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Boolean Operations on two Objects
Closed, InvalidPublic


System Information
Operating system: Windows-8.1-6.3.9600 64 Bits
Graphics card: GeForce GTX 980/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 431.36

Blender Version
Broken: version: 2.80 (sub 75), branch: master, commit date: 2019-07-29 14:47, hash: rBf6cb5f54494e
Worked: (optional)

Short description of error
If you have two objects and use the boolean modifier on both objects, the operation breaks

Exact steps for others to reproduce the error

-Create two meshes

-Add the boolean modifier to both objects created

-In the boolean menu -> select the object (and do the same thing with the boolean modifier on the other object)

-Move one of the objects (sometimes it only happens with a specific one) -> (visual) artifacts apear (modeling breaks)

  • I know that this might not be considered as a bug, but it would be really sweat if you could, for example, get an object that is made of two objects intersecting.

Event Timeline

Have you tried with the latest blender build? youre using 2.80 wich is not up-to-date.
Also can you provide a simple .blend file where to proplem occurs? cant reproduce it.

Julian Mohr (Jules) changed the task status from Needs Triage to Needs Information from User.May 16 2020, 10:04 PM

I know that this might not be considered as a bug, but it would be really sweat if you could, for example, get an object that is made of two objects intersecting.

What I believe you're describing is the kind of thing that occurs when you take on cube and give it a boolean modifier and select the other cube and change the operation mode of the boolean modifier to "Intersect". This will turn the cube into a mesh that's only where the two cubes intersect.

As for the issue you're describing with the glitching, that will need to be reviewed by a developer. I can see this report going two ways:

  1. A patch is implemented so that mesh "A" can't have mesh "B" as it's boolean if mesh "B" has mesh "A" as it's boolean.
  2. This is marked as a known issue.

Thank you both for the quick response!

  1. @Julian Mohr (Jules) :

Im currently using blender via steam which I don't think updates smaller builds and currently can't test the newer ones.

  1. @Alaska (Alaska) :

Yes pretty much what you said is what I meant. This is however not just a problem with intersect but also difference (and maybe even union).

With my limit knowledge on the topic, it's probably something that would take a large bit of development effort. I wasen't aware that this is already a known issue (if I understand you correctly). Something like you mentioned (1.) would be really great though!

Cheers & Thanks!

If you need further information and a blend file to reproduce it I can obviously upload my 2.8 file.

Julian Mohr (Jules) changed the task status from Needs Information from User to Confirmed.EditedMay 17 2020, 2:05 PM

okay after messing a bit with the booleans im able to reproduce it.

Setting this to confirmed.

Like @Alaska (Alaska) said this needs developer attention

@Howard Trickey (howardt) or @Hans Goudey (HooglyBoogly) your thouhts on this?

I agree it should be fixed, but seems low priority since why would anyone realistically want to do this in the first place?

never seen a usecase under such condissions

Hans Goudey (HooglyBoogly) claimed this task.

but it would be really sweat if you could, for example, get an object that is made of two objects intersecting

I'm not exactly sure what you mean by this, why not use one boolean modifier with the Intersect operation?

Either way though, this situation is a dependency cycle, where each object depends on the other's geometry data and location:

Dependency cycle detected:
  OBCube/Geometry Component/GEOMETRY_EVAL() depends on
  OBCube.001/Geometry Component/GEOMETRY_EVAL() via 'Boolean Modifier'
  OBCube/Geometry Component/GEOMETRY_EVAL() via 'Boolean Modifier'
Detected 1 dependency cycles

We can't support dependency cycles like this, but there is a patch to display them in the UI when they are created, D4730. It needs some work before it can make in into master.

I wonder if the bug reporter is simply try to get the intersection of two objects, which is exactly what you get when you only have one object intersected by another (no need for doing it in the reverse direction. It can look like you are not getting the intersection because the intersection object remains there, unaffected, in the viewport. The intended workflow is to either delete the intersection object after making the intersection (if using the boolean tool), or to hide the intersecting object (hit the eyeball beside it in the outliner to make it non-visible).

Um well actually what I wanted to do might not be really what blender is primarely intended for but something I wanted to test. It would take a long time to elaborate what specifically I intended to do. But I was trying to use scripts to make a lot of objects and having multiple overlapping meshes make one larger one with boolean operations. However it would be a larger undertaking to keep track of where objects are and which intersect making a manual approach like you proposed Howardt unfeasable. And since I would have intended to let objects move around, just applying booleans wouldnt work either. Thanks for all the info on the topic though!

I understand the desire for a Boolean that intersects many meshes at once, and may end up making such a thing in my rewrite of Boolean that I am currently engaged in. Though it won't be the first priority to get working.