Working with heavy meshes is still absolutely painful. MeshTrim, SubSelection, vertex deletion, etc

Hi McNeel team,

We are working on meshed geometry, car interiors, fully detailed down to the leather and stitches. I want to cut a section of the car (meshes) to do a CMF swatchbox. Rhino V7 can’t achieve the most basic tasks needed here. Mesh trim makes complete messes in some parts, mesh boolean fails, Shift-subselect vertices and hit delete does nothing after ling “(not responding)” periods. This is sad.

Any of you want to look at thee files and workflows? because what the tool is doing now is unacceptable.



Hi Gustavo - Mesh intersecting is undergoing an overhaul but the new stuff is not in V7 tools yet, as far as I know, apart from MeshIntersect itself as a command to get the curves of intersection.


hi Pascal, RMA team,

Related to my post of multiple paint points, we have one specific problem that keeps coming up: we are still having lots of mesh intersector issues (in V6 and V7), not only we have these issues in manual modeling and booleans, but also when we are trying to split mesh with mesh in Grasshopper.

We are realizing that we spend almost as much time trying to get workarounds to make our definitions work, as we do doing the actual value-added work of industrial design and computational modeling.

What’s your timeframe to have a better mesh solver/intersector/engine? Is this an important and prioritized problem in your team? or are we trying to work with something that will not get better anytime soon?



The plan is to have these tools improved for V7 release, so sometime between now and then.

Thanks John, do you have a non-committal sense/hunch/opinion/intuition of what that time frame looks like? are you hoping to release V7 in a few month? end of the year? next year? 3 years?

I really don’t. Our current push is V6 Mac. The developers not working on Mac V6 are working on V7. I don’t remember which developer is working on mesh intersection tools, but that’s where the heart and soul of mesh improvements will come from.
The embarrassing state of the mesh tools in Rhino has been at the top of the complaint list for tech support for quite some time.

@piac Is working on this. Nothing is in V7 yet, but stay in touch with him.

I am working on this and have something that works in Rhino 6 on a Windows machine 99% of the time on my large meshes with 18M faces where Rhino’s Mesh Tools -> Trim Mesh fails over 90% of the time. I am in the last stage of fixing it up for the few remaining known issues I have identified. It works best on triangular meshes but I am starting to get it working better on mixed triangular/quadrangular meshes. It is a Python script along with a DLL (optional) for speeding up volume/area calculations. I packaged it in an Eto GUI:

It uses a closed line as the trimming boundary. Currently you cannot cut outside the boundary of the mesh but this could be fixed. You can enter points for the boundary line, select an existing line or reuse the previous line stored on the Corners layer.

Here is a cutout from a 18M face mesh:

This mesh has 18M faces as illustrated by this wireframe-view closeup of cutout above:

The main procedures in the script are shown below:

The script moves your original mesh onto the Start Layer and uses other layers to save inputs (the boundary curve) and results (the trimmed mesh):
I would like to try this out on one of your hardest to trim meshes. If you could send me a link to the .obj file for the mesh then I could make sure it works and then release the Python script (about 3600 lines with over 50% comments). It would also be helpful to know exactly what type of trimming operations you need to perform. Do you want to trim, like in my example above, or make a hole or make a trench (with sides and bottom filled in)?


Good to know @bobmcneel , today we added some mesh reduction and other grasshopper ‘batteries’ and things are behaving better, but still when we are in the zone and designing it’s kind of frustrating seeing things full falling apart.

@piac, we can send you some examples if you need them to see where our mesh operations become problematic, especially in situations when we know they should behave. When things do not have to work in realtime we have been exporting our meshes to Nettfab and doing booleans there, but when we do need a mesh cut/intersect/boolean to make a design decision based on ‘live inputs’ this is not an option.

@Terry_Chappell, all,

We are using mesh to mesh intersections by projecting 2D curves or pulling 3D curves to mesh (in this case a shoe last), and then creating normal mesh ribbons to cut the mesh to make sections of fabric.

Like this:



1 Like

It looks like a100% quadrangular mesh with quadrangles that have curvature. I have no ideal what my script would do with these. Would be interesting to try out. Can a mesh like this be exported to .obj format? If so please send me an example. The mesh does not look like it has 18M faces like my typical meshes so maybe the .obj will not be too big. Of if that does not work, you could try a .3dm file. A link to Google Drive has been working with other forum members for transferring files to me.

The 2 inputs: last + the trimming ribbons are all quads. Their intersections do create a lot of triangles of course. I’ll need to come up with an example that fails in Rhino/GH and I’ll send you that. I’ll happen on Monday most likely.



Looking forward to it.