Hi,
when using human rig with Rigify (blender 2.78c), the feet won’t stick to their position, making the knees bend when I lower the body, box control. Both legs go through the floor, knees unbent. Also cannot move feet forward/backward. Any idea why this is?
You need to switch the Rig to “IK” mode and anchor the feet IK targets - they should be parented to the “root” bone so should not move anyway. The Rigify rig is in “FK” mode by default, this is so you move the thighs, lower legs, etc. rather than moving the hands or feet to where you want them and the legs/arms will then bend as appropriate. it also applies that if you move the torso, in IK mode the feet will stay still and the legs will bend.
Then you make sure you have the RH Menu (key N if you don’t see it) Go down to Properties and set “ikfk_switch” to 1 for IK mode and 0 for FK mode. You only see this if you have selected an IK target bone…