Meshmixer Plane Cut

[Terrie S]

I came across how to use the "Create Pivot" tool in Meshmixer to more precisely place a "Plane Cut," but it doesn't always seem to place the pivot where I want it. My heads are in FH with nasion at x = 0 and I want to make cuts at precise distances from this point or at other known points from the origin (I have nasion at x = 0, left and right porion at y = 0 and z = 0). When I use the default pivot placement, it sometimes places it at the origin, which is perfect because I can use that or use the "Transform" tool to shift the pivot a specific distance.

 

Anyways, even with the same settings, the pivot is not always placed at the origin, so I'm not getting a cut at 0 every single time. Has anybody played with this or have a better way of getting cuts at a precise location? Meshlab has a "Compute Planar Section" which lets me take a cut at say, x = 0, but then I have to extrude it to get a printable layer.

[Dr. Mike]

Hi Terry,

Thanks for posting this question. I too have had problems with Meshmixer when I want to perform very precise cuts or moves. For most instances Meshmixer is great when cuts can be "eyeballed," or made visually. But the plane cut tool doesn't seem to have a way to be really precise about it. In these instances, I've used Blender. Basically I will make a "plane" by starting with a cube and making the dimensions something like 1000 x 1000 x 0.1 mm. Technically this isn't a plane since it has volume, but if it is 1/10 of a mm thick for practical purposes that is a plane. You can then set the exact XYZ coordinates and the XYZ rotation of the cut plane in the object parameter pane. Then, do a boolean difference to subtract the intersecting volume between the plane and my target object, effectively making a 0.1 mm thick cut through it. 

 

Blender is scriptable, and I've had instances where I have to do multiple identical cuts on multiple objects, and I've written a python script to automate moving the cutting object and performing the cuts.

 

Sorry this isn't specifically a solution for Meshmixer, but hopefully it will help you.

 

Dr. Mike

[Terrie S]

Thanks Dr. Mike! I thought about trying something like that in Meshmixer too--using a plane and then Boolean subtraction. Does the cut in Blender give you a flat surface?

 

I just searched through Slicer and found a module called EasyClip which lets you cut a 3D model, even without a DICOM volume loaded. I can enter the coordinates to cut at in the slice views and then the model is exportable. BUT my printer software is reading it all weird, so there must be some issues with the triangles or normals.

[kopachini]

Yes, that boolean action gives you flat surface.

Somethimes I have troubles with Blender and then I add cube and use Union boolean,  then delete flat surfaces of that "model" and add facet where "cut" was made. The result is the same...

[Terrie S]

Ok thanks. I might have to try that. The EasyClip in Slicer looks like it gives me a flat plane, but when I slice it in my printing software, the top layer is not totally flat. I guess I'll just have to print it and see how it looks.

 

[Terrie S]

I printed a slice I made using the Easy Clip tool in Slicer. It works but you can see the facets on the top surface (just off by one layer it seems) that are not totally flat for some reason. The filament was not super fresh so it's a messy print.