Boundary of 2d Curve object


I would like to know if there is a command in Rhino 7 to extract the boundary of a 2D object? (made from a 3D model - Make2D)

For example, I would like to get the boundary of this profile view of a Engine:

Thanks for any suggestions in advance.


CurveBoolean command with commandline option CombineRegion=Yes and then click AllRegions in the commandline

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Thanks for the suggestion.
The command has been running for about 10min now. So I don’t think that’s a solutions for what I am looking to do.

It is a solution for what you are looking to do, even though it might not be so effective. Have you tried Silhouette on your 3D model? Hard to give any more advice without a file.

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CurveBoolean becomes slow really quickly when using many curves. So the long wait is to be expected. If you run Make2d there is a silhouette option but that oftentimes fails to generate a full outline. You can try _Silhouette as @siemen suggested or if the model has the outline flush with a plane, run a _Cutplane through the model, intersect it with the model and pick the outer curves.

I have tried the Silhouette command on the 3D but it gives me a messy result with inner curves.
Unfortunately Make2d with the silhouette option also gives me the messy result.

My goal is to create outer boundary of equipment parts, preferably without to many steps .

Another way could be Meshoutline first, then Curveboolean. The meshoutline should result in less complex curves for Curveboolean to process and get just the outline.


Some possible speedup options:

You could manually hide or deselect some of the inner curves you know are not part of the outlines.

Temporarily increase the document tolerance say from 0.001 to 0.1

Tweek for CurveBoolean :wink:
Draw closed boundary rectangle or circle

Then use CurveBoolean, then click inside your drawn boundary object.

Delete your drawn boundary object.

Thanks for all the input.

So far when I delete some of the inner curved it becomes a bit quicker to use the _CurveBoolean command.

But still no one click magic “_CreateCurveBoundary” command

Please, can You upload an example file ?

Block (9.9 MB)

I don’t think you need to draw this extra outside boundary curve. If you just click on the outside of all objects it automatically joins everything together. It does the same as clicking “AllRegions” in the commandline.

Hi Siemen,

I would like to have that outside boundary curve so that I can use it as a wipeout boundary in AutoCAD. Therefor I can place blocks over each other in a 2D space. Removing the need to trim fine details when Equipment overlap.

another workaround (no calculation delays) is to make a black and white display mode then save the view to image and convert it to vector with the Vectorize plugin

It might even be partially scripted



Hi Gijs,

This option could work, how do I set my display mode to Black & White?

I thought of isolating region, so no matter if CombineRegions true or false.
Unfortunately it was only wishful thinking.
Calculation time is a nightmare.
And on You opened step file then I see that !!!
this is why calculations are sooooo slow

Hi @eddi

I Presume that bad!

What do you usually make that? 0.1?
The file we recieved from supplier

We make that what industry branch specification is.
Woodworking, metalworking, electronics or architecture…

…spaceflight, nano-architecture :wink:

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