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30 minutes ago, I launched blender for the first time. I'm rather overwhelmed by the options, so I dare to ask this novice question.

I'd like to export the control points of a NURBS into a text file. If possible I'd prefer homogeneous coordinates.

  1. For the start, I have created a path and modified it to look like a quadratic Bezier curve.
  2. I've exported to different formats, but didn't find NURBS data in them (e.g. dae file contains lamp and camera, obj contains coordinates of the curve).

How can I obtain the control points and knot vector?

I found this, but I'm not sure how to use it and if it could be helpful.

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  • $\begingroup$ Its not clear for this question if you are asking about OBJ file format support or how to access the API to write this yourself. $\endgroup$
    – ideasman42
    Commented Sep 26, 2014 at 15:09
  • $\begingroup$ Sorry, ideasman, indeed I don't care about .obj. All I want is a way to extract knots & control points. I would love a general solution involving api calls, since .obj provides only univariate NURBS data $\endgroup$
    – Sebastian
    Commented Sep 26, 2014 at 17:03

1 Answer 1

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OBJ Format supports nurbs, but Blender writes them as edges by default (since many applications don't support them).

File -> Export -> Wavefront OBJ

Then in the options, enable Write Nurbs. This currently only supports Nurbs splines (not surfaces).


If for some reason you need to access different kinds of curve data, writing nurbs to a text file from Python isn't all that complicated.

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  • $\begingroup$ ohh, I missed that checkbox! looks excellent. $\endgroup$
    – Sebastian
    Commented Sep 26, 2014 at 10:45
  • $\begingroup$ On a side note: This seems to work only on univariate NURBS (i.e. curves and paths, but unfortunately not surfaces) $\endgroup$
    – Sebastian
    Commented Sep 26, 2014 at 14:27

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