Trying to extrude a surface


I’m trying to extrude a surface.
I loaded a .stp mesh file… It’s from a professional scan of my project.
1: I want to split the mesh into 3 connected meshes (to make it easier to grab the surfaces).
Currently when I grab a surface there are 10 to 12 that I have to select.
2: Once I have selected the surfaces I want I cannot extrude them… What I need to do is have another layer on top of the selected mesh in that extract 3d shape so that I can extrude it. The mesh is the foundation shape. Make sense?
3: I also have a .igs file loaded on top of the .stp with various holes that orient where the new layer will attach to the foundation layer. The holes loaded fine and are there, but how do I weld them to the .stp so I don’t keep moving them by accident?
Thanks in advance.
PS I tried Fusion 360 and didn’t get this far, Fusion 360 wont handle .igs format…


I think there’s some confusion here between meshes and (NURBS) surfaces - you seem to use them interchangeably, but they are not the same thing. You can’t extrude a mesh, nor combine it with NURBS objects.

If it is indeed meshes you are working with, you will need to use Rhino’s mesh-specific commands such as MeshSplit, MeshTrim etc. OTOH, the normal Join command will allow you to join meshes together.

HTH, --Mitch


I wonder. If surface offset would work on the nurbs side ? —Mark


maybe use MeshToNURB to convert your mesh and rework them as nurbs.
difficult to say if thats effective without seeing what you are doing.


Before doing that, read this… --Mitch


oh ic :wink: but before reading that,
one should decide wether to use rhino or not.


As a novice to the 3d world, I did not even consider the mesh to be a NURB file. I’m certain that it is indeed a .stp mesh file.
Are you saying the .IGS file is NURBS? (Which is okay with my project).
I will play with the Mesh tools later tonight.
My main goal is to make a layer/surface (that I can manipulate) on top of the mesh surface.


The mesh will stay a mesh no matter what file format you export it with, and if it’s from a scan then it’s likely to be pretty dense, so converting it “automagically” to a surface model is not going to work. So you will probably need to stick to mesh tools. --Mitch


are you trying to get rid of nurbs?

mesh is very limited, if one decides to find another way then why not to work it further as nurbs. it can be a bit complicated but then again one can also regain a lot. i cant understand your approach of trimming this possibility off.


I said “probably”… If you have a mesh format to start with, depending on what you need to do, it’s generally far easier to try to stay in a mesh format rather than spending hours trying to reverse-engineer the mesh into a usable NURBS model. Even if that means working in some software other than Rhino if Rhino’s mesh tools aren’t up to the task. However, it’s still completely unclear from the first post what actually needs to be done, so this is all theoretical BS currently.



If you want to do this in Rhino, as @Helvetosaur pointed out you will have to use the mesh specific tools. Beyond MeshSplit and MeshTrim, you might want to look at extractMeshFace, extractMeshPart, and splitDisjointMesh. Once you get them split apart as needed, you can use plain old join to joint the bits you want back together. Meshes, unlike surfaces or polysurfaces, don’t need to be touching at all to join.

Do you just want a “peg” type result, a volume were the top and bottom surfaces are the same? If that is the case, you can use copy to make a copy of the mesh where you need it, then use patchSingleFace to stitch them together. Once you have few faces stitched, try fillMeshHole to fill in the remaining open areas. I often have to try fillMeshHole, and undo when it fills poorly, try another patchSingleFace to give it a bit more guidance on how to fill, then attempt fillMeshHole again. Not the fastest or the slickest, but it does work.

As has been pointed out, this is probably because the iges is not a mesh. I’m not sure what your output goals are, but you might consider converting it to a mesh (using the mesh command) so you can join it, or patchSingleFace it to what you are calling your foundation.