Correcting a default on a surface, polysurface to mesh

Hi Everyone,

I am trying to convert a polysurface into a mesh for 3D printing, however by converting it into a mesh i noticed that there was some default on the surface. I tried to rebuild the surface but same problem again.
If it’s impossible to change it on the initial surface, is there a way at least to modify it on the mesh when converted?

Thanks in advance,


Look at the detailed mesh settings, try doing things that increase the number of polygons to try to make those go away.

Hi Jim,

I already tried different mesh settings, but the issue seems to come from the surface itself even before the conversion. I think it happened when i splited with the pattern.

Maybe ShrinkTrimmedSrf and/or DivideAlongCreases with SplitAtTangents=yes could help

I tried both, together and separatly, only the shrink trimmedsfr changed the a bit the surface but it just moved the defaults to other places.

I also try to create the surface in a different way and apply the pattern after, so initially the surface was created with patch, and then i tried with rail revolve. everything is fine until applying the pattern. with rail revolve the default are still there but instead of being orientated like on the picture, they are orrientated along the radius of the rail revolve.

What i don’t understand is that the surface analisysis before the pattern is perfectly fine, but after applying it it is very messy. the pattern is applied with the commend split, so i though it would just cut the surface, but it seems to modify it also.

It’s that meshing a polysurface with a ton of holes in it is tricky, the basic geometry is fine.

Increase the “minimum initial grid quads” setting, use the “maximum edge length” to try to stop such long skinny triangles from appearing. Running Reparameterize with the Automatic option on the object (you’ll have to window-select all the surfaces in it) may also help.

Hi @JimCarruthers what could be the use of the Reparametrize command? I read the help file but is too short to understand the function

When the “internal coordinate system”
, the values along the U and V, of surfaces is greatly different from their actual size, it can confuse the mesher. That mostly happens with objects that have been heavily edited, as that does not change that “parameterization,” not likely the case here, but I’m grasping at straws. This looks like more of a “there aren’t enough polygons to start with in the main surface to do all the holes” problem.

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So i tried reparametrize, no success…
and then i tried to tweek the mesh parameter but i get looots of faces but the problem remains…

Well I’d have to see the model to see what else could be done.

Yes i tried to upload it but it is 80mb… so i exported it in Iges
Pattern.igs (15.6 MB)
When i reimport it in rhino it seems to be exactly the same so that should be too far from the original Rhino files

Okay I opened this up and in the detailed mesh settings I didn’t do anything but crank “Density” to 1, which auto adjusts some of the other options based on the size of the object, and that seemed to make a decent mesh, about 250K polygons.

but do you get those too:

It appears not. I’ll send the file back if you can’t reproduce it.

yes that would be great thanks, but i would like to understand why it doesn’t work on mine :thinking:
Could it be something from the settings of rhino?
Do you get this weird shapes on the surface too? (prior to the conversion into mesh)

I think that for the object size and for 3d printing, those little triangles doesn’t matter at all compared to the layer definition of the printer.

I don’t know, it’s quite deep. Also i have other models with similar patterns and the similar problem so i would like to understand the problem on this one so that i can solve the other one too…

look over here
rebuild the top surface then create a solid offset.


ExtendSrf and split

OffsetSrf and fillet

Pattern.rar (9.7 MB)

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Hi Vikthor,

Thanks, it’s better.
however i think the difference between why it works on yours and jim carruthers is that you both have the flat shading not toggle and that smoothen everything…
When i toggle it, those things appears. I am not really worried about how it look like in rhino, but when i put it in keyshot or if i put i would 3D print it it is something that you would probably notice.

Also i have tried what you told me (extendsrf, rebuilt surface, retrim) and the surface looks perfect when extended and the problem seems to appear when triming or spliting…

No I looked at the mesh itself. I’ll send the file.