Geometry Nodes: Mesh Boolean-Union node anamoly when boolean does not alter input mesh #107969

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opened 2023-05-16 13:10:51 +02:00 by RT · 5 comments

Blender Version
Broken: Current main.
Worked: Never.

Short description of error
I was trying to see if the simulation node group would get rid of internal geometry by incrementally using the Mesh Boolean-Union node in the Simulation node group but it seems to delete some outer geometry instead.

Without Simulation Nodes:

Operating as expected without Mesh Boolean Union node enabled (creates internal geometry see red arrow) Operating as expected with Mesh Boolean Union node enabled (no internal geometry)
screenshot-May-16-2023-06-57-33.png screenshot-May-16-2023-06-58-51.png

With Simulation Nodes:

Description Show
Operating as expected without Mesh Boolean Union node enabled (creates internal geometry see red arrow) screenshot-May-16-2023-07-03-08.png
Not Operating as expected with Mesh Boolean Union node enabled (no internal geometry but missing outer geometry) screenshot-May-16-2023-07-06-20.png
It should look something like this (no internal geometry but it should have "external" geometry also see red arrow screenshot-May-16-2023-07-08-35.png

The reason I'm trying to use the boolean mesh-union node within the simulation node group is because on some large meshes the boolean mesh-union node will fail or crash blender.
#105652 (comment)

My logic is if you have to finish an entire pie in one sitting (think of a pie eating contest) it's easier to cut them up into little pieces and eat them one at a time. So I'm incrementally running the boolean mesh-union node on smaller pieces in the simulation node group to get rid of internal geometry therefore it's less likely to crash / fail like it does trying to do this all at once on larger meshes.

Exact steps for others to reproduce the error
See attached blend file: cube repeat.blend

**Blender Version** Broken: Current main. Worked: Never. **Short description of error** I was trying to see if the simulation node group would get rid of internal geometry by incrementally using the **Mesh Boolean-Union** node in the **Simulation node group** but it **seems to delete some outer geometry instead.** ## Without Simulation Nodes: | Operating as expected without Mesh Boolean Union node enabled (**creates internal geometry see red arrow**) | Operating as expected with Mesh Boolean Union node enabled (**no internal geometry**) | | -- | -- | | ![screenshot-May-16-2023-06-57-33.png](/attachments/1b32f00c-1a19-4402-b00b-4667dd9faf2f) | ![screenshot-May-16-2023-06-58-51.png](/attachments/dfa98055-d7f0-4769-abf6-1c6e145075fe) | ## With Simulation Nodes: | Description | Show | | -- | -- | | Operating as expected without Mesh Boolean Union node enabled (creates internal geometry see red arrow) | ![screenshot-May-16-2023-07-03-08.png](/attachments/2d4d7218-5bcb-4846-ae5b-3c16a1572a70) | | Not Operating as expected with Mesh Boolean Union node enabled (no internal geometry but missing outer geometry) | ![screenshot-May-16-2023-07-06-20.png](/attachments/a9610fdb-8b56-4fc2-819e-5c26b59ca0b2) | | It should look something like this (no internal geometry but it should have "external" geometry also see red arrow | ![screenshot-May-16-2023-07-08-35.png](/attachments/038b76d9-d505-42f9-89a3-181e95626ddc) | The reason I'm trying to use the boolean mesh-union node within the simulation node group is because on some large meshes the boolean mesh-union node will fail or crash blender. https://projects.blender.org/blender/blender/issues/105652#issuecomment-931240 My logic is if you have to finish an entire pie in one sitting (think of a pie eating contest) it's easier to cut them up into little pieces and eat them one at a time. **So I'm incrementally running the boolean mesh-union node on smaller pieces in the simulation node group to get rid of internal geometry therefore it's less likely to crash / fail like it does trying to do this all at once on larger meshes.** **Exact steps for others to reproduce the error** See attached blend file: [cube repeat.blend](https://projects.blender.org/attachments/f6c52fff-99d9-4ef9-a695-5cb79ca51434)
RT added the
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labels 2023-05-16 13:10:52 +02:00
Iliya Katushenock added the
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labels 2023-05-16 13:28:34 +02:00
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Can confirm the behaviour.

What I found out is if you set the X translation increment to >0.9 mm, then it works. This looks to me like it's that the boolean node outputs an unmodified mesh when the mesh isn't altered, because if you set the x too small, initially there are cubes that are fully enclosed inside the geometry, and once that happens, subsequent steps would all fail, and if each boolean step has some modification to the original mesh, it will work normally.

@HooglyBoogly @JacquesLucke may want to check this out.

Can confirm the behaviour. What I found out is if you set the X translation increment to >0.9 mm, then it works. This looks to me like it's that the boolean node outputs an unmodified mesh when the mesh isn't altered, because if you set the x too small, initially there are cubes that are fully enclosed inside the geometry, and once that happens, subsequent steps would all fail, and if each boolean step has some modification to the original mesh, it will work normally. @HooglyBoogly @JacquesLucke may want to check this out.
YimingWu added
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labels 2023-05-16 17:14:11 +02:00
YimingWu changed title from Mesh Boolean-Union node is deleting geometry when used within the Simulation node group. to Mesh Boolean-Union node anamoly inside simulation block when boolean does not alter input mesh. 2023-05-16 17:15:04 +02:00
Iliya Katushenock changed title from Mesh Boolean-Union node anamoly inside simulation block when boolean does not alter input mesh. to Geometry Nodes: Mesh Boolean-Union node anamoly inside simulation block when boolean does not alter input mesh. 2023-05-16 17:48:27 +02:00
Iliya Katushenock added the
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label 2023-05-16 17:55:59 +02:00
Iliya Katushenock changed title from Geometry Nodes: Mesh Boolean-Union node anamoly inside simulation block when boolean does not alter input mesh. to Geometry Nodes: Mesh Boolean-Union node anamoly when boolean does not alter input mesh 2023-05-20 19:18:06 +02:00
Iliya Katushenock removed the
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label 2023-05-20 19:18:11 +02:00

image
Problem is not related with simulations.

![image](/attachments/8eaea64e-98db-4236-a7c8-be8c9d8bbb94) Problem is not related with simulations.
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Iliya Katushenock removed the
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label 2023-05-20 19:31:09 +02:00
Member

If your mesh has self intersections (as these do, after joining), you need to tick the "self intersection" box on the Boolean node.

Alternatively, you could just replace the "Join Geometry" node in the first example with a "Boolean union" node with two arguments. In you more complicated example with simulation nodes, you would need a new Boolean union everywhere you want to join two cube-like things that overlap (if you don't want to use the self-intersection flag; but I don't know why you'd want to avoid that).

I am assuming that in your complicated "doesn't work" case, the input to the boolean is still a mesh that is only a collection of intersecting stretched cubes or other mesh primitives that have a watertight outer shell with no internal geometry.

If your mesh has self intersections (as these do, after joining), you need to tick the "self intersection" box on the Boolean node. Alternatively, you could just replace the "Join Geometry" node in the first example with a "Boolean union" node with two arguments. In you more complicated example with simulation nodes, you would need a new Boolean union everywhere you want to join two cube-like things that overlap (if you don't want to use the self-intersection flag; but I don't know why you'd want to avoid that). I am assuming that in your complicated "doesn't work" case, the input to the boolean is still a mesh that is only a collection of intersecting stretched cubes or other mesh primitives that have a watertight outer shell with no internal geometry.
Author

I have tried your suggestion and the issue still occurs

I have tried your suggestion and the issue still occurs
Member

#107969 (comment)

What I have found out is if there's any one step that doesn't alter the mesh (like when object being booleaned is completely inside the other one), subsequent booleans will all fail, to me it looks like that the "result" being returned from that boolean node is wrong and leading to later nodes operating on a different mesh.

https://projects.blender.org/blender/blender/issues/107969#issuecomment-941466 What I have found out is if there's any one step that doesn't alter the mesh (like when object being booleaned is completely inside the other one), subsequent booleans will all fail, to me it looks like that the "result" being returned from that boolean node is wrong and leading to later nodes operating on a different mesh.
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Reference: blender/blender#107969
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