I’m new of Blender but I’m learning fast. For modelling etc. everything is quite ok… a lot of informations can be found online and usually are quite small stuff such as a shortcut etc.
My problem comes with the rigging of an animal’s leg. As long as I work with “humans” everything is ok. But animals have something different… while humans have a knee, animals have the leg that bends in two points [knee and heel].
While for humans you setup the IK chain from the heel for an animal I setup it from the paw [animals walk with the knee “high”]. But if I set up the IK chain from here I have two problems:
I can create a target just for the first bone that is part of the IK chain [in this case the one that goes from the paw to the heel] but not for the knee. This means that if I stretch the leg and then I compress it again I risk to bend the knee on the other side.
The IK chain works great with two bones, but if I add a third one the second and the third appear like “fused together” and the knee remains blocked.
Is there a way to sort this out? Probably is me that still ignore some stuff but I’m keeping this project as something that I can use to improve…
Ok, you need two pole targets, one to keep the heel pointing in the right direction, the other to keep the knee pointing in the right direction. They could even be the same bone, since the animals leg would probably stay lined up, you could use the same target, just with the opposite pole angle.
However, an IK constraint only gives you one pole target, so you’ll need two IK constraints. Try this: set up an IK constraint on the middle bone, length 2, with the bottom bone as target. Use the pole target to keep the joint pointing forward. Then set up an IK constraint on the bottom bone, length 1, with the IK bone as target.
Use the same pole target (Tailone) but use a pole angle to make the joint point backwards.
Now, the IK bone only moves bottom bone, but bottom bone moves middle and upper bone. You might have to remove some parenting between these bones to avoid circular dependancies. If the bones seem to go crazy when you try to pose them, you probably have a circular dependancy (one bone moves a second bone which in turn moves the first bone whiich moves the second bone, and on and on…)
Also, when you have the time, take a look at 'Humane Rigging’by Norman Vegdhal.
