How to

How to convert 3d polyline to polyline in AutoCAD?

Brief Answer: To convert a 3D polyline to a 2D polyline in AutoCAD, use “Convert 3D To 2D Polylines” Command or the “FLATTEN” command to remove the Z-axis data.

Detailed Explanation and Solutions:

  1. Understanding the Issue:
    • A 3D polyline in AutoCAD includes elevation data (Z-axis), which might not be needed for certain 2D applications.
    • Converting to a 2D polyline simplifies the geometry by removing this elevation aspect.
  2. Using Convert 3D To 2D Polylines Command:
    • Locate the Command: Go to the Modify tab, then the Design panel, and find the “Convert 3D To 2D Polylines” tool.
    • Select the 3D Polyline: Click on the 3D polyline you want to convert.
    • Execute the Command: After selecting, press Enter.
    • Result: The new 2D polyline will be created, taking on the elevation of the start point of the 3D polyline.
  3. Using FLATTEN Command:
    • Select the 3D Polyline: Click on the 3D polyline you wish to convert.
    • Type FLATTEN: Enter FLATTEN in the command line and press Enter.
    • Confirm the Selection: When prompted, press Enter again to confirm the selection or select additional objects.
    • Apply FLATTEN: The 3D polyline will be converted to a 2D polyline, removing any elevation data.
  4. Manual Conversion (Alternative):
    • Redraw the Polyline: Use the PLINE command to manually trace over the 3D polyline.
    • Snap to Existing Points: Use object snaps to accurately trace the polyline’s vertices.
    • Complete the PLINE: Once finished, you will have a 2D version of the original 3D polyline.
  5. Using EXPLODE and PEDIT:
    • Explode the 3D Polyline: Type EXPLODE and select the 3D polyline. This breaks it into individual line segments.
    • Convert Line Segments to Polyline: Use PEDIT, select the line segments, choose “Yes” to convert them to polylines, and then select “Join” to combine them into a single 2D polyline.

Key Points:

  • Preserve Original: Consider working on a copy of the polyline in case you need to revert.
  • Check Elevation: After conversion, check to ensure all Z-axis values are set to zero.

By using these methods, you can effectively convert a 3D polyline to a 2D polyline in AutoCAD, suitable for applications where elevation data is not required.

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