Animate IK evaluation-constraints?

#1

I am trying to evaluate the Ineverse Kinematic engine accuracy in the Messiah Animated 5.0 demo. I purchased, as part of a game development project, LW6 several years ago and the IK accuracy was so bad that the product was useless for our purposes.

I have been able to test some of the PM:A IK and it is much better, but I need to do further tests which I cannot figure out how to do.

I have set up a simple IK chain of two bones, with a null serving as an anchor, another as an effector, and a final one as a goal. It works fine, and is based on the biginning IK tutorial in the manual. From this meager setup, it is easy to show that the IK is much better than that in at least LW6.

But I need to constrain the bones so that they can only rotate on one axis, so that their motion is limited to only one plane. I tried to use the Clamp expression to do this, but I must be doing it wrong, because if I move the goal to the side (along the X axis), the bones follow.

Specifically, I want the bones to only be able to change their pitch, so that movement of the goal in the YZ plane should cause movement, bot movement on the X axis should not.

I am afraid I am an Uber-Newbie to this app- I downloaded the demo yesterday. Any help would be very much appreciated. If the IK looks good, and the SDK looks good, I am going to purchase a few licenses.

Best,
OwenDouglas

#2

It’s close to LW to do this.
Once the setup is done, and the IK too in the Animate menu, select your anchor point,
in he Inverse Cinematic tab, there is a button for “Minimum/Maximum”, just hightlight the buttons of the axis that you don’t want to rotate, and set Maximum:0 and Minimum:0
And here you go, that will rotate on one axis.

#3

Thank you very much for your reply. the technique you mention here works IF you want to constrain every bone in the chain, from the anchor down, in the same way. Which is good. But how do you restrict the joints of bones independently? For example, a hip can move in more directions than a knee joint, but they are in the same chain. If I set the min and max values for H and B to 0 for the anchor, all bones in the chain will only be able to move in the pitch direction. What if I want the hip to move in H and P, but not B, and I want the knee to move only in P?

I know there is an expression for knees particularly (kneeconstraint), but the IK chain above is just an example- I have no interest, yet, in making a leg, just checking out the IK.

Thanks!

#4

Look, I’m very new to this, so I may be completely off the mark here. But I just did a test, and if you crank your bone’s “stiffness” up to 1.0 in the IK block that essentially locks it from moving in that direction, right?

Robert

#5

Yup, that’s correct. An even better way to do it is to use the IKStiff expression so you can blend the amount of stiffness with a slider (or anything else for that matter) :thumbsup:

#6

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