Bad mesh --- good polysurface?

Hi I am trying to send to 3d print a file. The polysurfaces doesnt have any error…when I convert to mesh…some of the pieces show me errors.

Is it possible to know what is hapenning ?


Fitting a mesh to a polysurface is a process. You have control over the settings. Starting with a good polysurface generally results in a good mesh but not always. Starting with a bad polysurface will never result in a good mesh.

The prudent thing to do is to start with a clean, closed polysurface.
Make your mesh according to the settings you need.
Hide the polysurface, and Check the mesh. It will usually be good but not always. When the mesh has problems, use the tools in Rhino to make it good.
Then export that good mesh.

The polysurface seems ok ! pass the analysis. How can i repair a mesh?

Mesh Repair Tools – top menu bar…

Ok thanks. I am trying to decode from the error window…which tool use.

What does the error window say?

Most ‘repairs’ are done with mesh repair tools Fill hole or fill all holes.

one of the pieces says "Here is what is wrong with this mesh:
Mesh has 2 non manifold edges.
Mesh has 1 duplicate face.
Skipping face direction check because of positive non manifold edge count.

In grey the bad ones…

The Help article for Check is a good, quick overview.
If you need a more detailed tutorial, the Scan, Cleanup, Remodel white paper is good.

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This Scan, Cleanup, Remodel paper is very helpful. Really suggest you guys take a read! Thanks John.

Now for my silly question. I have a gazillion mesh objects in my file (almost all imported). Said file is now 5GB and is taking a good 20 minutes to save - very unproductive and frustrating. I’m hoping that if I clean up the mesh objects that will solve the slow saving issue. I didn’t really care if the meshes were bad as I do not plan to 3D print but now with the slow saving issue, I may have to fix them. I also have a lot (more than 200) blocks in my file to keep the size down and many of them are from meshes. When I run check on the blocks they come back as good but if I were to explode the blocks and run check on the meshes, they come back as bad. Do I have to explode all my blocks or is there a way to identify bad meshes that have been ‘blocked’?

Hello - are you blocking the meshes because they are reused multiple times in the same file? In any case double-click on a block to BlockEdit. and then select the mesh while in BlockEdit and run Check.


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Yes. I block objects that are re-used several times. Thanks for the tip.

Hi, where is this pdf? Thank you! Scan, Cleanup, Remodel / Check

Hi Sandra -

You can download that from here: Rhino - Download - Scan, Cleanup, Remodel (