Hey forum,
I've maked a bodyturn. If I turn the character to the left all works fine with the legs.
If I turn the character to the right and lift the traget bone of the foot the knee rotates in the wrong direction.
How can I prevent this?
Bodyturn - Legs rotating in the wrong direction
Moderators: Víctor Paredes, Belgarath, slowtiger
Re: Bodyturn - Legs rotating in the wrong direction
It would help if you post a pic of exactly what's happening, but I'll try to make a couple of guesses.
The error is quite possibly a combination of these two.
If the lower leg is bending the knee in the wrong direction, you need to change the 'preferred' IK direction. To do this, select the Transform Bone tool, select the lower leg bone, and slowly drag 'rotate' it in the direction that the leg is currently bending towards (that might seem counter-intuitive but it's correct.) At some point, knee should pop into the opposite direction. As in the above, you'll probably want to keyframe the rotation in the frame before the flip. If the animation is slow, you may also need to finesse the transition by repositioning the body's hip/root bone or the leg bone lengths. Or, just speed up the animation to where nobody will notice the pop.
If the leg artwork and bones have flipped correctly, and you're using a target for the ankle, and you probably have Independent Angle enabled on the foot, the foot is not going to flip 'correctly' because of the Independent Angle. You'll need to manually rotate the foot to correct this. Just remember to keyframe the foot rotation in the frame before the frame where the flip occurs.
The first point should address what you've described but if you used a typical leg setup, the second point will probably also need to be addressed.
These are not bugs, btw. It's just how it works. I sometimes have to take similar actions even when working in certain 3D animation programs.
Hope this helps. If the above doesn't apply, please post more info and pics if possible.
The error is quite possibly a combination of these two.
If the lower leg is bending the knee in the wrong direction, you need to change the 'preferred' IK direction. To do this, select the Transform Bone tool, select the lower leg bone, and slowly drag 'rotate' it in the direction that the leg is currently bending towards (that might seem counter-intuitive but it's correct.) At some point, knee should pop into the opposite direction. As in the above, you'll probably want to keyframe the rotation in the frame before the flip. If the animation is slow, you may also need to finesse the transition by repositioning the body's hip/root bone or the leg bone lengths. Or, just speed up the animation to where nobody will notice the pop.
If the leg artwork and bones have flipped correctly, and you're using a target for the ankle, and you probably have Independent Angle enabled on the foot, the foot is not going to flip 'correctly' because of the Independent Angle. You'll need to manually rotate the foot to correct this. Just remember to keyframe the foot rotation in the frame before the frame where the flip occurs.
The first point should address what you've described but if you used a typical leg setup, the second point will probably also need to be addressed.
These are not bugs, btw. It's just how it works. I sometimes have to take similar actions even when working in certain 3D animation programs.
Hope this helps. If the above doesn't apply, please post more info and pics if possible.
D.R. Greenlaw
Artist/Partner - Little Green Dog | Little Green Dog Channel on Vimeo | Greenlaw's Demo Reel 2020 Edtion
Artist/Partner - Little Green Dog | Little Green Dog Channel on Vimeo | Greenlaw's Demo Reel 2020 Edtion
Re: Bodyturn - Legs rotating in the wrong direction
BTW, most of the time I won't bother putting leg flips inside a body turn SBD Action because I often find that during animation, I may actually want the leg to flip sooner or later than what the Action pre-determines for the rig, or I may possibly not want the leg to flip at all.
Instead, I'll create separate leg turn SBD controls that I can use when I want to turn the legs, and use them to turn the legs as far as I need to, independently of the body turn SBD. This setup can offer a wider range of posing possibilities than what a single 'do it all' body turn SBD might do.
Just something to think about.
Instead, I'll create separate leg turn SBD controls that I can use when I want to turn the legs, and use them to turn the legs as far as I need to, independently of the body turn SBD. This setup can offer a wider range of posing possibilities than what a single 'do it all' body turn SBD might do.
Just something to think about.
Last edited by Greenlaw on Mon Apr 17, 2017 11:09 pm, edited 2 times in total.
D.R. Greenlaw
Artist/Partner - Little Green Dog | Little Green Dog Channel on Vimeo | Greenlaw's Demo Reel 2020 Edtion
Artist/Partner - Little Green Dog | Little Green Dog Channel on Vimeo | Greenlaw's Demo Reel 2020 Edtion
Re: Bodyturn - Legs rotating in the wrong direction
Wow, thanks a lot for your detailed answer. 
Re: Bodyturn - Legs rotating in the wrong direction
Oh no,
I'm a little bit confused. The leg flips but I don't know how I maked this. There's no keyframe.
Could you explain this easily for me please?
Thanks a lot.
View My Video
I'm a little bit confused. The leg flips but I don't know how I maked this. There's no keyframe.
Could you explain this easily for me please?
Thanks a lot.
View My Video
Re: Bodyturn - Legs rotating in the wrong direction
Here's my problem: If I turn the body to the right the angle of the leg is ok. If I turn the body to the left the angle should turn.
But that doesn't work. So, what should I do to change the angle of the knee when I move the target bone or the smart bone of the body?
But that doesn't work. So, what should I do to change the angle of the knee when I move the target bone or the smart bone of the body?
Re: Bodyturn - Legs rotating in the wrong direction
You need to change the preferred IK direction when the leg rig flips. The preferred IK direction can be influenced by a small bend in the joint. You can that by changing the bend direction.
To do this while using Target bones, select the Transform Bone tool, then click on lower leg bone and drag it in the direction the knee is pointing. The knee will change direction when you've crossed the IK threshold. When you're using a target bone, the knee should eventually 'pop' in the opposite direction.
Be sure to keyframe the rotation angle of the leg bone in the frame before the flip, otherwise, the preferred IK direction may be affected for the preceding frames.
Optional suggestion: The sudden 'pop' is fine for very snappy animations, but for slower, smoother motions, you'll probably want to make gradual changes in the hip position and/or leg bone lengths, as described in the earlier post.
To do this while using Target bones, select the Transform Bone tool, then click on lower leg bone and drag it in the direction the knee is pointing. The knee will change direction when you've crossed the IK threshold. When you're using a target bone, the knee should eventually 'pop' in the opposite direction.
Be sure to keyframe the rotation angle of the leg bone in the frame before the flip, otherwise, the preferred IK direction may be affected for the preceding frames.
Optional suggestion: The sudden 'pop' is fine for very snappy animations, but for slower, smoother motions, you'll probably want to make gradual changes in the hip position and/or leg bone lengths, as described in the earlier post.
Last edited by Greenlaw on Tue Apr 18, 2017 10:21 pm, edited 1 time in total.
D.R. Greenlaw
Artist/Partner - Little Green Dog | Little Green Dog Channel on Vimeo | Greenlaw's Demo Reel 2020 Edtion
Artist/Partner - Little Green Dog | Little Green Dog Channel on Vimeo | Greenlaw's Demo Reel 2020 Edtion
Re: Bodyturn - Legs rotating in the wrong direction
Hello Greenlaw,
thank you for your anwser. I've made a mistake all the time: I've moved the anker (start) point of the lower leg bone instead of only select it and move outside of the bone.
Intuitive I've searched a point or a switch in the bone tools to change the IK direction. The solution is too easy to maked it right 
SmithMicro should install a switch for this 
Here is a video tutorial that makes it clearly:
https://www.youtube.com/watch?v=Utvx0zOzIWI
Puuh, a long way. Now, it works
thank you for your anwser. I've made a mistake all the time: I've moved the anker (start) point of the lower leg bone instead of only select it and move outside of the bone.
Intuitive I've searched a point or a switch in the bone tools to change the IK direction. The solution is too easy to maked it right SmithMicro should install a switch for this Here is a video tutorial that makes it clearly:
https://www.youtube.com/watch?v=Utvx0zOzIWI
Puuh, a long way. Now, it works