0
$\begingroup$

This is not a request for help but more an observation that invites other observations related to it. It has to do with rotation animation in Blender.

Please note that in the following the object being animated is at the world center and has no scaling or rotation.

  1. Animating a "cube" seems very straightforward. Set keyframes at desired start and stop frames with 0 and at 360 rotation, respectively. Modify Graph Editor settings as needed. The cube rotates perfectly. Adding an "empty" in this case is superfluous.

  2. Animating a UV sphere, however, can get tricky. Following the same steps as above, the sphere does NOT rotate as one would expect. It appears to start rotating in the desired direction but then stops and begins rotating in the reverse direction. I broke it up into four different rotation steps but that did not help. The only thing that worked was to parent the sphere to an empty and animate the empty.

I even went so far as loading the "factory" defaults to make sure I had not altered something that would cause this. The same thing happens. The fact it can be worked around makes it a low priority thing but it raises a question for me.

Why doesn't the sphere behave exactly like the cube when animating? I assume the nature of the sphere's geometry is somehow involved but a cylinder animates correctly like the cube. Same with the monkey and the monkey is somewhat spherical topologically. So what is it about the UV sphere that makes it prone to this odd behavior?

As far as I can tell, it is only the UV sphere that is giving this odd result. I'm on Blender 2.75 (just released) but I recall running into this problem in previous versions of Blender although I don't recall the details now and I was able to find a workaround.

If anyone tries this, let me know if you see the same odd behavior I'm seeing. The sphere, animated to rotate about 360 in a given timespan appears to rotate in one direction then reverses and rotates in the opposite direction. I thought it might be the rotation itself was fooling my eyes but I watched the "Rotation" values during the animation and those values validate what I'm seeing.

Improve this question
$\endgroup$
5
  • 1
    $\begingroup$ How exactly are you animating it? The way I'm doing it is by typing 360 into the shape properties menu, then keyframing it with I. It works fine for every shape that I've tried. (This is meant to be a comment) $\endgroup$
    – Woofmao
    Commented Jul 3, 2015 at 17:51
  • $\begingroup$ This is because the rotation is local, and not global, i encountered the exact same problem in the game engine not to long ago. What i mean by local, is that as the sphere rotates, so does the axis that it is rotating upon. once it rotates a full 180 degrees, it wants to go the exact opposite direction. writing an answer for you in 3... 2... $\endgroup$
    – ruckus
    Commented Jul 3, 2015 at 20:17
  • $\begingroup$ that doesn't happen for me ! $\endgroup$
    – Chebhou
    Commented Jul 3, 2015 at 21:37
  • $\begingroup$ I tried changing the locality but that did not work. I used both approaches, typing the values in the Properties menu and physically rotating the sphere (just to see the effect). I consider this odd, then. Everything but a UV sphere animates properly when rotated, at least for me in the official 2.75 release. There has to be a reason -- this cannot be due to a graphics card issue. I repeated this earlier today and got the same result. Very, very weird. More research ... repeat: this only affects the UV Sphere, no other object that I can tell. $\endgroup$
    – prairiemain
    Commented Jul 4, 2015 at 13:57
  • $\begingroup$ It sounds like a gimbal lock problem. Set in your object tab of your sphere 'Rotation Mode' to 'Quaternion WXYZ' and delete the old keyframes and reanimate it. $\endgroup$
    – MrRabbit
    Commented Sep 20, 2015 at 15:32

0

Reset to default

You must log in to answer this question.

Browse other questions tagged .