Bug? Can't offset particular polyline.

[R Muller]

I am working with polylines in AC21, using "offset all edges" from the pet palette while holding down command and option keys, and I can offset the line as many times as I need to. Very useful for drawing sets of parallel contour lines on a site plan, so I can later turn them into a mesh.

However, sometimes I select a polyline that can't be offset. The offset option doesn't appear in the pet palette and can't even be chosen from the menu. That particular polyline just can't be offset, either in teamwork or in a stand-alone model.

After some head scratching, I finally realized that the problem lines were all single segment polylines. If I add a new segment or insert a new node, so the polyline has at least two segments, then the line can be offset. At least now I have a work-around. I note that splines don't have this problem.

Is this a bug? Is it intended behavior? Does this work the same way for everyone? I am using AC21 on a Mac.

[Bruce]

I don’t think it’s a bug from what you describe. You can unify these separate lines into a single one - that will solve the problem.

[R Muller]

Bruce, thanks for your response. The reason the lines aren't unified is because I just cut them.

My work process to modify the contours to insert a road is as follows:
1. Cut the unified polyline where the contour will cross the road.
2. Offset half of the cut line to the other side of the road, using "offset" to keep the shape concentric.
3. Draw the contour across the road to join the original line and the offset line.
4. Re-unify the lines.

This works fine except where I am working close to the edge of the site, so there is only one segment remaining after I cut the contour in step one. The work-around requires an additional step 1a after cutting the line: Modify the contour to be offset by adding an additional point so it will have 2 segments rather than only one.

The reason I think this may be a bug is because if I use splines instead of polylines the offset of a single segment spline works as it should.

[Bruce]

Fair enough. - that's for GS to answer.

[Daniel Kovacs]

Hello guys,

This is a bug. It worked fine until ARCHICAD 18, since then it is faulty. Thanks for pointing this out.

Regards,