I can´t delete some parts of the model?

Hi experts, I´m totally new in Rhino…

How can I delete just the legs of an internet downloaded tower without deleting some of the bars in the head?

I was able to select some parts of the bottom holding Ctrl+Shift, put then I can not delete them… What am I doing wrong?

Thanks a lot!!!

check if the objects are not blocks, to do that. deselect everything then type in the command line
SelBlockInstance. if something is selected, use Explode to convert them into normal polysurfaces. try it several time in case you have nested blocks. then you will be able to manipulate each object apart.

It’s also possible that the objects are meshes…

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if that’s the case, try with SplitDisjointMesh

Thank you guys for the immediate response!

Command SelBlockInstance dumps “No objects added to selection.”

The structure seems to be a Mesh, but command “SplitDisjointMesh” says “Unable to split this mesh. Use the Check command to verify that the mesh is valid.”

The Check command dumps several geometry error lines. The following are the general ones:

General information about this mesh:

Mesh has 230 degenerate faces.
Mesh has 452 non manifold edges.
Mesh has 200 duplicate faces.
Skipping face direction check because of positive non manifold edge count.
Mesh has 20569 pairs of faces that intersect each other.

  • This can cause problems if you’re doing mesh boolean operations with it.*

Mesh has 1659 naked edges. Naked edges can cause problems if the ultimate goal is STL output.
Mesh has 220 faces where the face normal differs substantially from the vertex normals.

  • These normals can cause problems if the ultimate goal is for rendering or boolean purposes.*

Mesh does not have any ngons.
Mesh does not have any extremely short edges.
Mesh does not have any disjoint pieces.
Mesh does not have any unused vertices.
ON_Mesh.m_F[8317].vi[] has invalid vertex indices.

The complete Check dump is here: Check_command_dump.txt (6.1 KB)

I just need to delete any non-head bar in the model. There should be a way, shouldn´t it?

Thanks again!

I guess you will have to explode the mesh to delete the polygons you don’t want manually

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Rhino is primarily a tool for modelling with nurbs surfaces. It has some mesh editing functions but these are limited. it may not be the best tool for editing your messy mesh.

However, if you want to remodel your pylon in nurbs it is capable of giving you a compact, elegant and precise solution.


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Upon using Explode command I was able to delete the not required parts. Thanks!

At this moment, I don´t want to remodel the pylon in nurbs. I just want it for some landscape in GrassHopper.

However, the bad (invalid) objects produced problems in GH. The model was loaded fine (even it could be rendered), but the bad objects were not properly processed by GH, e.g. only good objects were moved.

To solve this issue I followed some tips for bad meshes from Using Grasshopper to Fix/Simplify Complex Invalid Mesh and https://wiki.mcneel.com/rhino/badobjects

If a polygon mesh object rings up as bad, use Check command to see a more detailed report of what is wrong with it. This command tells you a good deal about what can be fixed, and you may find the commands you need among the offerings in the Mesh menu, under mesh Edit tools and mesh repair tools. Some useful commands are: ExtractDuplicateMeshFaces, ExtractNonManifoldMeshEdges, CullDegenerateMeshFaces, and UnifyMeshNormals.

In particular, _RebuildMeshNormals, _UnifyMeshNormals, Explode, ExtractDuplicateMeshFaces, and CullDegenerateMeshFaces commands were applied, but I think the later was the one that did most of the job for this pylon.

Thanks all guys, very kind, quick, and useful information!

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