View Full Version : Using IK to make spider walk

02-14-2015, 11:22 AM
First let me thank everyone who has given me advice. Much Appreciated. All of you really help. Now on to my question. I'm really starting to focus on the animation part of lightwave especially IK. I'm doing an animation with the spider from the 60's version of Johnny Quest. It's a simple ball with and in the center and 4 cylindrical legs that grow out of the ball and have two joints. Check pic. I've got an IK chain on one leg. It bends correctly. What I need to happen is when the legs grow out and bend and hit the ground they need to cause the orb to lift off the ground and then the legs need to walk towards the camera moving the body.
1.I can't get the legs to raise the body or move the body when walking. What am I missing?(I'll be cloning the one leg with IK chain three times and moving them in place and I have a background with floor it'll be animated on)
2.What exactly is IK? What I mean is it an antagonistic relationship between items(bones)…setting up items to interact in a specific way on a plane by setting up a goal that when moved causes an interaction?
3.Do I animate the goal of each leg going forward up and down and keyframe the body separately? Or do I use nulls? Or should I get rid of IK and just keyframe the whole thing?
Thanks guys

02-14-2015, 04:22 PM
To get the body to rise up you need the key the position of the body. The body won't on its own move against the planting of the leg due to action/reaction.

IK is short for inverse kinematics. As an example, think of how you move your arm. Forward kinematics would be you rotating your shoulder, then elbow to pose your arm. The inverse of that would be someone posing your arm by grabbing your wrist and the rest of your arm follows, kinda like shaking your hand.

So for your robot the inverse kinematics goal would be the point where your chain ends, which I'm assuming is the tip of your leg. Ik is good for legs because you can move the body and the legs will stay planted since their posing is dictated by the ik goal and the rotation settings of each part. RebelHill has a good set of videos explaining inverse kinematics.

02-14-2015, 07:29 PM