Mirror threshold too high, values less than 0.00002 are snapped to center #79211

New Issue

p-tone · 2020-07-24T02:06:21+02:00

p-tone commented

2020-07-24 02:06:21 +02:00

System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce GTX TITAN X/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 431.60

Blender Version
Broken: version: 2.83.3, branch: master, commit date: 2020-07-22 06:01, hash: 353e5bd749
Worked: 2.79b

Short description of error
Blender 2.8x has a bug that forces it to snap to the YZ plane with a value less than 0.00002.
The above is occurring with the snap off.
The bug occurs even if the vertex's X coordinate is moved to more than 0.00002.
Duplicating the object does not eliminate the bug.

Exact steps for others to reproduce the error
3D Viewport / Edit Mode.
Create an object with the following vertices:

Object-1 = {
  Vertex-A x =  0.00002, y = 0.00005, z = 0.0
  Vertex-a x = -0.00002, y = 0.00005, z = 0.0
  Vertex-B x =  0.000019, y = -0.00005, z = 0.0
  Vertex-b x = -0.000019, y = -0.00005, z = 0.0
}

3D Viewport / Edit Mode / Tool / Options / Mirror X [enable].
3D Viewport / Edit Mode / Snap [disable].
Select Vertex-A and Vertex-B.
Move Vertex-A and Vertex-B.
Blender 2.8x has a bug that forces it to snap to the YZ plane with a value less than 0.00002.

3D Viewport / Object Mode.
Duplicate the Object-1 to obtain the Object-2.
3D Viewport / Edit Mode.
Mirror the vertices of object 2 as if they were object 1. This causes the same problem.

Enlarge the Object-2 sideways.
Mirror the vertices of Object-2. The same problem still occurs. The problem occurs even if the Vertex-B x-coordinate is greater than 0.00002 after magnification.

X-Mirror_bug.blend
The objects in the X-Mirror_bug.blend file are very small, so zoom in on the view to the maximum size.

This is a 2.79b file with the X-Mirror working correctly:
X-Mirror_2.79b.blend

The difference in x-mirror behavior between 2.8x and 2.79b is shown in the following video:
Blender 2.8x BUG_X-Mirror.mp4

Blender 2.79b X-Mirror.mp4

If it is unintentionally aligned to the YZ plane like 2.8x, it will not be possible to edit it (if this behavior is a specification, it will be useful if you can implement it as a function separate from the mirror, align it to the YZ plane, and set a threshold to align).

When importing model data from the outside and editing a mirror, all vertices with an X coordinate of less than 0.00002 are already implicitly aligned to the YZ plane, so editing with an X mirror is no longer possible at all. Hence, until this bug is fixed, edits involving X mirrors should use 2.79b.

**System Information** Operating system: Windows-10-10.0.18362-SP0 64 Bits Graphics card: GeForce GTX TITAN X/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 431.60 **Blender Version** Broken: version: 2.83.3, branch: master, commit date: 2020-07-22 06:01, hash: `353e5bd749` Worked: 2.79b **Short description of error** Blender 2.8x has a bug that forces it to snap to the YZ plane with a value less than 0.00002. The above is occurring with the snap off. The bug occurs even if the vertex's X coordinate is moved to more than 0.00002. Duplicating the object does not eliminate the bug. **Exact steps for others to reproduce the error** 3D Viewport / Edit Mode. Create an object with the following vertices: ``` Object-1 = { Vertex-A x = 0.00002, y = 0.00005, z = 0.0 Vertex-a x = -0.00002, y = 0.00005, z = 0.0 Vertex-B x = 0.000019, y = -0.00005, z = 0.0 Vertex-b x = -0.000019, y = -0.00005, z = 0.0 } ``` 3D Viewport / Edit Mode / Tool / Options / Mirror X [enable]. 3D Viewport / Edit Mode / Snap [disable]. Select Vertex-A and Vertex-B. Move Vertex-A and Vertex-B. Blender 2.8x has a bug that forces it to snap to the YZ plane with a value less than 0.00002. 3D Viewport / Object Mode. Duplicate the Object-1 to obtain the Object-2. 3D Viewport / Edit Mode. Mirror the vertices of object 2 as if they were object 1. This causes the same problem. Enlarge the Object-2 sideways. Mirror the vertices of Object-2. The same problem still occurs. The problem occurs even if the Vertex-B x-coordinate is greater than 0.00002 after magnification. [X-Mirror_bug.blend](https://archive.blender.org/developer/F8716983/X-Mirror_bug.blend) The objects in the X-Mirror_bug.blend file are very small, so zoom in on the view to the maximum size. This is a 2.79b file with the X-Mirror working correctly: [X-Mirror_2.79b.blend](https://archive.blender.org/developer/F8717727/X-Mirror_2.79b.blend) The difference in x-mirror behavior between 2.8x and 2.79b is shown in the following video: [Blender 2.8x BUG_X-Mirror.mp4](https://archive.blender.org/developer/F8717729/Blender_2.8x_BUG_X-Mirror.mp4) [Blender 2.79b X-Mirror.mp4](https://archive.blender.org/developer/F8717733/Blender_2.79b_X-Mirror.mp4) If it is unintentionally aligned to the YZ plane like 2.8x, it will not be possible to edit it (if this behavior is a specification, it will be useful if you can implement it as a function separate from the mirror, align it to the YZ plane, and set a threshold to align). **When importing model data from the outside and editing a mirror, all vertices with an X coordinate of less than 0.00002 are already implicitly aligned to the YZ plane, so editing with an X mirror is no longer possible at all. Hence, until this bug is fixed, edits involving X mirrors should use 2.79b.**

p-tone commented

2020-07-24 02:06:21 +02:00

Added subscriber: @p-tone

p-tone commented

2020-07-24 02:10:58 +02:00

This comment was removed by @p-tone

*This comment was removed by @p-tone*

p-tone commented

2020-07-26 03:11:13 +02:00

2.79b seems to be forced to snap to the YZ plane at less than 0.00001.
It is still desirable to make selective snapping or not, and to make the snapping threshold optional.
If you want to do X-mirror processing and handle model data that includes vertices that should not be snapped to the YZ plane, if the original data to be imported is already in the snap range, the vertices will fall into a state where they cannot be edited arbitrarily.

Maybe it was originally intended to be placed at zero and is a specification to zero alignment when manipulating vertices, but it may be a factor that it's not designed for cases where you don't want to be placed at zero.

2.79b seems to be forced to snap to the YZ plane at less than 0.00001. It is still desirable to make selective snapping or not, and to make the snapping threshold optional. If you want to do X-mirror processing and handle model data that includes vertices that should not be snapped to the YZ plane, if the original data to be imported is already in the snap range, the vertices will fall into a state where they cannot be edited arbitrarily. Maybe it was originally intended to be placed at zero and is a specification to zero alignment when manipulating vertices, but it may be a factor that it's not designed for cases where you don't want to be placed at zero.

Germano Cavalcante commented

2020-07-28 16:00:00 +02:00

Added subscriber: @mano-wii

Germano Cavalcante commented

2020-07-28 16:00:00 +02:00

Changed status from 'Needs Triage' to: 'Needs User Info'

Germano Cavalcante commented

2020-07-28 16:00:00 +02:00

To detect the mirror elements, each mirror vertex must be within a threshold of 0.0002 considering the center of the mirrored vertex.
In 2.79 the threshold for mirror verts was different from the threshold for vertices that are close to the "mirror". If I'm not mistaken, this other threshold was 0.0001.
0.00002 is now used in both cases.

I'm not sure what this report proposes:

Lower the border threshold to 0.00001?
Keep the vertices "locked" to the mirror but do not set the coordinates to zero?
or something else?

To detect the mirror elements, each mirror vertex must be within a threshold of 0.0002 considering the center of the mirrored vertex. In 2.79 the threshold for mirror verts was different from the threshold for vertices that are close to the "mirror". If I'm not mistaken, this other threshold was 0.0001. 0.00002 is now used in both cases. I'm not sure what this report proposes: - Lower the border threshold to 0.00001? - Keep the vertices "locked" to the mirror but do not set the coordinates to zero? - or something else?

Campbell Barton commented

2020-07-30 14:10:34 +02:00

Changed status from 'Needs User Info' to: 'Confirmed'

Campbell Barton changed title from ~~Blender 2.8x has a bug that forces it to snap to the YZ plane with a value less than 0.00002.~~ to Mirror threshold too high, values less than 0.00002 are snapped to center

2020-07-30 14:12:34 +02:00

Philipp Oeser removed the

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Mirror threshold too high, values less than 0.00002 are snapped to center #79211