Finally I arrive at the polish stage of my strut cycle. Because I had been quite detailed with the previous steps, there was not alot to do here. I still had some problems with knee-wobble which my teacher helped me diagnose. It turned out that the center of gravity was sitting a fraction too far back, so translating Z slightly forward partly solved that issue.
The other contributor to the knee wobble was that the ball roll on the feet needed to happen slightly earlier in time. Shifting those keys from frame 9 to frame 6 (and the reverse) helped to avoid ever having the knee ‘lock out’ in a fully straight position.
I am still being amazed by simple timing changes and how well they can fix things if you get an eye for diagnosing the problems.
So with everything happening much smoother, the last thing to do was to to get the global control moving in Z and taking him forward. You could refer to this process as taking him off the treadmill 🙂
Maths can be used effectively for this. The essence is to find the total distance that the foot travels in a complete step. This can be done by adding the z translate value for the rear of the contact position and adding it to the z translate value in the front of the contact position. This tells you how much you will need to move the global control in Z to match the forward momentum. So once you have that value, you can key the global Z translate at frame 12, make the tangents linear and cycle with offsets. This is the first step in getting the foot to not slide when it is in contact with the ground.
The other important step is to make sure that during the ‘contact’ period, the foot translates in Z in a very linear way (no easing in or out). That way the backward motion of the foot will ‘cancel out’ the forward motion of the global control which is moving in a perfectly linear tangent.
The foot can have an arced shaped Z translate tangent while in the air, but when in contact with the ground it must be linear to truly not slide.
Anyway, I learned on lot on this little project, here he is in all his glory. Remember to sing ‘stayin’ alive’ while viewing this –
and here he is from the back so you can check out his sweet booty!