As you can see from this screen shot, I’ve been animating this rigged character, and for the life of me - I cannot figure out why all of a sudden it’s auto keying with constant keys (i think that’s what they are called) and I cannot give them handles to smooth out the curves.
What gives?
Have you tried selecting all bones & all keyframes in the graph editor and set the key interpolation to beizer?
Randy
Thank you. I tried that, and it appears that the key frames BEFORE the keys I was setting we’re set to a mode that had a handle only on one side. How do you think that happened? 
Hmmm… TBH, no idea on that one.
Can you upload the file? I’ll take a look at it.
Here’s a thought… In the graph editor’s menu, under channel, you’ll find extrapolation mode, try setting it to linear and see if you get the other set of handles back.
Honestly, I used to be really strong in the graph editor with f-curves & drivers, but I’ve been away from blender for a few years and I’m a bit rusty. My current version of blender is out-of-date, so some things I’m sure have changed since I’ve been away. So here’s my thinking, (and I maybe crazy), if the f-curves are set to constant extrapolation then the second set of handles, to the right of the current frame in your image, aren’t displayed because they would have no effect. In my out-of-date blender 2.74, I have the second set of handles and can adjust them, but they have no effect on the f-curves when set to constant extrapolation.
Hope this helps,
Randy
I don’t have your file, but I can recreate a one handled keyframe:
So this is viewed in Graph Editor with the right side menu - key N to see it.
You can do the same with a Constant keyframe:
Things which effect handles:
The number of handles on non-Bezier keyframes can be effected by what is on either side of the chosen keyframe.
Bezier keyframes must have two handles, but the right one will only be 1 unit away, if the next keyframe is not a Bezier, same applies to the left handle if the previous keyframe is non-Bezier.
You can scale keyframe handles, but if you scale them to 0 on a Bezier it will scale both handles to 0, but it is still Bezier type - odd I know but that is the case. The only way to get them back again is to set values in the boxes, as if you try to scale them they won’t move - any number multiplied by 0 is still 0.
In my last image, the keyframe before the one highlighted is Bezier, hence the constant keyframe has a left handle and the keyframe after is a linear, hence the highlighted one has no right handle. How your keyframes became a particular type, I don’t know, but the Graph Editor with the right menu is the way to cure the issue.
Following on from my last image, I have now changed the keyframe before the highlighted on to Linear, it has therefore lost its left handle as well, but remains a constant type:
I hope this clears things up, otherwise we need to see your file.
Cheers, Clock.
