Array transform, Polar transform, Scale transform, Offset geometry, Symmetry, Remove axes alignment, Delete all geometry, Delete all constraints
- Sketcher B-spline tools: Convert geometry to B-spline, Increase B-spline degree, Decrease B-spline degree, Increase knot multiplicity, Decrease knot multiplicity, Insert knot, Join curves
- Sketcher visual: Select unconstrained DoF, Select associated constraints, Select associated geometry, Select redundant constraints, Select conflicting constraints, Show/hide circular helper for arcs, 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, Show/hide internal geometry, 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
- Workbenches: Std Base, Assembly, BIM, CAM, Draft, FEM, Inspection, Mesh, OpenSCAD, Part, PartDesign, Points, Reverse Engineering, Robot, Sketcher, Spreadsheet, Surface, TechDraw, Test Framework
- Hubs: User hub, Power users hub, Developer hub