Moving 2d curves can flip shading normals #51350

New Issue

Campbell Barton · 2017-04-29T16:26:58+02:00

Campbell Barton commented

2017-04-29 16:26:58 +02:00

Simply moving a 2d curve (in edit-mode or using a shape-key) may flip its normals.

In the attached file play the animation and notice the shape-key flips the normals to those matching the 2 planes where the normals each point in different directions.

Note that this only seems to impact the shaded normal, not the face winding since the faces don't vanish when backface culling is enabled.

2d_curve_flip_bug.blend

Simply moving a 2d curve (in edit-mode or using a shape-key) may flip its normals. In the attached file play the animation and notice the shape-key flips the normals to those matching the 2 planes where the normals each point in different directions. Note that this only seems to impact the shaded normal, not the face winding since the faces don't vanish when backface culling is enabled. [2d_curve_flip_bug.blend](https://archive.blender.org/developer/F580355/2d_curve_flip_bug.blend)

Campbell Barton commented

2017-04-29 16:26:58 +02:00

Changed status to: 'Open'

Campbell Barton commented

2017-04-29 16:26:58 +02:00

Added subscriber: @ideasman42

Campbell Barton changed title from ~~Moving 2d curves may flip their normals~~ to Moving 2d curves can flip shading normals

2017-05-01 07:43:58 +02:00

Joel Godin commented

2017-05-11 03:47:17 +02:00

Added subscriber: @FloridaJo

Joel Godin commented

2017-05-11 03:47:18 +02:00

Confirmed.
Shading inversion seems to be for solid viewport shading, and rendered viewport shading sees no change.

Confirmed. Shading inversion seems to be for solid viewport shading, and rendered viewport shading sees no change.

Sebastian Witt commented

2017-05-17 19:10:06 +02:00

Added subscriber: @SebastianWitt

Sebastian Witt commented

2017-05-17 19:10:06 +02:00

It seems like your curve is not 2D. Normally curves get flattened when switching from 3D to 2D.
Contrary to that, if a curve contains Shapekeys, the keys do not get flattened.

This results in unexpected behaviour like flipping normals because the shape is not 2D but 3D.
Should Shapekeys be flattened when switching to 2D?

It seems like your curve is not 2D. Normally curves get flattened when switching from 3D to 2D. Contrary to that, if a curve contains Shapekeys, the keys do not get flattened. This results in unexpected behaviour like flipping normals because the shape is not 2D but 3D. Should Shapekeys be flattened when switching to 2D?

blender-admin commented

2017-05-26 11:03:30 +02:00

This issue was referenced by f78ba0df02

This issue was referenced by f78ba0df02a9734740d7ccddbe315020f56852f6

Campbell Barton commented

2017-05-26 11:07:21 +02:00

Changed status from 'Open' to: 'Resolved'

Campbell Barton closed this issue

2017-05-26 11:07:21 +02:00

Campbell Barton commented

2017-05-26 11:08:59 +02:00

@SebastianWitt, thanks for finding the cause (Z values in 2D curve), committed fix - no longer checks Z values.

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Moving 2d curves can flip shading normals #51350