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IDProjectCategoryView StatusLast Update
0000895FreeCADFeaturepublic2017-03-27 08:28
Reportershoogen Assigned Towmayer  
Status closedResolutionfixed 
Product Version0.12 
Fixed in Version0.14 
Summary0000895: Part.BSplineCurve: allow to set degree and mutliplicites when calling constructor.
DescriptionCurrently the constructor creats a curve with the degree of 1. This will require the user to use removeKnot() to decrease the multiplicities to get a uniform curve (for degrees >1).
Adjusting degree, multiplicites on an existing curve is requies a lot of knowledge about NURBS and OCCT.
possible fix:
Expose the constructor with all parameters
FreeCAD Information


related to 0000337 acknowledged File formats add support for Rhino3D files 
related to 0002253 closedyorik File formats add support for Rhino3D files 



2012-12-01 09:23

developer   ~0002605

Last edited: 2012-12-01 09:25

as removeKnot does not work on the first and last Knot of a periodic curve, there is currently no way to decrease the multiplicity.
This is therefore a bug.


2012-12-02 14:10

administrator   ~0002606


2012-12-20 18:59

administrator   ~0002688

I degrade that to a feature request, since it include a major rewrite to the
python interface.

On how that interface should look like we need more information/ideas.


2012-12-29 19:12

developer   ~0002766

it should call OCC like in buildFromPoles. But the mults ans knots vexotrs should be given as pyhton iterables.


2013-10-04 16:14

developer   ~0003714

Last edited: 2013-10-06 06:31

for example (Poles, Weights, Knots, Mults, Degree, periodic) and (Poles, Knots, Mults, Degree, periodic)

static PyObject *
keywdarg_parrot(PyObject *self, PyObject *args, PyObject *keywds)
    static char *kwlist[] = {"poles", "knots", "mults", "periodic", "weights", NULL};
    PyObject* periodic = Py_False;
    PyObject* poles;
    PyObject* knots;
    PyObject* mults;
    PyObject* weights;

    if (!PyArg_ParseTupleAndKeywords(args, keywds, "O!|O!O!O!O!", kwlist,
        &PyList_Type, &poles,
        &PyList_Type, &knots,
        &PyList_Type, &mults,
        &PyBool_Type, &periodic,
        &PyList_Type, &weights ))
        return NULL;


2013-10-23 13:30

administrator   ~0003791

Why do you try to use pointers of TColStd_Array* And the method name buildFromEverything sounds a bit strange. Here we should find a better name. Does the code already work as expected?


2013-10-23 13:45

developer   ~0003792

I Agree about the name (it's just a placeholder by know)
The interpolation of knots (spacing) is not yet implemented. And i didn't do any testing yet.
I used pointers because i didn't know a better way to get the TColStd_Array* Objects out of the scope of my if clauses.


2013-10-24 05:59

administrator   ~0003793

Use smart pointer aka handles:
Handle_TColStd_Array1OfReal occweights;
if (...)
   occweights = new TColStd_Array1OfReal(...);
   occweights = new TColStd_Array1OfReal(...);

The problem with using plain pointers is that it's very difficult to release the memory in every situation. Especially, if OCC raises an exception (which often happens unexpected) you have a memory leak (in case you don't free the memory in the catch block). Thus, using handles always produces exception-safe code because the memory is freed when the scope where the object lives is left.


2013-10-24 07:51

developer   ~0003795

Before i read your post i rearranged my if clauses. This way i can create the TColStd_Arrays on the stack in the scope of the try block, abandoning all pointers.
The basic functionality is now completed. Documentation and Error reporting should be improved. Currently the user can supply inconsistent data that should cause ConstructionError exception in OCC. However the messages of the exceptions vary. But at least I'm not crashing FreeCAD anymore;)

The Names "buildFromKeywords" and "detailedConstructor" came to my mind. But i don't like them either.


2013-10-24 13:27

administrator   ~0003799

What about buildFromPolesMultsKnots()?


2013-10-25 05:35

developer   ~0003804

i changed the name and squashed the changes.
git:// review-0000895-buildFromPolesMultsKnots


2013-10-25 15:09

developer   ~0003806

I think it's now ready. It compiles on windows and 64bit linux. I did most of the testing on linux.


2013-10-26 06:24

administrator   ~0003810

OK. Might it be possible to add an example to the docstring of this method? Maybe an example for periodic and non-periodic splines. The examples shouldn't be too complex but not too trivial either.

You can add the examples to this ticket.


2013-10-26 06:52

administrator   ~0003811

git show 3a0037f


2013-10-26 07:29

developer   ~0003812

That's hard.
If just poles are given it works like buildFromPoles
the next step would be to just change the weights. (In a wiki page I would say that this is the R in NURBS ;)


I don't have an idea when one wants to change the spacing in the knot vector (the NU) in NURBS.

it might be a good idea to name the requirements:
len(poles) = len (weights)
len(mults) = len (knots)
if periodc:
  mults[0] = mults [-1]
  sum(mults[1:]) = len(poles)
  sum(mults) - degree -1 = len(poles)
the degree defaults to 3
the weights to 1
the knot vector to [0..1]
the mults vector defaults to uniform (if periodic) or quasi-uniform (if non-periodic)
BSplineCurve works with only the poles given.
BSplineSurface needs at least poles and mults (in u and v)
for Surfaces the poles and weights are gives as sequences of sequences.
the outer dimension matches u, the inner matches v

(note not be included) i was to lazy to guess the mults for a surface as well.
this function is for experts. If someone has not thought about mults for a surface he would be better of with an approximation or interpolation.
IMHO there should rather be an example page in the wiki with pictures of the results.


2013-10-27 10:55

administrator   ~0003815

I have added a few simple examples.


2013-10-27 10:56

administrator   ~0003816

git show 5678247

Related Changesets

FreeCAD: master 3a0037ff

2013-10-23 12:27:21

Sebastian Hoogen

Committer: wmayer Details Diff
0000895: Part.BSplineCurve: allow to set degree and mutliplicites when calling constructor.

Adds the functions:
Affected Issues
mod - src/Mod/Part/App/BSplineCurvePy.xml Diff File
mod - src/Mod/Part/App/BSplineCurvePyImp.cpp Diff File
mod - src/Mod/Part/App/BSplineSurfacePy.xml Diff File
mod - src/Mod/Part/App/BSplineSurfacePyImp.cpp Diff File

FreeCAD: master 56782476

2013-10-27 09:56:05


Details Diff
0000895: Part.BSplineCurve: allow to set degree and mutliplicites when calling constructor. Affected Issues
mod - src/Mod/Part/App/BSplineCurvePy.xml Diff File
mod - src/Mod/Part/App/BSplineCurvePyImp.cpp Diff File

Issue History

Date Modified Username Field Change
2012-12-01 09:09 shoogen New Issue
2012-12-01 09:23 shoogen Note Added: 0002605
2012-12-01 09:25 shoogen Note Edited: 0002605
2012-12-01 13:30 yorik Severity feature => minor
2012-12-01 13:30 yorik Category Feature => Bug
2012-12-02 14:10 wmayer Note Added: 0002606
2012-12-20 18:59 Jriegel Note Added: 0002688
2012-12-20 18:59 Jriegel Status new => feedback
2012-12-20 18:59 Jriegel Category Bug => Feature
2012-12-29 19:12 shoogen Note Added: 0002766
2013-06-30 12:49 wmayer Status feedback => assigned
2013-06-30 12:49 wmayer Assigned To => wmayer
2013-10-04 16:14 shoogen Note Added: 0003714
2013-10-06 06:31 shoogen Note Edited: 0003714
2013-10-23 13:30 wmayer Note Added: 0003791
2013-10-23 13:45 shoogen Note Added: 0003792
2013-10-24 05:59 wmayer Note Added: 0003793
2013-10-24 07:51 shoogen Note Added: 0003795
2013-10-24 13:27 wmayer Note Added: 0003799
2013-10-25 05:35 shoogen Note Added: 0003804
2013-10-25 15:09 shoogen Note Added: 0003806
2013-10-26 06:24 wmayer Note Added: 0003810
2013-10-26 06:52 wmayer Note Added: 0003811
2013-10-26 07:29 shoogen Note Added: 0003812
2013-10-27 10:55 wmayer Note Added: 0003815
2013-10-27 10:56 wmayer Note Added: 0003816
2013-10-27 10:56 wmayer Status assigned => closed
2013-10-27 10:56 wmayer Resolution open => fixed
2013-10-27 10:56 wmayer Fixed in Version => 0.14
2013-11-04 22:54 yorik Changeset attached => FreeCAD Master master 56782476
2014-08-03 08:00 shoogen Relationship added related to 0000337
2014-08-03 08:01 shoogen Tag Attached: NURBS
2017-03-27 08:28 Kunda1 Changeset attached => FreeCAD master 3a0037ff