Subdivison Surface modifier distorts shape keys

Hai,

I have the following problem. I would like to use animated shape keys to adjust my mesh in extreme poses (to avoid making for example an extremly bent knee look weird). So far so good, however, when I then add a Subdivison Surface modifier to it all, it absolutely wrecks the shape key modifications. Here is a comparison of what I mean:

With shape key and no Sub-D:

With shape key and Sub-D activated. Note how the knee goes ballistic:

Whats weird is that the model Im working with (which is a model based on a makehuman generated mesh) still has shape keys from the makehuman rig (mainly facial animations) that do not get distorted by the subdivison surface modifier, so there must be a way of fixing this, right?

Please note that im not talking about applying the modifier, as I know thats not possible when you have shape keys. I just want to use it in an unapplied state.

Help would be greatly appreciated with this, as I find shape keys can be an effective method of making rather simple rigs still look good in extreme poses.

Looking forward to replies!

Edit:
Alright, heres the file as requested. Shape Keys are set to 1.0 already (the shape keys in question are “CorrectiveKneeR” and “CorrectiveKneeL”, though this problem occurs for me with all shape keys that I add to this model, to varying degrees of extremity). All you have to do to observe the effect for yourself is put the “Subdivison Surface” modifier to 1.

It goes without saying, but please do not use this model in your own projects or anything (though why would you, lol):
https://www.sendspace.com/file/g7jz8e

Please supply a demo blend file for review

Alright, heres the file as requested. Shape Keys are set to 1.0 already (the shape keys in question are “CorrectiveKneeR” and “CorrectiveKneeL”, though this problem occurs for me with all shape keys that I add to this model, to varying degrees of extremity. All you have to do to observe the effect for yourself is put the “Subdivison Surface” modifier to 1.

It goes without saying, but please do not use this model in your own projects or anything (though why would you, lol):
https://www.sendspace.com/file/g7jz8e

Edit: W00ps, double post, sorry.

Check CorrectiveKneeR and CorrectiveKneeL shape keys in edit mode. That is your prob with the mesh. Fix this and it should work fine.

Wonder if you are going to animate this. I see the feet might give you problems in the future if you are. An easier method to rig this is to have the IK bone in the same position and rotation as the foot bone in edit mode. Then add copy rotation constraints to the foot bone from the foot IK. This allows you to rotate the foot and the IK at the same time without editing manually editing both separately. I recommend also finding a Heel and Toe rig tutorial. Vscorpian’s foot rig tutorials in youtube may help you. Heel and toe rolls will be a strain to do manually.

Great, thanks for the answer! Ill try it out as soon as Im back working on fixing the model (currently working on a different part of this movie). However, do you have any idea how to setup shape keys that dont do this? Like, why is it screwed up in edit mode like that?

And yes, I am going to animate it. I know the rig isnt ideal, however I will get into more complex rigging with later characters of mine, for this one the huge time investment of a super rig isnt quite realisitic. Im used to animating much worse rigs so the few IK parts in it are already a huge help for me.

Alright, Ive figured it out. Im an idiot. Keep your modifier orders straight, guys.

Heres the deal: When using sculpting tools to make shape key modifications and you afterwards want to use a Sub-D modifier, make sure the Sub-D modifier is at the very bottom of the modifier stack or else the shape key modifications that were applied using sculpting will go ballistic. Atleast they did for me. Solved I guess, awesome.