topic NurbSpline Creation Error in Revit API Forum

NurbSpline Creation Error

Anonymous — Tue, 26 May 2015 22:59:15 GMT

I'm working on a Revit plugin that in part accepts curves from Rhino that can be used to create a beam in Revit.
My code works well, when controlpoints of curve are greater than or equal to four. But with three control points arises a problem.
How can I draw three control points curve in Revit API?

List<XYZ> ctrPoints = new List<XYZ>();

ctrPoints.Add(new XYZ(Utils.mmToFeet(72500.017337), Utils.mmToFeet(-5072.522765), Utils.mmToFeet(0)));
ctrPoints.Add(new XYZ(Utils.mmToFeet(105082.371745), Utils.mmToFeet(-748.798009), tils.mmToFeet(0)));
ctrPoints.Add(new XYZ(Utils.mmToFeet(117899.12727), Utils.mmToFeet(-15572.997171), Utils.mmToFeet(0)));

List<double> weights = new List<double>();
weights.Add(1);
weights.Add(1);
weights.Add(1);

List<double> knots = new List<double>();
knots.Add(0);
knots.Add(0);
knots.Add(0);
knots.Add(52464.568605);
knots.Add(52464.568605);
knots.Add(52464.568605);

NurbSpline detailNurbSpline = NurbSpline.Create(ctrPoints, weights, knots, 3, false, true);

Re: NurbSpline Creation Error

jeremytammik — Wed, 27 May 2015 10:57:33 GMT

Dear Anarchyfree,

Congratulations on your interesting project!

I am glad to hear that it is working well.

Would you like to share some of it here? I am sure there would be a lot of interest in that.

To answer your question:

The exception thrown when this code is run explains that there must be at least degree + 1 control points.

Since the degree passed in is 3, this code violates that rule.

Revit’s version of creating splines is NurbSpline.Create(<<control points>>, <<weights>>).

It automatically sets the degree based on the number of points as described in this internal comment:

// Use degree 1 for two CPs, degree 2 for three CPs, and degree 3 for four or more CPs.

Best regards,

Jeremy

Re: NurbSpline Creation Error

Anonymous — Wed, 27 May 2015 22:10:09 GMT

Thank you for your answer!

I wanted to represent a curve of 3 Control points such arch. then an error message was generated. Please see the attached pictures.