Weird Surface

In this file

Problem41.3dm (349.5 KB)

the surface looks like

in wireframe but looks like

when rendered.

What is happending?

Display mesh setting are too coarse. Go to DocumentProperties menu and in Mesh change to “Smooth and slower” instead of “Jagged and faster”. (Based on Rhino for Windows).

Hi Jim - see if RebuildEdges gets you anywhere with this object.


Thanks, both worked.

After changing the display resolution (Mesh > Render Mesh Properties > Smoother & slower) the result was as desired.

However, I then attempted to Trim the surface (DupBorder, Trim) to get rid of the remaining surface where the tight curve is. (below)

The result was this (below)

RebuildEdges then gave this result (below)

I also tried ShrinkTrimmedSrf with no effect, with the response being that the surface is already shrunk.

Suggestions to resolve this?

(@bigjimslade: Given the high number of U’s and V’s, I suspect you might get more desirable, and more easily modified results if you had a much lower number of each. If you like this shape, you could extract a few isocurves (Curve > Curve from Objects > Extract Isocurves) at several key points (such as kinks) and recreate the surface from network curves), or manually creating surfaces of desired shape that can be joined.)


Hi Jim, Dave - DupBorder, Untrim, then Trim again with the border curve - that seems to clean it up here, even at the default mesh settings. I’ll see if I can find out why the current trims are a problem for the mesher.

Hmm - there seem to be multiple trim curves piled up in some places… still poking…

@bigjimslade - is this made in Rhino? If not where did it come from, and can you send me via private message, the file that was imported to Rhino? Thanks.


I made the whole thing in rhino. I imported a table of offsets from a spreadsheet, Then I faired waterlines; generated new frames; faired the frames; generated new waterlines. Repeat a half dozen iterations.

I posted the whole result to another question on how to better skin this.

Note that I do not need all the frames or waterlines. I just need to get the correct shape.

The result of patch is almost perfect, except that the stern the match is very poor, creating visible ripples.