Here's a step-by-step guide to help users understand the different ways of converting ellipses to polylines in AutoCAD, focusing on the PELLIPSE system variable.
Understanding the PELLIPSE System Variable
The PELLIPSE system variable in AutoCAD controls whether new ellipses are created as true ellipse objects or as polylines.
PELLIPSE = 0 (Default): Creates true ellipse objects. These cannot be directly joined into a polyline.
PELLIPSE = 1: Creates polylines that approximate an ellipse. These can be joined with other polylines.
Let's explore various methods:
Method 1: Creating a Polyline Ellipse Directly (Using PELLIPSE = 1)
This is the most straightforward method if you know you'll need a polyline ellipse from the start.
Set PELLIPSE:
Type PELLIPSE at the command prompt and press Enter.
Type 1 and press Enter.
Draw the Ellipse:
Type ELLIPSE at the command prompt and press Enter, or click the Ellipse tool in the Draw panel.
Specify the axis endpoints and distance to the other axis as prompted.
Verify:
Select the newly created ellipse. In the Properties palette (Ctrl+1), it will show "Polyline" as its object type.
Method 2: Converting an Existing Ellipse to a Polyline Using PEDIT (with PELLIPSE = 1)
This method is useful when you have an existing true ellipse object that you need to convert.
Ensure PELLIPSE = 1:
Type PELLIPSE at the command prompt and press Enter.
Type 1 and press Enter. (This setting affects how PEDIT handles the conversion.)
Start PEDIT:
Type PEDIT at the command prompt and press Enter, or click the Edit Polyline tool.
Select the Ellipse:
Select the ellipse you wish to convert.
Confirm Conversion:
AutoCAD will prompt: "Object selected is not a polyline. Do you want to turn it into one? [Yes/No] :". Press Enter to accept 'Yes'.
Exit PEDIT:
Press Enter to exit the PEDIT command (you don't need to perform any further polyline edits unless desired).
Verify:
Select the converted object. In the Properties palette, it will now show "Polyline".
Method 3: Using OFFSET to Create a Polyline Ellipse (with PELLIPSE = 1)
The OFFSET command, when applied to a true ellipse, can create a polyline ellipse if PELLIPSE is set to 1.
Ensure PELLIPSE = 1:
Type PELLIPSE at the command prompt and press Enter.
Type 1 and press Enter.
Start OFFSET:
Type OFFSET at the command prompt and press Enter, or click the Offset tool.
Specify Offset Distance:
Enter the desired offset distance (e.g., 10) and press Enter.
Select Ellipse:
Select the true ellipse object you want to offset.
Specify Side to Offset:
Click on the side of the ellipse where you want the offset to appear.
Verify:
Select the newly created offset object. In the Properties palette, it will show "Polyline".
Method 4: Converting with EXPLODE and PEDIT (less direct, but works)
This method involves exploding the ellipse into arcs and then joining them back into a polyline. This approach isn't directly controlled by PELLIPSE.
Select the Ellipse:
Select the true ellipse object you want to convert.
Explode the Ellipse:
Type EXPLODE at the command prompt and press Enter, or click the Explode tool.
The ellipse will break into multiple arc segments.
Start PEDIT:
Type PEDIT at the command prompt and press Enter.
Select an Arc Segment:
Select one of the arc segments that were created by exploding the ellipse.
Confirm Conversion:
AutoCAD will prompt: "Object selected is not a polyline. Do you want to turn it into one? [Yes/No] :". Press Enter to accept 'Yes'.
Join the Segments:
At the PEDIT prompt, type J (for Join) and press Enter.
Select all the remaining arc segments that formed the exploded ellipse. Press Enter.
Exit PEDIT:
Press Enter to exit the PEDIT command.
Verify:
Select the joined object. In the Properties palette, it will now show "Polyline".
Method 5: Using FLATTEN (Express Tools)
If you have Express Tools installed, the FLATTEN command can convert 3D objects (including some 2D objects with Z-values) to 2D representations, and it can also convert ellipses to polylines.
Ensure Express Tools are Loaded:
You'll find Express Tools under the "Express" tab in the AutoCAD ribbon.
Select the Ellipse:
Select the true ellipse object you want to convert.
Run FLATTEN:
Type FLATTEN at the command prompt and press Enter.
Remove Hidden Lines (Optional):
The command will ask if you want to remove hidden lines. For a simple 2D ellipse, N (No) is usually appropriate. Press Enter.
Verify:
Select the converted object. In the Properties palette, it will now show "Polyline".
By understanding and utilizing these methods, users can effectively convert ellipses into joinable polyline entities in AutoCAD, adapting to various scenarios and existing drawing conditions.