I created a default star and applied the default motion extension to it. However, the resulting image is missing one edge (see picture). What am I doing wrong?

nice post.

Hi

You are doing nothing wrong. The motion effect is an extension to Inkscape.
The author of the extension probably never tested it with a star or with any shapes with more than 'X' nodes?
There are some other faults as well as new faces does not cover 'hidden lines' as seen in the bottom of 'your' star.

If you have a little python programming knowledge and know a little about the SVG specification http://www.w3.org/TR/SVG11/ feel free to 'fix' the extension.
The extension code can be found in Inkscape_install_dir\share\extensions\ the file is motion.py.
Fixing the extensions can be difficult as most authors did not leave any comments in the code (bad practice) to show how the code is working.

For your star having snapping set to node endpoints and intersections drawing the 'Motion effect' can be done in about 20 seconds manually.

RGDS
Ragnar

Thank you for your answer. The star is just a testcase. I have a complex shape with many verteces and Bezier curves, which I want to move. I'll see if I can make some sense of the Python code.

Is there by any chance another tool suitable for the task? I tried Extrude, but it can't handle Bezier curves.

Here is how to overcome the problem:

Convert the star tool to path (Ctrl+Shift+C),
select the starting node of the path with the node tool and split it to two (Fourth icon from the left).

That way the extension won't miss a segment from the selected path.

I seem to be lucky after all. With my picture, the extension only omits two straight segments, which can easily be fixed manually.