Nurbs Workbench

Die Nurbs Workbench ist eine Sammlung von Werkzeugen zur Bearbeitung von Freiformflächen.

DraftBSpline Editor

GuiDialog to edit the coordinates of the points of a Draft Bspline.

How to use
  1. seelct a Draft BSpline ore a Draft Wire
  2. execute the Method form Menu

Create a Shoe Rib

A full constrainted sketch is created. The outcome is a closed BSpline based on 16 control points. Some of the controlpoints can be configured by changing the values of the constraints Px0, ….

The other controlpoints follow these main entries.

The shoe rib is a specialized version of the cloverleaf sketch model. There are more constraints to get an easier to maintain object.

Constraints
  • tangets forces: How strong the tangents ar forced on the 4 sides
  • width of the base line
  • positions of the main poles
How to use

The method is used inside the shoe editor during initial creation process.

Create a Clover Leaf

The createcloverleaf creates a sketch with a closed Bspline having 16 poles and some extra objects.

This figure can be the startpoint to create faces with a quadrangle or a cloverleaf structure.

At the moment Sketcher BSpline does not support higher multiplicity knots, but there are some tricks to approximate thi features.

The poles can be grouped this way:

  • 4 poles which play the role of more or less sharp corner points (corner poles)
  • any corner pole has two neighbors which lie symmetric to it (helper poles).
  • 4 poles which are used to change the layout of the edges (edge poles)

For the corner poles there is a quadrangle in construction mode. Changing the layout of this quadrangle changes the main layout of the figure.

Some properties
  • Moving a edge pole inside the corner quadrange makes the edge more and more concave.
  • Reducing the distance of two related helper poles makes the corner sharper. To get a real sharp corner the distance must be 0, but this raises an error of the solver, so a distance of 0.001 mm is a good workaround.
  • if two helper poles and the edge pole between them are collinear then the curve will go through the edge pole.
Next steps
  • It is always possible to break some of the constraints and group the poles an other way.
  • For any pole there is a separate weight defined. Using the weight editor the weights can be changed in a next step.
Ressources

Create a Sketch Spline

creates a sketch with a BSpline on base of a Draft BSpline

createsketchspline.py

Distance between two curves

How near two curves are together.

Draw on a Face

Draw interactive a BSpline curve onto a selected face in 3D.

source

generate random points

Create a Loft on selected ribs

Move along a curve

Needle

Template

How to use
Reference

Perspective Transformation of a Spline

transformation of a spline based on a mapping between two quadrangles.

How to use
Reference

Open Spreadsheet

It opens the spreadsheet of a project as separate main window instead of a window inside the mdi area of FreeCAD. This works only for spreadsheets of needle objects. when the sheet is opened methods for editing the models are connecterd to some cells in the spreadsheet.

How to use
  • menu Needle → Open Spreadsheet
Reference

Remove a Knot

Entfernt einen Knoten aus einer BSpline Curve.

Beim Entfernen eines Knoten kann die entstehende Kurve von der ursprünglichen abweichen. Wenn man die Methode für jeden Knoten einzeln ausführt, bekommt man eine Menge von vereinfachten Kurven, aus der man die „beste“ auswählen kann. Die anderen Vereinfachungen werden dann einfach gelöscht.

Weight Editor

The weight editor can change the weights of the poles of a BSpline curve defined in a sketch. The curve must have constraints for each pole with names „Weight 1“, „Weight 2“, … which correspond to the weight circle radius inside the sketch.

The weight editor changes these constraints.

How to use
  • select a Sketcher Bspline
  • run the method from menu Curves → weight editor
Reference

Zebra Tool

It is used to show the curvature on a surface.

How to use
  • run from menu Faces → Zebra Tool
Reference

Helper files

  • miki - dialog framework
  • needle_cmds - commands for the needle editor

Nurbs2

Videos und Bider

Scanner

Image Processing

nurbs.txt · Zuletzt geändert: 2017/06/22 11:05 von freek