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As we get into rigging and making our character move, once we've added these IK constraints onto these bones, Blender will attempt to orient the bones anyway that it can in order to solve this problem of how to meet the target. If it gets out of range, then the bones is kind of snap out and it's just like you can't quite reach it. So that also means though that as we comek over here, let's say to the side view, it means that if this IK target happens to get behind it, you would be able to actually reach around and look his elbow or something like that and that's just not physically possible and it won't look real.
So Blender provides the option to limit the rotation of these bones in the IK chain. So here I've set up a standard kind of a limit for the elbow. The elbow is a hinge joint. He can't twist his elbow. The elbow can only go 1 axis and that's actually the X-axis here. So as I'm moving my IK up and down, you'll notice that the elbow just rolls along the X-axis.
And that translates into a very realistic motion when we add and enable the mesh by Shift-clicking Layer 2 here. Now as he punches forward and he is going to punch out ignorance or something like that, as his arm comes back, the elbow looks like a real elbow. And it's not twisting or turning or doing anything funky like that. And the way we set that up is in the Armature Bones panel, for a bone that's within an IK chain you'll have these limitations and locking mechanisms that appear down here.
And what we've done is we've limited the X rotation from anywhere from -100 degrees to a max of 70 degrees. And what I'm going to do is I'm just going to drag here and you can see the red axis because RGB, XYZ, the red arc, indicates the range of motion that this bone is able to take and as I restrict down this range of motion you can see the arc getting smaller.
I have locked the Y-rotation and the Z- rotation. I could go ahead and just lock the Y-rotation, and now when I click Limit Z, because Z is a full circle, Blender draws this sort of envelope that shows all of the possible places that this bone could point to. It's kind of a surface, kind of a mesh, or nylon mesh kind of a thing. And that tells you that for this bone to be in this position then these are the possible positions for this child bone further on down the road.
And allows you to visually see where this guy is able to reach. In this case let's say we want to knock it down a little bit. If we go ahead and set them, minimum Z to let's say minus -100 degrees, he'd actually be able to twist his elbow and sort of a kind of a shoulder kind of a mechanism to be able to get to any of these other positions as well. Actually when we do the shoulder bone, we'll do the X and the Z as well. But for the elbow and for the knee, just disabling the limit and locking the X is the proper way to go.
And then we're going to reset this back up to the way it was at the beginning. And that gives a fairly realistic range of motion and that's the way you set up range of motion in Blender, so that the IK solver can provide realistic solutions.
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