trouble with knees and elbows

my character rig seems ok on the first frame, but when i try to add key frames the ik messes up and the legs end up backwards. Any help would be valuable.

Also on one of my rigs the ik chains lose there targets after i move off the first frame and all target the same object,(the last target i used). Im not sure if the two probles have a common root.


Blender bones have shortcomings, first you cannot constraint rotations (yet) so unless you pay particular attention in rigging it is easy to get knees and elbows go wild.

Read the manual… it is online


will rotation contraints be out in the next release?

I heard it is a high priority target.


Iv read the character animation section on the docs.
I have also downloaded a couple of free rigs as a result of advice from other forum questions(thanks guys), but Im still missing something.
I could just try to get permision from the people that made the rigs and use those, but I prefer to fully understand a rig im working with.

I know that stabalising the knees and elbows is possible as the rigs
I downloaded have working targets for both.

I am using cubes as my Ik targets intead of bones as this is closer to the
max way I origionally learned,Could this be cousing the prblem?

for now. you can constraint the ik chain from going the other side by adding a ik solver in the middle of the chain, and adding a bone on the side you want your chain to go.
here it is explained under “ik constraint”

Thanks for the tip, managed to construct a good stable rig with the knee
target, but for some reason the const box in the ik constraint turned red.

This was ok but when I tried it with a foot rig from the blender docs
the copy location constraints also turned red and this time stopped working.

Do I need to mess with the tolerence or influence on the ik constraints at all?, or is it ok just to use them as is?

red usually means you have a loop in constraints somewhere. make sure your target isn’t tracking something else thats being affected by your object.

make sure theyou parented your bone under the solver in the chain. see the blend file for example.

well i deleted my copy location constraints,these were cuasing the problem.
And just parented the objects.
So now iv got a pretty good foot rig joined to a fairly stable leg with knee target.
Would nulls be usefull in getting the copy locating to work?