I think the title says it all.
Maybe I'm doing something wrong?

Hi niko - curves will only cap if the curves are closed and planar.

If you have projected your curves on to a curved surface, then you do not have planar curves.

What you can do though is to trim the surface by the curves, and then instead of extruding the curves, extrude the trimmed surface fragment instead.

When you extrude a face rather than a curve, it can be capped because MoI can copy the face to the end to make the cap.

If you just have some arbitrary non-planar curve MoI does not know how to create a surface to fill it in, that's why non-planar curves don't get an automatic cap on them.

Let me know if you need more details.

- Michael

Hi niko, also one other note - Trim actually has a projection method built into it already so it is not necessary to do the projection as an extra step.

So for example you have this surface and this curve:



Select the surface, run Trim, and then select the curve as the cutting object. Then right-click or press Done to keep all the cut up pieces. That will leave you with this result:



Select that small face, and then run Extrude:



- Michael

Hi Michael,

I thought of something when looking at this post, this only works for a single face, I just tried the same as your example but a joined surface with a seam in the center and I thought it would of been simple enough for MoI to work out, Oh well, it doesn't really matter I was just curious to see what it would do.

Cheers

Hi Danny, yeah currently extrude for surfaces is limited to only work on a single unjoined surface.

I do want to update it in the future to work with a joined surface as well, but currently you have to separate such things into individual surfaces first, and then extrude them. You can do a batch select of them instead of extruding them one at a time though.

The worry I had about extruding a joined surface automatically was that you could pretty easily create some messed up shapes if you did something like selected a box and then tried to extrude the whole box in one single direction. That would create something with degenerate flattened sides.

That's the part that is kind of harder to work out - trying to automatically figure out which kinds of joined surfaces would be ok to extrude and which would not. Maybe I will just not worry about that, but that was the issue.

- Michael

No big deal Michael, I'm not worried about it either :)

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Thanx Michael for the explanation
Your method should suffice