Strange shading behaviour when using boolean modifier #95913

New Issue

tempdevnova · 2022-02-20T17:49:20+01:00

tempdevnova commented

2022-02-20 17:49:20 +01:00

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 431.07

Blender Version
Broken: version: 3.0.0, branch: master, commit date: 2021-12-02 18:35, hash: f1cca30557

Short description of error
When using a boolean modifier with an object that on a target object it uses the normals of the boolean object on the target object to determine the shading on the affected areas of the target object.

Exact steps for others to reproduce the error
When using a boolean modifier with an object that on a target object it uses the normals of the boolean object on the target object to determine the shading on the affected areas of the target object.
This means, that when using a boolean object that has shade flat on a target object that has shade smooth, the resulting object will have smooth shading everywhere except where the boolean operation happens.
Additionally, when using custom split normals (like e.g. weighted normals) it applies the custom split normals on the target object.

This behavior already seems pretty strange to me, since it almost always gives strange results since oftentimes the normals from the boolean object and the target object don't perfectly match, causing weird shading issues.
I can understand that this may be an intentional feature, but it just brings so many problems, since normal editing modifiers after a boolean modifer like weighted normals don't affect the areas affected by the boolean modifier, meaning to tweak shading in these areas you have to tweak the normals of the boolean object and somehow make a seamless transition to the target object...
Apart from that it also causes some other problems, that are a worth a seperate bug report, which i will write shortly.

An additional problem with this is that shade smooth and shade flat aren't considered custom spilt normals, so after applying the boolean modifier the areas affected by the boolean modifier will change it's shading to that of the target object, since the shade smooth isn't applied as a custom normal.
For some reason that doesn't happen automatically, since directly after you aplly the boolean modifier the shading doesn't change immediately, instead it only changes when you "recalculate" the normals when using left click -> shade flat or shade smooth.

A test file to demonstrate this behavior:
Test_file3.blend

After applying the boolean modifier and "recalculating" the normals using left click -> shade flat or shade smooth the normals left from the boolean modifier will have vanished.

**System Information** Operating system: Windows-10-10.0.19041-SP0 64 Bits Graphics card: GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 431.07 **Blender Version** Broken: version: 3.0.0, branch: master, commit date: 2021-12-02 18:35, hash: `f1cca30557` **Short description of error** When using a boolean modifier with an object that on a target object it uses the normals of the boolean object on the target object to determine the shading on the affected areas of the target object. **Exact steps for others to reproduce the error** When using a boolean modifier with an object that on a target object it uses the normals of the boolean object on the target object to determine the shading on the affected areas of the target object. This means, that when using a boolean object that has shade flat on a target object that has shade smooth, the resulting object will have smooth shading everywhere except where the boolean operation happens. Additionally, when using custom split normals (like e.g. weighted normals) it applies the custom split normals on the target object. This behavior already seems pretty strange to me, since it almost always gives strange results since oftentimes the normals from the boolean object and the target object don't perfectly match, causing weird shading issues. I can understand that this may be an intentional feature, but it just brings so many problems, since normal editing modifiers after a boolean modifer like weighted normals don't affect the areas affected by the boolean modifier, meaning to tweak shading in these areas you have to tweak the normals of the boolean object and somehow make a seamless transition to the target object... Apart from that it also causes some other problems, that are a worth a seperate bug report, which i will write shortly. An additional problem with this is that shade smooth and shade flat aren't considered custom spilt normals, so after applying the boolean modifier the areas affected by the boolean modifier will change it's shading to that of the target object, since the shade smooth isn't applied as a custom normal. For some reason that doesn't happen automatically, since directly after you aplly the boolean modifier the shading doesn't change immediately, instead it only changes when you "recalculate" the normals when using left click -> shade flat or shade smooth. A test file to demonstrate this behavior: [Test_file3.blend](https://archive.blender.org/developer/F12878874/Test_file3.blend) After applying the boolean modifier and "recalculating" the normals using left click -> shade flat or shade smooth the normals left from the boolean modifier will have vanished.

tempdevnova commented

2022-02-20 17:49:20 +01:00

Added subscriber: @tempdevnova

Richard Antalik commented

2022-02-20 18:36:56 +01:00

Changed status from 'Needs Triage' to: 'Confirmed'

tempdevnova commented

2022-02-20 18:38:48 +01:00

After reading this report I think, that i have to clarifiy a little bit:

The first part if the bug report is me questioning whether the way the boolean modifier handles normals is intentional or rather a bug and me listing a few problems with this behaviour if it were intentional.

The second part is a bug that i found under the assumption, that the way the boolean modifier handles normals is intentional.

Side note: https://developer.blender.org/T95915 covers the other problem I mentioned.

Thank you and have a nice day!

After reading this report I think, that i have to clarifiy a little bit: The first part if the bug report is me questioning whether the way the boolean modifier handles normals is intentional or rather a bug and me listing a few problems with this behaviour if it were intentional. The second part is a bug that i found under the assumption, that the way the boolean modifier handles normals is intentional. Side note: https://developer.blender.org/T95915 covers the other problem I mentioned. Thank you and have a nice day!

Philipp Oeser removed the

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Strange shading behaviour when using boolean modifier #95913