You can create dimensions for the curvilinear length of a curve. However, you should be familiar with some concepts that are described in this topic before you begin creating curvilinear length dimensions.
Important:
the curvilinear
length dimension is not created in true length mode: it means that
the curvilinear dimension measures the length of the projected curve
and not the length of the 3D curve.
Curvilinear length dimensions can be created using the Dimensions
and Length/Distance Dimensions commands; they cannot
be created using the Stacked Dimensions and Cumulated
Dimensions commands.
You can create curvilinear length dimensions for all types of curves:
splines, circles, arcs of circle, conics, etc. Note that in the case
of circles and arcs of circle, they will be called circular length
dimensions.
You can also create curvilinear length dimension for straight lines,
but only if theses lines are generated from 3D. This is useful if you
change these straight lines into curves in 3D and then update the view.
The linear representation mode for the dimension line is:
forbidden in the case of closed curves.
the only authorized representation mode for True Length dimensions.
the curvilinear length dimension is not created in true
length mode: that's means that the curvilinear dimension
measures the length of the projected curve (and not the length of
the 3D curve)
Important:
You cannot change the dimension line representation mode or orientation
after the dimension has been created.
In the case of the parallel and offset representation modes, the
dimension value cannot be moved out of the curve limits, except for
circles and arcs of circle. As a result, you cannot specify the dimension
value position (Inside, Outside, Auto).
In some cases, depending on the curve and on the offset value, the
offset representation mode cannot be computed:
In certain cases, when switching from another representation
mode to the offset mode, the dimension will be previewed as being
not-up-to-date (i.e. using the color configured in Tools >
Options > Mechanical > Drafting > Dimension tab,
Analysis Display Mode): try to move the cursor closer
to the dimension.
In other cases, you will not be able to position the dimension
further than a certain limit. The examples below show the limits
for positioning a curvilinear length dimension in offset mode for
a spline.
In the case of curvilinear length dimensions in offset mode, it
is recommended to activate the Constant offset between dimension
line and geometry setting in Tools > Options > Mechanical
> Drafting > Dimension tab. This will ensure that the dimension
remains associative if the geometry is moved.
When dimensioning a 3D curve that is not planar, the extension line
of the curve will extend to the projection of the endpoints of the curve
in the view plane of the dimension. As a result, the dimension may seem
to point nowhere.
Curvilinear dimensions cannot be measured along a direction.
Curvilinear dimensions cannot be driving dimensions.