Author Topic: Can I acheive this in Meshmixer?  (Read 120 times)

LoopSwirly

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Can I acheive this in Meshmixer?
« on: February 12, 2018, 05:20:54 PM »
Hello everybody,
I'm an absolute newbie to Meshmixer and I was wondering if it has the capability to modify geometries that I'm interested in. If you guys think so, I'll learn how to use Meshmixer, if what I need is not possible to do using Meshmixer, could you guys suggest alternative methods/software/techniques? Details of my problem are given below:

The Geometry:
I've attached an image to this post. The geometry you see has been developed from MRI scans of patients with heart defects.

The Problem:
In the image, you'll see a portion which has been highlighted in a dashed box. In the patients I'm interested in, this portion is a synthetic graft and stays the same size, whereas the rest of the geometry outside of the dashed box are blood vessels that grow. So what I need to do is to uniformly scale up the portion outside of the box, while keeping the portion inside of the box constant and at the same time not break the mesh. I need the scaled portion of the geometry and the unscaled portion of the geometry to remain connected by smooth curves, if possible. I intend to use the final geometry to create a volume mesh that I can use for a finite element simulation.

Thanks in advance!




MagWeb

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Re: Can I acheive this in Meshmixer?
« Reply #1 on: February 12, 2018, 08:48:14 PM »
yep ( if I got you right )

Create 3 face groups via SELECT: Select a groups region and run Modify/CreateFaceGroup.
One group for the static part (magenta), one "transition" group (yellow) and one of the to be scaled region (blue).
(basically the transition group is enough for it splits the white "non group" into two regions)

Now select the to be scaled blue region (double click it in SELECT) and run Deform/SoftTransform.
Dragging the white cube in the widget's center will scale it while deforming the yellow group and keeping the magenta one as it is.
I'm just a user as you are. Being no Autodesk employee: I do not know where this road will lead to, nor do I claim to've all stuff got right.

LoopSwirly

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Re: Can I acheive this in Meshmixer?
« Reply #2 on: February 12, 2018, 09:03:00 PM »
Brilliant!That is what I need!I probably should have mentioned this in the original post, but is it possible to scale up volumetrically by a fixed factor? For example if I wanted to scale up volumetrically  by exactly 20% (i.e scale up so that the new volume is 20% greater than the original volume, while maintaining the original shape), is there a way I can specify that, by defining a scale factor perhaps?

MagWeb

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Re: Can I acheive this in Meshmixer?
« Reply #3 on: February 13, 2018, 04:40:19 AM »
Selection based transformation does not support numerical input , sorry.

So you need to do it another way:

- Select the blue group (the one to be scaled) and hit "Y" to make it a separate object.
- Select the yellow transition group and discard it hitting "X"
- Scale up the vessels object via EDIT/Transform: Make sure that UniformScaling is activated in the tool's options and double click one of the numbers in its Scale section (e.g. ScaleX). Now put in "1.2" if you want it 20% bigger, hit Enter an Accept.
- Activate both objects now (press Shift while clicking the second object) and run EDIT/Combine
- Switch to SELECT and double click on both of the open boundaries (only both boundaries should be highlighted orange now)
- This selected run Edit/Join
I'm just a user as you are. Being no Autodesk employee: I do not know where this road will lead to, nor do I claim to've all stuff got right.

LoopSwirly

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Re: Can I acheive this in Meshmixer?
« Reply #4 on: February 13, 2018, 12:19:31 PM »
Selection based transformation does not support numerical input , sorry.

So you need to do it another way:

- Select the blue group (the one to be scaled) and hit "Y" to make it a separate object.
- Select the yellow transition group and discard it hitting "X"
- Scale up the vessels object via EDIT/Transform: Make sure that UniformScaling is activated in the tool's options and double click one of the numbers in its Scale section (e.g. ScaleX). Now put in "1.2" if you want it 20% bigger, hit Enter an Accept.
- Activate both objects now (press Shift while clicking the second object) and run EDIT/Combine
- Switch to SELECT and double click on both of the open boundaries (only both boundaries should be highlighted orange now)
- This selected run Edit/Join

So I've managed to split the geometry into 2 face groups and have scaled the pink one up by 20%. However, when I activate both objects and select combine, then switch to selection, the open boundaries don't show up in orange. I've attached a picture here.
« Last Edit: February 13, 2018, 06:57:11 PM by LoopSwirly »

MagWeb

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Re: Can I acheive this in Meshmixer?
« Reply #5 on: February 13, 2018, 05:40:29 PM »
In SELECT you have to double click on the blue lines (open boundary) to select the boundary faces.

In this case (as there are only two open boundaries) you may also simply SelectAll and run Edit/Join after that.
I'm just a user as you are. Being no Autodesk employee: I do not know where this road will lead to, nor do I claim to've all stuff got right.

LoopSwirly

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Re: Can I acheive this in Meshmixer?
« Reply #6 on: February 13, 2018, 06:56:27 PM »
In SELECT you have to double click on the blue lines (open boundary) to select the boundary faces.

In this case (as there are only two open boundaries) you may also simply SelectAll and run Edit/Join after that.

That worked! Thank you. Now, before actually performing the join operation, I need to move the two facegroups close to each other. When I scale up the vessel face group, it moves away from the unscaled facegroup. What I've tried to do is select one of the facegroups then use Deform>Transform to move it around roughly by hand and then perform the join operation. The result is pretty good. Is there some way I could move the facegroups around with a little more fine control, so I could position it just right? At the moment the transform command lets me move the geometries in steps 2.5 mm only.

Thanks again!

rowiac

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Re: Can I acheive this in Meshmixer?
« Reply #7 on: February 14, 2018, 12:16:12 AM »
When you have Transform activated, click on the green "S" in the lower left corner and this will turn off Snap.  Now you will be able to move the object in very fine increments.

MagWeb

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Re: Can I acheive this in Meshmixer?
« Reply #8 on: February 14, 2018, 03:29:51 AM »
In addition to rowiac:

You could keep the boundary position of the scaled object (more or less):

With the not yet scaled object active go to EDIT/CreatePivot. Set the tool's PlacementMode option to SnapToBoundaryCenter.
Double clicking near the open seam drops a pivot to the boundary's center. Leave the tool.

Now running EDIT/Transform and clicking the pivot makes the widget snap to this position and it will be the fixed point for scaling....
I'm just a user as you are. Being no Autodesk employee: I do not know where this road will lead to, nor do I claim to've all stuff got right.