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Broken Rotation to Deltas for Quaternions and Axis Angle
Open, Needs Triage by DeveloperPublic

Description

System Information
Operating system: Linux
Graphics card: -

Blender Version
Broken: 2.79b, 2.80, 2.81 Alpha 2019-08-26
Worked: -

Short description of the bug
Apply Transforms > Rotation to Deltas, does ADD the current rotation values to the existing delta transforms
For Quaternions that should MULTIPLY with the current delta value. Due to the fact that it adds it,
it results in a different transform after that operation.
Also Rotation to Deltas does entirely fail for Axis Angle rotation representation.

Exact steps for others to reproduce the error
Start with the default startup file and rotate the cube randomly.
Set the rotation representation to Quaternion or Axis Angle.
Press Ctrl+A and select Rotation to Deltas.
The Cube now has a messed up non unit quaternion in the transform deltas
or nothing changed at all for the axis-angle case.

Details

Type
Bug

Event Timeline

IMO, Not looks like a bug...
I think, Rotation To Deltas works just like this. as tool-tip saying:


Exact Steps:

  • Rotate Cube -> Z Axis -> 45d
  • Convert to Quaternion
  • Note values there (will be added with Rotation To Deltas):

  • Ctrl + A Apply -> Rotation To Deltas

Values are added up to existing transform (cube) & reset to defaults in text-fields

Before Applying:


After:


All Blender versions -> Same behavior
Thanks

As I understand the apply operators, they should all leave the visuals exactly as is, so this is a bug. It completly not doing anything with axis angle representation is a bug for sure though, but even the problem with the quaternion isn't, that it rotates the cube, the problem is, that the resulting delta quaternion is not a unit quaternion (which all rotation quaternions are unit quaternions)