Author Topic: Meshmixer 3.1 Remesh gives disconnected boundaries  (Read 86 times)

Paul_W

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Meshmixer 3.1 Remesh gives disconnected boundaries
« on: April 16, 2017, 08:46:02 PM »
The new version has a bad issue with open boundaries after remeshing.  I had this in a larger model so I tried a simple test:

I imported the bunny, selected an area and remeshed 20% (all other settings default) and clicked Accept.  Now there are multiple open boundaries at the border!  (see Bunny1.jpg)

This did not happen on my previous version 3.1.148 Beta.

Close cracks does not fix any of these.
Inspector shows a big hole (see Bunny2.jpg).

Decided to try a fresh install.
When uninstalling it said Meshmixer 11.1.373
I re-downloaded Autodesk_Meshmixer_v3p1_Win64.exe  (same file version) and re-installed - on Windows 10.

Performed the same test - exact same result.

Tried to Bridge this in a small area, 1 triangle above, 4 contiguouss triangles below and it crashed (see bunny3.jpg).  Note: this particular crash is frequent in earlier versions also!

Erase and fill worked, but that's a last-ditch fix for this - not applicable in all cases.
« Last Edit: April 16, 2017, 09:43:29 PM by Paul_W »

MagWeb

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Re: Meshmixer 3.1 Remesh gives disconnected boundaries
« Reply #1 on: April 17, 2017, 03:30:18 AM »
You're right. This changed with beta 281.

Performing a partial remesh changing the density, results in the problem to join dense and less dense areas.
3.0 did this by very small faces at the boundary (which is ugly meshing if you perform other action as sculpting...);
Beta 148 did some density transition towards the remeshed area automatically (no way to avoid it);
Beta 281 + and 3.1 release do no transition automatically any more (as long as you do not allow it) at costs of open boundaries. But as you allow a small transition (note the transition slider) it should stitch the regions the same way as beta148 did.
Seems to me the current solution isn't that bad for it allows the user to decide.

If you do not allow Transition:
CloseCracks can't work for there are more vertices on the denser side. CloseCracks needs redundant vertices on both sides of the seams
Red marked areas in Inspector mean that it can#t solve the error without modifying the existing triangles around. If you think of these errors on your result as holes one would need triangles with zero surface area (which again is bad meshing) to fill them. To avoid zero area faces Inspector prefers to change the geometry around the hole.
Don't know why Bridge does not work (I can reproduce that crash). Maybe it tries to avoid zero area faces as well? Have to look into 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.

Paul_W

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Re: Meshmixer 3.1 Remesh gives disconnected boundaries
« Reply #2 on: April 17, 2017, 01:16:24 PM »
Ah, thanks for looking into that!
A 1mm transition seems to be enough to avoid the problem. 

Note that the "Show Object Open Boundaries" checkbox in Preferences does not save, so even experienced users will generate open boundaries without knowing it.  By then, sadly, it may be too late to fix easily.

I'm trying to determine what the best way to notify the user about this new "feature". 

1) Perhaps add a note below the Accept/Cancel buttons:  "Open boundaries will be generated as not enough transition was specified." 

2) Show the open boundaries in blue in the preview (even if the Show Open Boundaries checkmark is not checked).

3) Default to a 1mm transition (along with at least one of the other notifications)

4) Or maybe a checkmark in preferences "Never generate open boundaries when remeshing".

Edit: The more I think about it - I really think that no function should generate defects when using the default options.

BTW, I always save very very frequently when using the Bridge function - that crashes a lot!   
« Last Edit: April 17, 2017, 01:19:27 PM by Paul_W »

AzDesertRat

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Re: Meshmixer 3.1 Remesh gives disconnected boundaries
« Reply #3 on: April 19, 2017, 06:27:13 PM »
I'm sorry but what the heck is going on with these new versions of Mesh Mixer with critical tools being suddenly nerfed??? 

This open gap problem is completely unacceptable IMO.  What made MM special was it's dynamic triangulation while sculpting but now the mesh is constantly corrupted by gaps everywhere!  The tiny faces being auto-added where gaps now occur were easily cleaned up with a simple large selection of the area and quick remesh.  However, now the remesh tool doesn't work properly across shape borders.  Instead, the borders are littered with overlapping triangles.  In older revs these could easily be resolved by drawing a selection across both sides of the border and running remesh.  I have heavily relied on this magic ability of MM for years now to sculpt and remesh to maintain a clean topology in a fluent work flow.  The new 3.1 and 3.2 builds are unusable.

Fortunately, I can revert back to older revs that are reliable until something is done with this new, broken gen of Mesh Mixer.  Very sad to see this happen to such great software:(.
« Last Edit: April 25, 2017, 12:32:07 PM by AzDesertRat »