Slicing Regions and Planar Closed Curves (splines, polylines, ellipses or circles)
In the course of looking for a simple way to slice Regions and Closed Planar Curves like polylines, splines, circles and ellipses just by using existing command functionality and without using custom “curve intersection programming” methods and tools, I found out that the command BOUNDARY does the trick by the vast majority of cases !!!
So I would like to share the findings with you and describe the underlying Rules and Procedure.
The most consistent way to approach the subject is to use always 3 elements :
1. Draw the regions and closed planar curves to be sliced (splines, polylines, ellipses or circles)
2. Draw an enclosing Curve (spline, polyline, ellipse or circle) for the regions and other curves to be sliced
3. Draw the slicing curves (lines, splines, polylines, ellipses, circles) extended to the boundary enclosing curve.
Then call the command BOUNDARY and click the “Pick Points Button”
At the command prompt don’t pick any point and select the command option <Select entities> S
“Pick a point to define a boundary or hatch area or [Select entities/Undo]: s “
Select all 3 elements mentioned above (1)(2)(3), curves and regions to be sliced, enclosing curve and the slicing curves respectively.
Then click Return and you come back to the dialog…
Just click OK !
If regions are created then you get the Prompt :
“Polyline boundary could not be derived. Create Region? [Yes/No] <Yes>:Y “
Type in Yes and then Return….
That’s it…the closed planar curves and\or regions are sliced !
The original curves are still there, but new closed curves or regions are created representing the sliced parts of the original objects !
There are some Rules that apply :
1
If the enclosing curve is a spline or ellipse and the enclosed objects are regions or polylines not containing ellipses, elliptic arcs or splines then the created sliced parts are regions (cyan).
2.
If the enclosing curve is a polyline and the enclosed objects are regions or polylines not containing ellipses, elliptic arcs or splines then the created sliced parts are polylines (green).
3.
If the enclosing curve and/or the enclosed curves/regions and/or the slicing curves contain or are ellipses and splines then the created sliced parts are regions (cyan).
It is very interesting that the described procedures apply also for regions with islands (holes) !
See slicing in the blue rectangle.
Some “collateral parts” (yellow) are sometimes created but can be ignored, the final slicing is correct by the vast majority of cases and mostly consistent.
You find attached a test DWG.
For those interested for more functionality of the boundary command, have a look at thread
Enjoy slicing !
Comments
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Thanks for sharing!
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