Welcome to Autodesk’s Meshmixer Forums. Share your knowledge, ask questions, and explore popular Meshmixer topics.
Showing results for 
Show  only  | Search instead for 
Did you mean: 

lasso tool complex cuts, snap to grid, plane cut alternative

Message 1 of 10
1672 Views, 9 Replies

lasso tool complex cuts, snap to grid, plane cut alternative

Good day, losing it here, sure there is a simple answer but I cant find it.

Please refer to images.


I am trying to make more complex cuts than "plane cut" along the edges of my model. I get close by selecting with the "lasso tool" but the edges need to be 90 degrees to each other and flush with the grid. Best I can manage is with "Smooth Boundary", but this still only renders curves and not the sharp edges I am looking for (corners).


I was managing this earlier by setting up a whole lot of "plane cuts", then separating + deleting the unwanted geometry, then combining the shells again. Problem with this is, its a lot of work, and shells remain lines which fill RAM like hell, slowing everything down.


I am quite sure a solution lies between these approaches, but lord knows I am not the one to find it.

All help MUCH appreciated!!!

Message 2 of 10
in reply to: jamesbeckett73

@ the PlaneCut attempt:

- if you do PlaneCut using Slice(KeepBoth) you should not have to Separate the shells. Simply do all the cuts on the source shell. Now SELECT some seed selection on each part you want to select and hit E to ExpandToConnected. X to discard those surfaces. To weld the cracks on the remaining object run EDIT/CloseCracks.

- you might also do PlaneCut using SliceGroups, do all the needed cuts that way, double click all the groups to get rid of in SELECT and discard them.


@ the SmoothBoundary attempt:

Yo can insert pins to get sharp edges. In SmoothBoundary check PreserveMeshBoundary to fix the seam. Now to set the pins set Smoothness to zero temporarily. Double click on the boundary's corners to drop a pin there. You can move the pins t by click&drag. Now set a max Smoothness, PreserveShape at zero and a high Iteration to smooth the boundary between the pins:

Ohne Titel 12.jpeg

You will not get precise 90° that way as there's no snapping functionality AND you might run into folders if you drag the pins to far (so you might need to Remesh the result). More: See the Pins section of this Help


A third way would be a Boolean attempt.

- Extrude (just a little bit to negative) the single sided shell to a solid.

- Drop a cube from MeshMix as a separate object. Transform it to hide a not needed region of the source mesh. Hit D to drop a duplicate there and move to the next brick's position. Again hit D aso until you covered all to get rid of.

- Combine all intersecting cube and run EDIT/MakeSolid on it. Set its SolidType to SharpEdgePreserve and accept.

- Activate the extruded source mesh and (with Shift pressed) the MakeSolid result as the second object.

- Run BooleanDifference

- On that result expand a seed selection on the original surface to the group, hit I to invert the selection and finally hit X to end up with a single sided shell again.


Gunter Weber
Triangle Artisan

Message 3 of 10
in reply to: MagWeb

King MagWeb, nail on the head as usual, you are a true lifesaver!

I am working with the below mentioned solution, will give a shout how it develops:


"@ the PlaneCut attempt:

- if you do PlaneCut using Slice(KeepBoth) you should not have to Separate the shells. Simply do all the cuts on the source shell. Now SELECT some seed selection on each part you want to select and hit E to ExpandToConnected. X to discard those surfaces. To weld the cracks on the remaining object run EDIT/CloseCracks."

Message 4 of 10


Having a bit of a strange artefact from "plane cut" process when "separating shells".


The red and green sections are the said arefacts - they result in an occlusion of the texture. This also effects the exported model, resulting in blank surfaces where the artefacts appeared. Odd is, they are only appearing on one of the separated shells!! (note, there should only be two shells here, and there are, but the artefacts are from "

 weld the cracks on the remaining object run EDIT/CloseCracks")

Screen Shot 2019-01-15 at 18.08.24.png

Message 5 of 10
in reply to: jamesbeckett73

Hmm, seems the red and green area somehow lost the texture. Think what one sees in your screenshot is just the group color resulting from Combine.

I can't reproduce that issue here also doing some "crazy" cutting, separating, discarding some of the areas, combining and closing cracks. In the end the texture is kept for all regions here (there may tiny cracks remaining if one did cuts on a separated piece - but there's Inspector to repair those)

Can you do some precise step by step description of the way you get that result?

Gunter Weber
Triangle Artisan

Message 6 of 10
in reply to: MagWeb

Managed to reproduce yes:

Plane cut > Slice > Separate > Combine > Close cracks

new Plane cut > Slice > Separate shells, and baaaaamm, pink bits comes only on the one shell, and erases texture!!


Screen Shot 2019-01-15 at 20.13.23.png


I will not repeat it in the future, but would be nice to be able to fix what I have, as there is a tonne of cleaning up in this file, and my machine is slloooooowwww!

Thanks so much, greetings

Message 7 of 10
in reply to: jamesbeckett73

Interesting catch of an unhandled exception:

Seems with the first step (Separating , Combining and ClosingCracks) MM keeps TWO texture maps ("partial_mapA" on the section of the source and "partial_mapB" on the section of the formerly separated part, while both point to the same image)

Now based on a second crosswise PlaneCut the Separate of the second step looses  partial_mapB of the first step on the separated part. Seems this handles one map only.


Several workaround options:

1. Use SliceGroups for PlaneCut instead of Slice and discard not needed sections based on the groups.

2. Do not Separate at all. Just do PlaneCuts (Slice) all across the mesh. Discard not needed parts by selecting connected faces and run CloseCracks when done.

3. After the first step Export to .obj and Import again (do not save as .mix as this keeps the two texture maps).

4. Do not run Combine and CloseCracks in the first step. Simply keep on cutting the separated parts until you're done. Now activate all the remaining parts after discarding not needed stuff (via ObjectBrowser) and Combine + CloseCracks in one go. Maybe there are tiny open boundaries you need to fix via Inspector.




Gunter Weber
Triangle Artisan

Message 8 of 10
in reply to: MagWeb

Wow fantastic MagWeb, 

Your work-arounds work!!

I had to redo all cuts etc, but with these measures I am able to manage,

Thanks again...

Message 9 of 10
in reply to: MagWeb

Hello MagWeb, 

Thought this might be of interest seeing as anomalies of last post, also related as a texture fall-out.


Using plane cut to cut through the depth of model (i am trying to create shells of various depths for production), any islands not connected to the main shell loose texture. I tried exporting as .obj and reimporting without luck. Quite frustrating as it is so close, and my alternative being to manually lasso large parts of the selection - time consuming.


Screen Shot 2019-01-18 at 14.12.24.png


These islands should in theory retain their texture as new shells, although don't. The texture loss occurs when committing to plane cut, before even separating shells. Incidentally, separating shells doesn't repair texture.


Thanks in advance,

Message 10 of 10
in reply to: jamesbeckett73

What you're facing isn't lost texture but wrong infills using PlanCut with an infill on an open (non watertight mesh)

If you do not need infills at all: Easily fixed by setting PlaneCut > FillType=NoFill.


If you need infills this needs some explanation:

PlaneCut can only fill regions totally included by one or two open boundary created by the cut. 

This cut creates one open boundary around the peak of the textured mesh:

Ohne Titel10.jpeg

Infills are computed properly:

Ohne Titel 3.jpeg

A cut beneath the outer contour boundary:

Ohne Titel 5.jpeg

gives a closed boundary for each of the basins. As there's no outer limit at the outer contour MM can't fill there properly and its logic breaks. Each basin is filled separately (that's what's happening in your case):

Ohne Titel 6.jpeg

But deleting the infills you'll find the texture again:

Ohne Titel 7.jpeg

To get a proper infill in such a case you need to construct a limiting surface at the outer contour. E.g something like this (selecting the outer boundary faces and moving them down via Deform/Transform). Now there's an outer limiting surface and PlanCut finds the infill logic:

Ohne Titel 8.jpeg

Ohne Titel 9.jpeg


Gunter Weber
Triangle Artisan

Can't find what you're looking for? Ask the community or share your knowledge.

Post to forums  

Autodesk Design & Make Report