Operating system: Windows-10-10.0.17763-SP0 64 Bits
Graphics card: GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 445.87
Broken: 2.57, 2.79, 2.80, master (rB7d2b4ae9c6ecce394130)
Worked: probably never, didn't test on Blender older than 2.57.
Given a chain of bones controlled by a Spline IK constraint, the first bone in the chain will scale to fit the spline curve. This happens even when Y Scale Mode is set to None.
Exact steps for others to reproduce the error
- Open the attached Blend file. This is set up to have Y Scale Mode: None.
- Move the Handle-End empty around.
- See that the first bone (the yellow one) scales. The red bone copies only the location+rotation to visualise the difference in scale.
Original blend file: