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Maniphest T94218

Delete Geometry node doesn't delete properly
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Description

System Information
Operating system: macOS-10.14.5-x86_64-i386-64bit 64 Bits
Graphics card: Intel(R) Iris(TM) Graphics 6100 Intel Inc. 4.1 INTEL-12.9.22

Blender Version
Broken: version: 3.0.0, branch: master, commit date: 2021-12-02 18:35, hash: rBf1cca3055776
Worked: Still broke on latest version

deletegeometryglitch.blend3 MBDownload


Short description of error
"Delete Geometry" node doesn't delete all the geometry. Instead it deletes a little at a time, so you need to keep repeating the node.

Exact steps for others to reproduce the error
Download the attached .blend file and unmute each of the "Delete Geometry" nodes one by one. Notice how each node deletes more geometry. Would be great if only one "Delete Geometry" was required.

Event Timeline

Hallam Roberts (MysteryPancake) created this task.Dec 18 2021, 9:21 AM
Hallam Roberts (MysteryPancake) changed the subtype of this task from "Report" to "Bug".Dec 18 2021, 9:30 AM
Hallam Roberts (MysteryPancake) added a project: Geometry Nodes.Dec 18 2021, 9:35 AM
Hallam Roberts (MysteryPancake) renamed this task from BUG: Delete Geometry doesn't delete properly to Delete Geometry node doesn't delete properly.Dec 18 2021, 9:38 AM
Hallam Roberts (MysteryPancake) updated the task description. (Show Details)
Garek (Garek) closed this task as Archived.Dec 18 2021, 12:54 PM
Garek (Garek) added a subscriber: Garek (Garek).

Thanks for the report but please do not change subtype on your own.

The problem is that with each Delete Geometry node Target Geometry of Raycast node is evaluated not based on initial MIRROR object but evaluated one with deleted geometry already. You can see that if you make Target Geometry constant by using Capture Attribute node the result will be the same (I modified your file a little to make it easier to show).

Answer for why result would be different when all you do is delete some faces lies in a fact that vertex normals are calculated based on face normals they're connected to. You can see here that moving one vertex will change normals of all other vertices, and dissolving it would affect them too.

That is also why your setup can't get rid of all geometry on the first try. With Set Position node you try to hit Suzanne with normals from MIRROR object which vetrices on the edge are different from what they were before due to deleting faces they were additionaly connected to. By preserving both Is Hit selection and Hit Position vector you can complete your setup. (I hidden Suzanne from viewport to showcase better)

So this is not a bug hence I'll close report. Coold idea btw!

Yevgeny Makarov (jenkm) changed the subtype of this task from "Bug" to "Report".Dec 18 2021, 1:16 PM
Hallam Roberts (MysteryPancake) added a comment.Dec 18 2021, 1:44 PM

Thanks for the help! I apologize for changing the subtype.