How can I select multiple specific mesh faces at once?

Hello,

I’m working with a mesh and am currently trying to adjust the normals so that they point in the same direction. I’ve changed the color of the back face to orange and the front face to light grey so i can visualize all faces. I already used UnifyMeshNormals and this is the best Rhino could do (see image). So now i have to explode the mesh and flip all the remaining orange faces 180 degrees using Dir to flip normals.

My questions is, is there a way to select multiple specific faces so i don’t have to shift+click every single individual face?

I tried using SelColor but that didn’t work.

Please let me know if this is possible to do with grasshopper or writing some code.

Hello- can you please post a file with that mesh or send to tech@mcneel.com with a link back here in your comments?

-Pascal

Hi Pascal, here is the file
Rhino mesh.3dm (54.1 KB)

Hi Orlando - it looks like you have multiple closed objects juxtaposed and joined into one mesh:

So making all the normals wortk out will not be possible.

-Pascal

Hi Pascal, thank you for your response. Is it possible you check for the same thing with this other file i worked on previously? I managed to make the normals work out (see image) but I had to manually click on each individual face after i exploded the mesh.

Rhino mesh_2.3dm (43.9 KB)

Also would appreciate if you shared how you checked for multiple closed objects juxtaposed into one mesh.

Thanks you

Hi Orlando - that one has some of each -
image

the normals will have the same problems, presumably. How are you making these?

-Pascal

I was given the 3D models as part of an assignment in .dwg file format, this is how model appears when i open the .dwg files in Rhino7.
Generally I have to objectives, close the mesh and fix the normals. I think i did a good job with the second model I shared but you are saying that the normals will have problems. Can you specify what problems? Also I am not trying to 3D print or export anything, just edit the geometry for energy simulations.

Thanks

Hi Orlando - I’d do this - SplitDisjointMesh then UnfiyMeshNormals and Flip as needed the various parts, then, if you want, rejoin all the bits.

-Pascal

Thank you Pascal this method is much easier and quicker than what I was doing before.
Since these files have multiple objects juxtaposed, is it possible to combine them into a single object by deleting the face of one of the objects?
For example in the image you shared before, is it possible to remove the bottom face of the small box (red arrow) and merge or combine the remaining faces with the rest of the model?

image

Hi Orlando -
With boxy simple shapes like this, I’d do:

  • ToNURBS (you can delete the input)
  • MergeAllCoplanarFaces
  • Explode
  • Join

That seems to fix this last one, at any rate.
It creates two different objects that can be BooleanUnion’ed together to make a single, closed polysurface.
-wim

Thank you Wim this was very useful. Is there any way to select the surfaces sitting on top of each other without having to individually click each surface?

Hi Orlando -

Looking back at this topic, I now somewhat understand the picture that Pascal posted :see_no_evil:

Why do you want to select the faces that are sitting on top of each other?
If the aim is to create a single closed object, the BooleanUnion (or MeshBooleanUnion if you go the SplitDisjointMesh + UnfiyMeshNormals route) will automatically get rid of those overlapping faces.
-wim

Interesting, thank you Wim. I was trying to use the BooleanUnion but the command forces me to select the faces by clicking on them, i just wanted a command that would do that automatically for me without me having to manually click on the faces.

Something is wrong then. The BooleanUnion command can take both surfaces and polysurfaces.
-wim

yes, it was because i exploded the meshes to handle individual faces. I had forgotten to use BooleanUnion.