Native AutoCAD dimensioning tools are excellent for standard geometry, but they reach their limits when you need a single, continuous dimension covering a path made of different object types—specifically a mix of arcs and polylines.
This situation is common in mechanical layouts, piping runs, architectural contours, and fabricated plate profiles where the geometry transitions between straight segments and curves.
The Problem: Segmented Dimensioning
Standard dimension commands such as DIMLINEAR, DIMCONTINUE, or DIMALIGNED treat arcs and polylines as separate entities.
If a polyline transitions into an arc, AutoCAD forces you to create two independent dimensions. The result:
- Multiple dimension strings for a single logical run
- Reduced drawing clarity
- Higher risk of misinterpretation during fabrication or site work
From a drafting standards perspective, this is inefficient and visually cluttered.
Understanding Why AutoCAD Behaves This Way
AutoCAD dimensions are object-based, not path-based.
- A line has a linear length.
- An arc has an arc length.
- A polyline can contain multiple segments but is still treated as a single object.
Unless geometry is unified into one object, AutoCAD will not compute a cumulative length automatically for dimension display.
Primary Solution: DimCurve Utility (LISP-Based)
There is no native dimension style that aggregates mixed geometry into a single dimension label. The most efficient method is a specialized LISP routine.
One widely recommended solution is the DimCurve utility.
What DimCurve Does
DimCurve allows you to:
- Select multiple connected objects
- Combine lines, arcs, and polylines
- Generate a single dimension reflecting the true cumulative path length
It calculates the actual length along the curve, not the straight-line distance between endpoints.
Implementation Steps
- Download the Utility Obtain the “DimCurve” add-on from the Autodesk App Store or a reputable CAD community repository.
- Load the LISP File Use the
APPLOADcommand in AutoCAD. - Run the Command Execute the command (typically
DIMCURVE). - Select the Path Segments Select connected objects in order.
- Place the Dimension The routine generates a cumulative length dimension.
Associativity Considerations
Most LISP-generated dimensions are:
- Static
- Or semi-associative
If geometry is modified significantly, you must regenerate the dimension to ensure accuracy.
For production drawings that change frequently, this is an important workflow consideration.
Native Method 1: Join into a Single Polyline
If third-party utilities are not an option, the most robust native method is to convert all segments into a single polyline.
Step-by-Step Procedure
- Use
PEDIT - Select one object
- Choose Join
- Select all connected segments
- Confirm they merge into one polyline
If successful, you now have one unified object.
How to Retrieve Total Length
You have two options:
- Use
LISTto read the total length manually - Use a Field to create a dynamic length label
Native Method 2: Dynamic MTEXT with Fields (Fully Associative)
This approach avoids LISP and maintains associativity.
Procedure
- Ensure the geometry is a single joined polyline
- Insert
MTEXT - Right-click → Insert Field
- Category: Object
- Select the polyline
- Choose property: Length
The MTEXT will now display the polyline length.
Advantages
- Fully associative
- Updates automatically when geometry changes
- Compatible with AutoCAD LT
Limitation
This is a text label, not a graphical dimension line. If your drawing standard requires a dimension line with arrows, this method does not replicate that visually.
Native Command Clarifications
Why DIMARC Does Not Solve This
DIMARC measures only the arc length of a single arc object. It cannot aggregate multiple segments or mixed geometry.
Why QDIM Is Not Suitable
QDIM creates multiple dimensions at once. It does not compute cumulative length across different object types.
Advanced Alternatives
Depending on your workflow and software configuration, consider the following:
Express Tools
Some Express Tools provide extended dimension utilities, but none aggregate mixed geometry automatically.
Data Extraction
You can use Data Extraction to report lengths of multiple objects and sum them in a table. This is useful for reporting but not for graphical dimensioning.
AutoCAD Civil 3D
In Civil 3D, Alignments inherently manage cumulative stationing along complex paths. For infrastructure workflows, this may be a better long-term solution.
Common Pitfalls
1. Objects Not Truly Connected
If segments are not perfectly joined:
- Gaps smaller than visible tolerance may exist
JOINmay fail- Length values may exclude disconnected pieces
Use OVERKILL and adjust join tolerances when necessary.
2. Non-Coplanar Geometry
If objects are not in the same plane:
- Join operations may fail
- Length calculations may behave unexpectedly
Check UCS and elevation values.
3. Polyline Width
Polylines with width can cause confusion in fabrication drawings. Length is calculated along the centerline, not outer edges.
4. Splines Converted to Polylines
Spline conversions introduce segmentation and approximation. Length accuracy depends on conversion settings.
AutoCAD LT Considerations
AutoCAD LT does not support LISP routines.
Best available method:
- Join geometry into a single polyline
- Use an MTEXT Field referencing the polyline length
This provides dynamic updating without external tools.
FAQ
Can I use the standard JOIN command to solve this?
Yes. If arcs and lines are contiguous, use PEDIT or JOIN to create a single polyline. After joining, you can retrieve the total length via LIST or insert a Field referencing the Length property.
Does QDIM work for continuous paths of different object types?
No. QDIM creates multiple individual dimensions. It does not aggregate arc and line lengths into a single value.
What happens to a DimCurve dimension if I modify the geometry?
Most implementations are static. If geometry changes, you must regenerate the dimension.
Is there a fully associative graphical dimension solution without LISP?
Not natively. AutoCAD does not provide a built-in dimension style that aggregates multiple object lengths into one associative dimension line.
Why does AutoCAD allow arc length dimensions but not cumulative mixed paths?
Because dimensions are tied to individual object definitions. AutoCAD does not treat separate objects as a single measurable path unless they are joined.
Is the Field method reliable for production drawings?
Yes, provided the geometry remains a single polyline. If the polyline is exploded or partially modified, the Field reference may break.
This workflow decision comes down to project standards:
- If you need a graphical dimension line: use a LISP utility.
- If you need dynamic length tracking: use a Field on a joined polyline.
- If you require reporting and quantities: use Data Extraction.
Each method has a valid use case.
