Sketcher CreateBSpline
This documentation is a work in progress. Please don't mark it as translatable since it will change in the next hours and days.
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 Backspace before terminating the input to delete the last control point.
- 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, the knot multiplicity and the control point weight 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, 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
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- Hubs: User hub, Power users hub, Developer hub