Extrude manifold creates non manifold geometry #80440
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Reference: blender/blender#80440
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System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce GTX 1080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 451.77
Blender Version
Broken: version: 2.90.0, branch: master (modified), commit date: 2020-08-31 11:26, hash:
0330d1af29Worked: Probably never
Short description of error
I have not seen this in a list of known limitations therefore I am reporting this as a bug:
2020-09-03_20-04-43.mp4
Extrude manifold tends to produce non manifold geometry if extrusion crosses an edge loop, which is in conflict of what the name of the tool suggest. One vertex connected to both closed and open edges in this way is not considered manifold geometry and also goes against common sense expectation of what kind of result this tool should provide.
Resulting geometry qualifies as non-manifold even according to Blender's own operator to select non-manifold geometry:
Exact steps for others to reproduce the error
Result: Resulting produced geometry is non-manifold:
Expected: The tool produces manifold geometry, as the name suggests.
Added subscriber: @Rawalanche
#81098 was marked as duplicate of this issue
#80661 was marked as duplicate of this issue
Added subscribers: @mano-wii, @lichtwerk
Changed status from 'Needs Triage' to: 'Confirmed'
Can confirm.
This was the thing where D5336 was really good at.
@mano-wii: do you think we can get the Extrude Manifold to match D5336 in that respect?
Added subscriber: @ugosantana
Don’t think it’s a bug... I think it’s a limitation. The https://developer.blender.org/D5336 was much more feature rich. I was hoping the current version was going to evolve into that: remove edges, faces and end is a must for this tool.
Added subscriber: @Kent-Davis
True https://developer.blender.org/T80661
Added subscriber: @grosgood
Added subscriber: @ideasman42
Changed status from 'Confirmed' to: 'Archived'
Even though this would be nice to support, it's not a bug/mistake in the code.
Closing.
@ideasman42 Why you make invalid. I already test and there BUG! Extrude Manifold have many bug!
Look what I show you there have many bug. https://youtu.be/KslV6N7uPlw
An issue of a feature which is explicitly called "Extrude Manifold" creating Non-Manifold geometry is considered "nice to support" instead of bug?
The level of mental gymnastics used on this bug tracker to justify dismissing bugs as feature request just keeps surprising me on daily basis.
@ideasman42 : would also think this is wrong to close.
Do we have another task that would cover shortcomings/issues with this tool that already covers this? If not, we should have this open (it would be reported again anyways).
@lichtwerk Yes correct your answer please open again.
Added subscribers: @Germano, @juang3d
@ideasman42 @Germano what we are seeing here is that users expect this tool to work in a way that is as it should work, and it's not working as expected, so while you may consider there is no bug in the code per-se, this should be considered a bug, it may be a design flaw on the tool or the code, but the tool is not working as expected, so probably the whole tool should be considered in a buggy state, and maybe even remove or relocate it under the experimental options in the next point update of 2.90.x because it's not working as expected at all.
Keep in mind that no matter if the code works as expected, that does not make the tool to work as expected I'm afraid :S
We do use Blender 2.91 Alpha daily build I always download daily. I can see still bug
Added subscriber: @Ace_Dragon
The idea of user-expected behavior merely being a nice to have, is a very FOSS thing that I thought would start to go away now that the BF has over a million dollars coming in annually for development.
I know Germano has a patch that provides a significant improvement to this tool, which will be great when it lands. I also acknowledge the the tool is already useful in many cases. However, the BF in its marketing and announcements has made it clear that they want Blender to be seen as a software for professionals, and to succeed in that requires making polish a priority.
EDIT: Agree, better not go off-topic here, sorry.
Use this thread to talk about this problem:
https://devtalk.blender.org/t/manifold-extrude-not-working-as-expected-maybe/15112
Added subscriber: @rjg
Changed status from 'Archived' to: 'Confirmed'
@lichtwerk I agree, the operator should not produce non-manifold geometry or it should be given a different name.
@ideasman42 I'm setting the ticket status back to Confirmed. The implementation of the operator does not match the description. IMHO even if this issue is a known limitation of the current implementation the ticket should be left open as a ToDo.
@Ace_Dragon While I understand the frustration, please avoid going off-topic.
Changed status from 'Confirmed' to: 'Archived'
There has been plenty discussion and feedback in the meantime, both on the linked DevTalk thread and on the Blender-Coders channel. I hope this exchange helps to improve the development process to incorporate user feedback early on and document/communicate limitations better.
While I still agree with the criticism of the current implementation, I'm in no position to overrule @ideasman42 decision to close this ticket. Hence, I will restore the previous ticket status. This doesn't mean the issue is forgotten. All developers involved in the implementation of this feature are subscribed to this ticket or have been tagged in the discussion on Blender Chat. If I'm reading the proposal in #75913 correctly, there are already further improvements planned.
@rjg That again you put invalid why?
Did you read I show you youtube?
Regarding closing this issue. We already have #75913 (New tool to add and subtract prismatic volumes), don't let closing this be misinterpreted as being ignored.
Note that extrude-manifold does not perform the kind of boolean operation users might want/expect when extruding into existing geometry.
Even if this exact case is handled (overlapping with a subdivided cube), we will still run into cases where one half of the face overlaps, the other half not. Making the fix for this issue more of a workaround.
Where it would be trivial to make simple examples that still fail.
Time spent on some special case detection is probably better spent on #75913, although I'll double check with @mano-wii.
The issue is that it's been originally closed as invalid, not closed as resolved, and labeled as "nice to have" instead of bug. If the user expected behavior of the tool which is literally named after what it should do not being met can be categorized as nice to have instead of bug, then it sets a precedent where it's borderline impossible to report bugs for Blender as it's just impossible to tell what is one.
Here's an analogy: Imagine a "Extrude Face" operator, which upon execution, would only create new 4 vertices at the specified extrusion depth, but would not generate new triangles to form surface between and among the original 4 and new 4 vertices. Upon reported as a bug, this bug report would be closed as invalid because Extrude Face operator actually creating faces is a "nice to have" feature request, not really a bug, and there's a "feasible" workaround of user selecting sets of vertices themselves and using the Fill operator.
Handling of this bug report falls exactly into the same category.
Added subscriber: @Massivetree
Also, it may be worth considering that extrude the geometry through the end of the mesh(at which point it seems to flip the normals), it should just remove that geometry all together. So you could essentially punch holes through the mesh with the tool.