Boolean Union not working on this model  1-20  21-24

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 From:  Nicolinux
7667.1 
Hi,

Another day, another n00b question :)
I have this model that was a solid before. I had to delete two faces in order to fix a hole. But this also deleted the inner part of the hole and the model is not water tight. I extruded one edge and thought that I could simply select everything and bool -> union. But MoI just sits there calculating and won't finish. There is clearly something wrong with the model. I'd like to ask how one does debug this kind of problem? Where do you begin and what are you looking for?

Thanks,
Stefan





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 From:  Michael T. (MICTU_UTCIM)
7667.2 In reply to 7667.1 
Hi Stefan,

I was able to join the surfaces together, and found some naked edges. See the yellow highlighted edges below. Calls out 6 edges. Hopes this helps.







Michael T.
Michael Tuttle a.k.a. mictu http://www.coroflot.com/DesignsByTuttle
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 From:  Mauro (M-DYNAMICS)
7667.3 
agree with Michael
As general rule,after checked your model:
before extrude,keep your 2d lines clean,using just points you need to do the shape
so,you will not have unuseful seams like these(this part of contour should have 4 points,not 6)


M
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 From:  Michael Gibson
7667.4 In reply to 7667.1 
Hi Stefan,

> I'd like to ask how one does debug this kind of problem? Where do you begin and what are you looking for?

So like the others mention above the thing you want to look for are "Naked edges" - those are edges that belong to only one surface instead of being joined between 2 surfaces.

Areas that have naked edges break the "water-tightness" of the object's skin and those are the spots that will need to be repaired in order to make the object a full solid.

In order to see the naked edges you have to set up a shortcut key with a script on it as described here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=6051.2

Once you set that up, push the N key to get the naked edges highlighted and then you can zoom in to those areas to closely inspect the model there.

Please let me know if you are still stuck!

- Michael
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 From:  Nicolinux
7667.5 
Alright, thank you everybody. It worked, the model is fixed :)
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 From:  Nicolinux
7667.6 
Hi,

I have a little followup on this issue. This time I tried to isolate one part from the model in order to export it and test-3d-print. I created a square, extruded it down and then did an bool -> isect on the main part.




The new object is a solid but as soon as I exported it to .stl, I saw in the preview that there something very wrong with it.


I have hidden the top, and I can see that there are superflous faces that don't belong there (color blue).


I deleted those but then I was left with these edges that I can not remove.


It gets a bit more complicated because there seems to be more edges close to each other.



What could I do in such a case?
Thanks again.

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 From:  Michael Gibson
7667.7 In reply to 7667.6 
Hi Stefan, the 3DM file in your last post above appears to be empty, can you please upload one with your problem object in it?

- Michael
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 From:  Nicolinux
7667.8 In reply to 7667.7 
Michael, I think I've hit a bug in MoI. When I select this isect (solid object) and do an export, it creates the 6kb file. I had to "save as" the entire file in order to produce a proper .3dm file.
I have attached both files (the small one, and the latest with the part "saved as").

Thanks.

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 From:  Michael Gibson
7667.9 In reply to 7667.8 
Hi Stefan, I'll be looking at your geometry in just a bit, but re: this part:

> I think I've hit a bug in MoI. When I select this isect (solid object) and do an export, it
> creates the 6kb file. I had to "save as" the entire file in order to produce a proper .3dm file.

In the "Save As" file, it looks like all the objects are hidden. When you do a File > Export, only selected objects are written to the file, and hidden objects are not selected.

If you wanted to only write just one single object, you would need to show it, and then select it before doing the Export. If you hide it before doing the export it will become hidden and also unselected and so won't be exported.

Hope that makes sense, let me know if it doesn't.

- Michael
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 From:  Michael Gibson
7667.10 In reply to 7667.8 
Hi Stefan - so as far as the geometry goes the problem seems to be these collapsed slit-like openings here:






Those have 2 vertical planes attached to them, with the planes stacked up right on top of each other, overlapping the same exact space. At one point did you possibly have 2 lines in those spots duplicated right on top of each other and then joined to each other? It looks like something like that anyway.

That kind of hole that has opposite sides touching each other is a type of degenerate trimming boundary and so they will need to be removed - the way I'd try to remove them would be to delete the vertical planes and then do an "untrim" operation on the slit boundaries to remove them. There is some information on untrim here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=444.4

I'll see if I can clean this up for you by doing that.

- Michael

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 From:  Michael Gibson
7667.11 In reply to 7667.9 
Hi Stefan, also another problem I found when digging into it - this really skinny vertical fragment sticking up out of this internal plane here:





- Michael

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 From:  Michael Gibson
7667.12 In reply to 7667.11 
So those very skinny long spikes kind of complicate the cleanup, the pieces that the skinny spikes are emerging from have to be cleaned up as well.

- Michael
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 From:  Michael Gibson
7667.13 In reply to 7667.8 
Hi Stefan, I've attached here an edited version of your object with those degnerate "slit" boundaries removed and those little thin spiky fragments cut off, this version should work better for you now when cutting off a chunk to do a test print.

Hope this helps, - Michael

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 From:  Nicolinux
7667.14 
Many thanks - that was very helpful. I was able to export that part and will print it now.

Regarding my statement about the bug - I still think there is something wrong. When I selected the part to be exported, it was visible. That's how I saw in the preview that it was broken. But the exported file was still "empty".
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 From:  Nicolinux
7667.15 
The reason why this part is so messed up is because it was first designed to fit an aluminium extrusion that had the wrong size. After I had found a .step file for the correct part, I imported it and thought first to "fill" the area with the wrong sized cutout in order to cut out the new aluminium extrusion. I did this with a square that was extruded down and then merged into the main object. The thin lines with the two faces attached to them were some artifacts of this (probably silly) change that I introduced.
I think it would have been better to separate the main object and then delete the faces and edges of the cutout in order to have the cutout filled up.
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 From:  Michael Gibson
7667.16 In reply to 7667.14 
Hi Stefan,

re:
> Regarding my statement about the bug - I still think there is something wrong. When I
> selected the part to be exported, it was visible. That's how I saw in the preview that it
> was broken. But the exported file was still "empty".

I'm not able to repeat that bug over here... Here's what I did - I opened up your "broken_after_isect3.3dm" file that you attached above, then clicked Edit > Hide to show objects since they are all hidden to start with, then selected one of the large pieces and did File > Export to a test 3DM file, and then when I opened that file it had the object in it as expected.

Did it happen with a previous saved version of this file? If so can you please send that one to me so I can try to reproduce the bug over here?

I won't likely be able to fix the bug unless I can reproduce it.

- Michael
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 From:  Nicolinux
7667.17 
Yes it did. I have uploaded an unlisted Youtube video:
https://youtu.be/Q3la-k24Pxo


And I have attached the original file here.

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 From:  Michael Gibson
7667.18 In reply to 7667.17 
Hi Stefan, thanks for posting the file and the video. I am able to reproduce that bug over here now - it seems to be due to the intersected solid being malformed probably because of those doubled up faces. The object ends up with a broken region where the "is void" flag is set for both the exterior and interior regions, and when MoI goes to write an object it wants to go through the solid (is void == false) region but doesn't find any solid pieces.

It looks like it's not just File > Export that fails, File > "Save As" doesn't write the intersected piece either.

So it seems that the bug is in the boolean intersection calculation but it will be difficult to fix because booleans can get confused in general when an object has self intersecting pieces...

A couple of tips from the video - if you want to show only the one named object a shortcut for doing that is to go its entry in the scene browser and right-click on the eye. The right-click on an eye hides everything else other than that one object so that saves the step of separately hiding other things.

Also when you do a boolean you can just do it using the rectangle curve, the booleans will automatically extrude it out as needed during so you don't have to extrude it as a separate step, unless you want to make it go to a limited depth instead of all the way through.

- Michael
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 From:  Nicolinux
7667.19 In reply to 7667.18 
Alright, thank you for the tips Michael. And good luck with the bug.
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 From:  Nicolinux
7667.20 
Sorry for hijacking this thread again. I'd like to ask for advice on the best practice for this scenario.




I have the orange part where I did a cutout of the v-slot (the grey part). After I printed a small portion of the orange part (the one with the cutout) I realized that the cutout is too narrow. So I need to enlarge the coutout. My actual workflow looks like this:
1. Enlarge the grey part.
2. Fill up the cutout on the orange part (hardest step because it is prone to errors and can produce a malformed solid).
3. Do a bool diff of the grey and orange part.
4. Print

Is there a way to streamline steps 1-3? Ideally I'd only like to enlarge the cutout or maybe find a way to fill up the cutout without breaking the orange part :)

Thanks again!
Stefan
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