Complex extrusion

I am trying to extrude up a masterplan of paths slightly so that they are all one surface (which I can then render). However I am having a problem with trying to get them to do this. It’s easier to see the attached screenshots then explain, but basically I have closed every gap I can find and joined all the parts together. But when extruding I still get this same message and then the following result:

however I want these to be connected so that the extruded surface is the (badly photoshoped) surface below:

Appreciate any help



If you can post the Rhino file, it will be easier to find the problem.


Hi Sam, here you go

westewrn harb for lumion2222.3dm (1.3 MB)

Did you try to project to c-plane to make sure they were all planar – and then connected? You can always re-project them back to another deformed surface later.

You’ve got a fair number of problem areas. One way to find them is to SelClosedCrv and hide. What’s left is what you need to work on. For each of the remaining curves, you can find the problem area by using CrvStart or CrvEnd which will drop a point and the start or end of the curve. If you zoom in on that point, you will see where your curve is failing to come together.

Below is what I found:

If you don’t need the clean curve geometry for other uses I would suggest to make2D the shape in the top viewport and work with that geometry instead for the extrusion.

Hi Cormac,

May I suggest to lower your tolerance for this file?
The area is large (300meter across) and with a tolerance of 0.001 mm, calculations like extruding and the below suggested CurveBoolean will take longer than needed (if at all)

As for your issue, I suggest to use the CurveBoolean Command.
First up the file absolute tolerance to 1mm (if you can afford that).
Next close the gap in the highlited curve:

Than perform a curveboolean on the complete set:
You need to decide what to to with the area indicated with the red line:

The result can be extruded:

If needed you can set the tolerance back.


Thanks for all the advice guys some great tips here!

@Willem Not sure I get the curveboolean command, I followed your steps but it ended up just crashing rhino


That should not happen…Maybe you can report in more detail what caused the crash as this might be a bug or malfuntion.


Hi, it seems it was my fault somehow the units reset back to 0.001 after I changed them so obviously crashed the program when I selected all the geometry at that tolerance!

Just wondering as well, whats the best way to delete all the points after they have shown where the gaps are? I did this by changing the curves to a different colour and then selcolor-ing the black dots, but I’m guessing there is a more logical way?

Many thanks!

Hi Cormac - SelPt will select point objects ( as well as control points).