Flipping Custom Split Normal Data leads to artifacts #71488

New Issue

Manuel Albert · 2019-11-11T09:20:47+01:00

Manuel Albert commented

2019-11-11 09:20:47 +01:00

System Information
Operating system: Windows 10 64bit
Graphics card: Quadro RTX 5000

Blender Version
Broken: 2.80 Official Release and late
Worked: Unknown

Short description of error
At blenderconference I had a quick conversation with @mont29 about this issue and tried to explain it as good as possible.
When you try to flip the normals of a mesh with custom split normal data it results in artifacts. I started conversation as a feature request but he said it is supposed to work and should be filed as a bug report.

Exact steps for others to reproduce the error
Based on the default startup or an attached .blend file (as simple as possible).

Go to edit mode
Object > Normals > Flip
Go back to object mode and see the result

flipping_custom_normals.blend

**System Information** Operating system: Windows 10 64bit Graphics card: Quadro RTX 5000 **Blender Version** Broken: 2.80 Official Release and late Worked: Unknown **Short description of error** At blenderconference I had a quick conversation with @mont29 about this issue and tried to explain it as good as possible. When you try to flip the normals of a mesh with custom split normal data it results in artifacts. I started conversation as a feature request but he said it is supposed to work and should be filed as a bug report. **Exact steps for others to reproduce the error** Based on the default startup or an attached .blend file (as simple as possible). 1) Go to edit mode 2) Object > Normals > Flip 3) Go back to object mode and see the result [flipping_custom_normals.blend](https://archive.blender.org/developer/F8028739/flipping_custom_normals.blend) ![3_wrong_shading.png](https://archive.blender.org/developer/F8028745/3_wrong_shading.png) ![2_flipping_the_normals.png](https://archive.blender.org/developer/F8028744/2_flipping_the_normals.png) ![1_flipped_normals.png](https://archive.blender.org/developer/F8028743/1_flipped_normals.png)

Manuel Albert commented

2019-11-11 09:20:47 +01:00

Added subscribers: @mont29, @ManuelAlbert

Bastien Montagne commented

2019-11-12 11:11:10 +01:00

Added subscriber: @ideasman42

Bastien Montagne commented

2019-11-12 11:11:10 +01:00

That this is not a bug in fact, just a TODO.

Thing is, that operator does not actually flips the normals, it only reverts the face winding, which implies a revert of the automatically computed normals, and custom normals are stored in some kind of difference from auto normals, so they do get inverted as well, but in a weird way.

@ideasman42, I think we can do two things here:

Keep current operator as-is, but probably rename it (although I guess something like 'revert face winding' would not be really easy to understand for most users), and add a real invert normal operator that would take into account clnors.
Edit current operator to become aware of clnors (basically, it’d have to store them before inverting the winding, then invert those vectors, and store them back after winding and auto-normals have been inverted).

I think option two makes more sense, just not sure whether keeping the ability to only invert winding is important or not? We could also keep it as an option of the operator (something like 'Only Invert Face Winding')?

That this is not a bug in fact, just a TODO. Thing is, that operator does not actually flips the normals, it only reverts the face winding, which implies a revert of the automatically computed normals, and custom normals are stored in some kind of difference from auto normals, so they do get inverted as well, but in a weird way. @ideasman42, I think we can do two things here: - Keep current operator as-is, but probably rename it (although I guess something like 'revert face winding' would not be really easy to understand for most users), and add a real invert normal operator that would take into account clnors. - Edit current operator to become aware of clnors (basically, it’d have to store them before inverting the winding, then invert those vectors, and store them back after winding and auto-normals have been inverted). I think option two makes more sense, just not sure whether keeping the ability to only invert winding is important or not? We could also keep it as an option of the operator (something like 'Only Invert Face Winding')?

Bastien Montagne self-assigned this 2019-11-12 11:11:25 +01:00

Stanislav Blinov commented

2019-11-12 16:32:49 +01:00

Added subscriber: @Stan_Pancakes

Stanislav Blinov commented

2019-11-12 16:32:49 +01:00

See also #47041, and its recent manifestation on BA . Blender lacks general awareness of custom normal data for tools and modifiers (i.e. from a user's perspective, flipping, mirroring, etc. should "just work" on custom normals too, and the current behavior is unexpected).

See also #47041, and its recent [manifestation on BA ](https://blenderartists.org/t/weird-shading-being-so-dark-in-viewport/1190468). Blender lacks general awareness of custom normal data for tools and modifiers (i.e. from a user's perspective, flipping, mirroring, etc. should "just work" on custom normals too, and the current behavior is unexpected).

Zsolt Stefan commented

2020-04-28 17:48:30 +02:00

Added subscriber: @ZsoltStefan

Zsolt Stefan commented

2020-04-28 17:48:30 +02:00

I was just having the same problem. Trying to invert custom normals of a mesh rotates them in a weird way. There used to be an addon (for 2.79) called Custom Normal Toolsthat could do that. It was removed for 2.80 (see here https://developer.blender.org/D3794) but was never replaced with an internal operator. @mont29 any chance for this?

I was just having the same problem. Trying to invert custom normals of a mesh rotates them in a weird way. There used to be an addon (for 2.79) called *Custom Normal Tools*that could do that. It was removed for 2.80 (see here https://developer.blender.org/D3794) but was never replaced with an internal operator. @mont29 any chance for this?

Bastien Montagne commented

2020-05-22 11:39:37 +02:00

Changed status from 'Confirmed' to: 'Resolved'

Bastien Montagne closed this issue

2020-05-22 11:39:37 +02:00

Bastien Montagne commented

2020-05-22 11:39:37 +02:00

Implemented by 516e1b4031

Implemented by 516e1b4031

Sebastian Parborg commented

2020-08-04 12:40:11 +02:00

Added subscriber: @ZedDB

Sebastian Parborg commented

2020-08-04 12:40:11 +02:00

Changed status from 'Resolved' to: 'Confirmed'

Sebastian Parborg reopened this issue

2020-08-04 12:40:11 +02:00

Sebastian Parborg commented

2020-08-04 12:40:11 +02:00

This is not fixed yet.
This seems to be an other issue than the one I fixed as simply flipping the custom normals is ok.
But when we flip both face winding and custom normals, it fails to produce good flipping results.

Normals that were not split before are split sometimes or the flipped direction is off by a bit leading to ugly shading.

This is not fixed yet. This seems to be an other issue than the one I fixed as simply flipping the custom normals is ok. But when we flip both face winding and custom normals, it fails to produce good flipping results. Normals that were not split before are split sometimes or the flipped direction is off by a bit leading to ugly shading.

Bastien Montagne was unassigned by Sebastian Parborg

2020-08-04 12:49:23 +02:00

Sebastian Parborg self-assigned this 2020-08-04 12:49:23 +02:00

Alexey Afanasyev commented

2020-08-04 13:12:55 +02:00

Added subscriber: @psychoboy852

blender-admin commented

2020-08-04 19:30:14 +02:00

This issue was referenced by e4370eccdf

This issue was referenced by e4370eccdf8e718b4d20ad6121145883407f686e

blender-admin commented

2020-08-04 19:30:14 +02:00

This issue was referenced by 0d3b5a5068

This issue was referenced by 0d3b5a50689187e574355b925225e1f909144c77

Sebastian Parborg commented

2020-08-04 19:33:21 +02:00

Changed status from 'Confirmed' to: 'Resolved'

Sebastian Parborg closed this issue

2020-08-04 19:33:21 +02:00

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Flipping Custom Split Normal Data leads to artifacts #71488