new boolean difference meshing issue with surfaces #85217

New Issue

claas eicke · 2021-01-30T03:13:30+01:00

claas eicke commented

2021-01-30 03:13:30 +01:00

System Information
Operating system: Darwin-19.6.0-x86_64-i386-64bit 64 Bits
Graphics card: NVIDIA GeForce GTX 775M OpenGL Engine NVIDIA Corporation 4.1 NVIDIA-14.0.32 355.11.11.10.10.143

Blender Version
Broken: New Boolean code - version: 2.91.0, branch: master, commit date: 2020-11-25 08:34, hash: 0f45cab862
Worked: Old Boolean code works

Short description of error
new boolean code does seem to have mesh intersection issues
when dealing with a solid it works better

Exact steps for others to reproduce the error
intersect to surfaces
add a boolean difference modifier

to make it work add a solidify modifier before the boolean modifier

Boolean Issue.blend.zip

**System Information** Operating system: Darwin-19.6.0-x86_64-i386-64bit 64 Bits Graphics card: NVIDIA GeForce GTX 775M OpenGL Engine NVIDIA Corporation 4.1 NVIDIA-14.0.32 355.11.11.10.10.143 **Blender Version** Broken: New Boolean code - version: 2.91.0, branch: master, commit date: 2020-11-25 08:34, hash: `0f45cab862` Worked: Old Boolean code works **Short description of error** new boolean code does seem to have mesh intersection issues when dealing with a solid it works better **Exact steps for others to reproduce the error** intersect to surfaces add a boolean difference modifier to make it work add a solidify modifier before the boolean modifier [Boolean Issue.blend.zip](https://archive.blender.org/developer/F9604695/Boolean_Issue.blend.zip) ![Screen Shot 2021-01-29 at 9.08.32 PM.png](https://archive.blender.org/developer/F9604692/Screen_Shot_2021-01-29_at_9.08.32_PM.png) ![Screen Shot 2021-01-29 at 9.09.24 PM.png](https://archive.blender.org/developer/F9604691/Screen_Shot_2021-01-29_at_9.09.24_PM.png)

claas eicke commented

2021-01-30 03:13:30 +01:00

Added subscriber: @ClaasKuhnen

Robert Guetzkow commented

2021-01-30 10:21:05 +01:00

Added subscribers: @howardt, @rjg

Robert Guetzkow commented

2021-01-30 10:21:05 +01:00

Without solidify the geometry is non-manifold so this might be a case similar to #84493 @howardt?

Howard Trickey commented

2021-01-30 22:40:52 +01:00

This is indeed the same general issue: Boolean is not guaranteed to work when both operands are not volume enclosing. The old boolean will have issues too in certain orientations of the mesh. The code I have been playing around with seems to do better in this case. I just need to test it more before committing.

claas eicke commented

2021-01-31 20:03:29 +01:00

@howardt I see ok so this is just a limit - period.
Maybe surfaces work maybe not

In general simply only use volumes ?

Too bad - solid modeling is great but only can get you sofar.
Sometimes you need surface trimming too.

@howardt I see ok so this is just a limit - period. Maybe surfaces work maybe not In general simply only use volumes ? Too bad - solid modeling is great but only can get you sofar. Sometimes you need surface trimming too.

Howard Trickey commented

2021-01-31 20:28:46 +01:00

If both operands are not volumes, trimming can be kind of ambiguous. You could say a difference A - B, where A, and B are both non-closed surfaces means: discard everything on the positive normal side of B from A, but I could draw lots of pictures where it is not clear what is on "the positive normal side of B", if B doesn't extend to effectively infinity. I'm sure you can image this.

If B is a closed volume, the ambiguity goes away, and I am comfortable saying that Boolean will do the expected "discard everything from A that is not inside B", which can do the trimming you desire. Other cases may work, or maybe not, no real way to guarantee.

I am about to submit code that should work a little better than the current code in situations where both are not volumes. As I said above, it makes the example in this bug work.

If both operands are not volumes, trimming can be kind of ambiguous. You could say a difference A - B, where A, and B are both non-closed surfaces means: discard everything on the positive normal side of B from A, but I could draw lots of pictures where it is not clear what is on "the positive normal side of B", if B doesn't extend to effectively infinity. I'm sure you can image this. If B is a closed volume, the ambiguity goes away, and I am comfortable saying that Boolean will do the expected "discard everything from A that is not inside B", which can do the trimming you desire. Other cases may work, or maybe not, no real way to guarantee. I am about to submit code that should work a little better than the current code in situations where both are not volumes. As I said above, it makes the example in this bug work.

claas eicke commented

2021-01-31 20:45:04 +01:00

Added subscriber: @howard