I have to create segments like the one in the picture:

enter image description here

I need to draw a segment where there is a straight line and other parts of segments with arcs of different angles.

The part of the segment that curves must be only created by 3 points, a starting a center, and an ending point.

Creating different arcs can be a solution but the contact between two arcs create a step that I don't want. Probably a cube spline can be the solution but I cannot find a working plugin for QGIS 3.4.

I installed the QAD tool, which is the CAD plugin but even there I cannot find the solution.

I just tested in ArcGIS the tool 'Bezier Curve Segment' and it does what I am searching for. Does this functionality exist in QGIS?

  • 1
    Do you want the feature to be displayed this way, or does the geometry actually have to be like this?
    – Erik
    Jun 9 '20 at 18:45
  • I want a tool that allows to create a segment as the one in the picture.
    – high_point
    Jun 9 '20 at 20:35
  • 1
    This doesn't answer my question.
    – Erik
    Jun 10 '20 at 5:55

In QGIS 3.10, I can suggest paying attention to two cases.

  1. A Native QGIS's toolbar 'Shape Digitizing Toolbar' where you can 'Add Circular String', see image below.


  1. A QGIS’s Plugin 'Bezier Editing'.


'Bezier Editing' toolbar looks as following


The result of applying the 'Bezier Editing' Plugin might be this



  • 1
    'Bazier Editing' plugin creates the geometry that I am looking for. But, unfortunately, as also you can see the created line is not smooth, but looks like several segments connected to each other. Probably does not exist a better tool for QGIS.
    – high_point
    Jun 11 '20 at 6:50

With QAD you can create a polyline (PLINE command) by marking some points that it goes through.

Once the polyline is created you can give it curvature from the command PEDIT, select the polyline, and use the Fit option to curve it.

The polyline is a little straight segments multiline. I don't know the standard about curved multilines yet, but you can start with this approach.

Another option is to decompose the curve analytically to know the parameters of each arc that makes it up and to draw each arc separately, but the task may be impossible if you do not know the analytical definition of the curve.

  • This solution works only if the segment is curved. In some cases, I got a straight line that becomes curved. And also if is curve in the entire length, once the command Fit is applied the curvature is not smooth as the one in the picture above but still, there are some many curves (as many as the number of the points)
    – high_point
    Jun 10 '20 at 6:46
  • You can draw a straight polyline and fit another and then join them. But yes, it works with the multiline standard not with the curved multiline one. Jun 10 '20 at 13:26

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