Radial dimension: Extension arc, how is it controlled?

Roy Klein Gebbinck

If you measure an arc with a radial dimension, and position the dimension so that the arrow in not on the arc, an extension arc (belonging to the dimension) will appear. Does anybody know which settings or variables control this extension arc? You can control the color of the extension arc through the extension line color. And if you (programmatically) remove the xdata of the dimension the extension arc will disappear. But why does it appear in the first place? How is it controlled or is this (fixed) default behavior?

Knut Hohenberg

Hi Roy,
my understanding is definitely poorer than yours, but here are my two cents anyway:

In a sane implementation, I think the extension arc should be controlled by settings for the extension lines, but apparently this is only partly so:
- DIMEXE seems to work as expected
- DIMEXO seems to have an effect when the dimension is created, or if the value of DIMEXO is changed via DIMOVERRIDE, but if the dimensioned arc is altered, the gap between arc and extension changes unpredictably
- DIMSE1/DIMSE2 does not have an effect (I would have expected DIMSE1 to suppress the arc display)

BricsCAD hides these vars in the properties bar, probably in order to shield the user from insane complexity, but I don't think it's a good idea.

Things become more strange when you set DIMASSOC to 1 and create a radial dimension. In my understanding, the dimension object should then not know anything about the dimensioned entity, but should be controlled by defpoints only - but no defpoint/grip appears for the clicked point, and the dimension still seems to carry information derived from the original arc.

Looks buggy to me, but I don't know if Bricsys or Autodesk are to blame, and I guess this hits so few users that neither one will be willing to do some housekeeping here... but do you want to file an SR anyway?

Jason Bourhill

Hi Roy,

Looks like DIMSE1 is supposed to control the display of the arc extension. See comparison made in BricsCAD and another well know .dwg CAD app. So looks like BricsCAD is ignoring this setting, and yes you would have to raise a support request.

Fixing would raise another issue, as DIMSE1 & DIMSE2 are used by other dimension types e.g. _DIMLINEAR. You would have to use an override on all your radial dims. In ACAD you can use dimstyle families to define different settings for dimension types while keeping grouped under the same main style. Have previously raised a support request on this.

regards,

Jason Bourhill

CAD Concepts

DimRadiusBCAD.png

DimRadiusACAD.png

Roy Klein Gebbinck

@ Knut:
Thank you for pointing out the DIMEXE and DIMEXO variables and the DIMOVERRIDE command. When I started this topic I hadn't yet experimented with these variables. And the command was unknown to me. I have also encountered the 'gap' problem you report.

@ Jason:
Thank you for the visual confirmation.

I'll send in an SR regarding this.