Hi Burr - believe it or not that is all working as intended... :)

When you do the "delete naked edges" step, that performs what is called an "untrim" operation, which will remove the trimming curves and recover the underlying surface.

Basically, surfaces in MoI are structured with a possibly larger underlying sheet which can then have trim curve information on top of it that marks which areas of the surface are cut away. There is some more description and illustration of this on this FAQ page entry.

When you delete those edges you are then exposing that underlying surface. When planar curves are turned into a trimmed surface, the plane tends to have a bit larger margin around the curves, and that is the plane that you are seeing there. You can also see the control points for the plane by picking those text surfaces and using Edit/Show pts, that may help to explain where those planes come from. I mean when you see the points you will be able to see that there are some planes there that are part of the definition of those trimmed surfaces.


Normally in a situation where you have created faces there you would select the whole faces to extrude rather than their edges. With the new beta that will automatically consume the face for you so you won't have any delete step.

Or if you did want to have a delete step then you would want to create the text as curve objects instead of as planar faces.

Or if you did want to extrude edges then you would not try to delete the edges, since they are not independent objects to be removed, they are a sub-object portion of another larger structure.

It's your step of deleting the edge curves sub-objects of the faces that produces the untrim effect.


Then the cube at the right appears due to the history updating mechanism - because that I letter shape has the same number of edge curves in it after it is untrimmed as before, the extrude history is able to find a match for the original edges used to build the extrusion, and then re-applies the extrusion which then makes that box. If you don't want that to happen you can select the extruded "I" and pick Edit / History / Disable update. That will turn off history updating for the extruded shape so it will no longer attempt to re-extrude it when the original input is edited.

By default history updating is enabled for the results of extrude so you can do things like extrude a curve, then turn on control points for the curve to edit it and have the extrusion update along with the edits to the curve.


Does that make sense?

- Michael