v10 - Knee & Foot Target bone rig
Posted: Sun Mar 23, 2014 11:48 pm
This is a rig using the new v10 feature Bone Targets
v10-knee-foot-target-bone-rig
The simple and standard use of this bone feature for legs (and arms) would have one target bone for the foot and IK stretching set for the thigh and shin bones.
This works quite well and is simple to set up, however it does have some limitations. One of the issues is moving the knee or joint location. With the simple set up and one target for the foot the leg can only bend in one direction. To force the leg to bend in the opposite direction, you must force a rotation key on the shin bone. This works but causes the bend to "pop" instead of smoothly animate.
Another limitation is that both the thigh and shin bones will always scale the same amount to reach the foot target. In many situations this may be good enough, but doesn't allow for "foreshortening" or independent scaling of the thigh and shin bones for front walk cycles or perspective, when the shin bone is bent from a front view it would appear shorter.
Using this rig allows for independent movement of the knee. It allows for smooth changing of the leg bend direction with no "pop". The thigh and shin bones are scaled separately based on the knee and foot target bone location.
In addition to this, I've added two extra bones above the hip bone to control either the movement of both knees or both feet. Translating the body root bone will move the entire body except the feet target bones. The feet mover bone allows independent movement of only the feet.
A top level root bone allows for the entire character to be translated.
The Anime Studio file download is for v10 only. It includes two walk cycles using the same rig. A front walk cycle and a side walk cycle.
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Some "cheats" on the rig.
To get the results needed (this would apply to any target bone rig) I used bone offset for the target bones to "lengthen" both leg bones. The original bone set up has shorter legs so they can "stretch and squash". The IK Max Stretching for a bone only "stretches" it doesn't have "squash". To compensate for this I made the bones smaller or shorter than I needed. I then offset the target bones to where they should be to start. This allows for squash and stretch.
I could have done this by simply translating the target bones on frame 1, but by using bone offset it's sort of "built in" to the rig.
Of course this will require creating any vectors "pre squashed". Not a big deal in my opinion.
EDIT:
Same thing for image based characters. The legs (or arms) images would be created normally. When imported they would be "one way scaled" on frame zero to maintain the resolution. When the target bones are offset the image is "stretched" back to "normal" size.
v10-knee-foot-target-bone-rig
The simple and standard use of this bone feature for legs (and arms) would have one target bone for the foot and IK stretching set for the thigh and shin bones.
This works quite well and is simple to set up, however it does have some limitations. One of the issues is moving the knee or joint location. With the simple set up and one target for the foot the leg can only bend in one direction. To force the leg to bend in the opposite direction, you must force a rotation key on the shin bone. This works but causes the bend to "pop" instead of smoothly animate.
Another limitation is that both the thigh and shin bones will always scale the same amount to reach the foot target. In many situations this may be good enough, but doesn't allow for "foreshortening" or independent scaling of the thigh and shin bones for front walk cycles or perspective, when the shin bone is bent from a front view it would appear shorter.
Using this rig allows for independent movement of the knee. It allows for smooth changing of the leg bend direction with no "pop". The thigh and shin bones are scaled separately based on the knee and foot target bone location.
In addition to this, I've added two extra bones above the hip bone to control either the movement of both knees or both feet. Translating the body root bone will move the entire body except the feet target bones. The feet mover bone allows independent movement of only the feet.
A top level root bone allows for the entire character to be translated.
The Anime Studio file download is for v10 only. It includes two walk cycles using the same rig. A front walk cycle and a side walk cycle.
--------------
Some "cheats" on the rig.
To get the results needed (this would apply to any target bone rig) I used bone offset for the target bones to "lengthen" both leg bones. The original bone set up has shorter legs so they can "stretch and squash". The IK Max Stretching for a bone only "stretches" it doesn't have "squash". To compensate for this I made the bones smaller or shorter than I needed. I then offset the target bones to where they should be to start. This allows for squash and stretch.
I could have done this by simply translating the target bones on frame 1, but by using bone offset it's sort of "built in" to the rig.
Of course this will require creating any vectors "pre squashed". Not a big deal in my opinion.
EDIT:
Same thing for image based characters. The legs (or arms) images would be created normally. When imported they would be "one way scaled" on frame zero to maintain the resolution. When the target bones are offset the image is "stretched" back to "normal" size.
) It also shows how to animate the knee to avoid the pop (that was helpful to me, because of the issue heyvern mentions and the fact that the controls are not quite as intuitive for me when the target bones are involved).