When the object rotates quickly in a short number of frames, the blender does not understand which direction it needs to rotate

Question

[this has been asked by a new user Павел Семенов and consequently deleted, but since I had an answer ready I'm reposting it - MVB]

STEPS TO REPRODUCE

1. Open default "cube" project
2. Insert rotation keyframe for cube at 0
3. Move keyframe to 150
4. Change rotation of the cube to 7200 degrees (20 spins)
5. Insert keyframe at 150
6. Run animation and observe the direction of spining of the cube

EXPECTED RESULT

Cube spins in one direction

ACTUAL RESULT

Cube spins in diferent directions

ADDITIONAL INFO

After changing same keyframe from 150 to e.g 350 (expanding the lenth of animation), no issue appears

How to solve this?

Answer 1

As in Gordon Brinkmann's comment [now inaccessible due to mentioned deletion]:

I'm sorry, but this is simply wrong, the cube is not spinning in different directions - it is an optical illusion. Try searching "wheel spinning backwards illusion" on Google or Youtube. What you see with the cube is a similar effect. Maybe you also have the animation on Bézier interpolation instead of Linear? The changing speed creates the effect of changing directions. With a Linear interpolation the direction would probably seem to be always the same (even if it would look as if it was going backwards, it would be constantly going backwards).

As for your question:

How to solve this?

Enable motion blur:

Other than slowing the object down you can also remove its radial symmetry - the cube looks the same after being rotated by a(n integer multiplier of) 90°, so I extruded it to a side to remove that symmetry: