Refit trim - accuracy issues

I’m having accuracy issues with Refit trim on the below surface. One side re-trimmed ok. the other just won’t retim nicely. ICEM Surf did it with no problems though. File below…

Refit_trim_issues.3dm (79.0 KB)

Hi Rob, thanks for this example.
RH-70065 RefitTrim - example -could be closer


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RH-70065 is fixed in the latest WIP

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Just had a go with the new refit trim and think I’ve stumbled upon a bug with the new ‘degree altering’ function (by the way thank you for that!).

It seems to be creating a small sliver of a trimmed surface as the result of the refit trim. Only happens when you tinker with the degree value (from my brief testing).

See the pics below for visual explanation and Rhino file also attached…

…and the Rhino file…
RefitTrimIssue.3dm (163.8 KB)

I’ve also got a case where the refit trim fails. File and snap shot below…

RefitTrimIssue2.3dm (65.6 KB)

From my brief testing, this happens when you try to increase the degree from an original degree 1 surface. Is this also the case in your tests?

Correct, I’m increasing it from degree 3 until I get an ‘acceptable’ deviation.

I haven’t tried starting with a higher degree and then dropping it though.

Thanks, I’ll do some more testing and report back. Lowering the degree is not an option btw.

Thanks for reporting, logged as RH-71764 RefitTrim fails when increasing the degree

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As for your other file, the edge you try to RetrimFit, contains 5 separate edges, of which two are very short, I cannot merge the edges. It needs to be a single edge.
If I DupEdge those edges and rebuild the resulting curve, extrude that and make a clean trim, so that I get one edge, RetrimFit works as expected.

Ok, good to know. Thanks.

But do let us know if it should be.

Oh, ok! I think that was trimmed over two surfaces - one large one, and then partially over an adjoining surface (but both curvature matched).

I was hoping the refit could average out over this curve rather than fail (even if the best average is way out of ‘tolerance’, so long as it’s reported to me in the command line).

Will keep that in mind!

I guess it’d be great for flexibility but the general way I’d be using it is - I start with lower degree surfaces and then only increase if I need to. So going the other way isn’t really in my personal ‘workflow’.

If I do need to drop a degree for any reason I can’t see a problem with doing a ChangeDegree command before a RefitTrim.

Thanks Gijs.

I will ask the dev what’s possible, thanks

@mcvltd apparently this is already on the list as RH-64006 Refittrim: Merge split edges

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Possible bug with Refit trim -

With this particular surface, refit trim increases the degree on the wrong side (along V instead of U).

RefitTrimIssue3.3dm (58.4 KB)

thanks Rob,
RH-72103 RefitTrim increases degree of surface in the wrong direction

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