You can create an Anim Blueprint with a Two-Bone IK node for the arm/hand. It takes two inputs: an “Effector” location, and a “Joint Target” location. The “Effector” location is where the hand joint will go, so plug in an appropriate location vector (i.e., on the underside of the rifle) to make that work. The “Joint Target” location is essentially the pole vector locator, so use that to modify the angle of the arm. You might have to tweak the transforms further (e.g., the hand rotation), which you can do with a Transform (Modify) Bone node after the Two-Bone IK.
If you don’t know how to set up an IK limb rig in Maya, try Googling “maya ik arm” or “maya rotate-plane ik” or similar. Or better yet, watch a good rigging tutorial - there are a lot of resources out there and this isn’t a great place to get that kind of info. (For limbs, you typically want a rotate-plane solver with a pole vector constraint on it.)
I am new to Maya but I have been learning about IK and FK rigging, so I will take your advice.
I could still use some clarification. It makes sense what you are saying about the blueprint nodes, that they need a target location and the joint to move to that target, but what I am still confused on, is the “IK limb rig”, is that an additional rig that I put onto my base skeleton attached to the root, OR is it a completely separate rig that I animate along with my character and keep it positioned at the hand location during posing(i.e. I would import them as two completely different rigs into UE4)?
If it is supposed to be attached to the characters skeleton, how is it not influenced by the resizing / reshaping that the skeleton also goes through?
Again, thank you for your help. What you said makes sense, but I am having trouble with the implementation of the rigging setup. The blueprint nodes are pretty straight forward as you explained.
I see the UE4 Mannequin crouched down, but there is still that hand positioning IK rig in position. Is that attached to the root of the UE4 Mannequin? If so, how is it not affected when the skeleton of the UE4 Mannequin is resized?
Also, I have an IK and FK rig on my character currently in Maya and have been using it for animation, but can that IK and FK rig be imported into UE4?
I’m not sure of the question but are you confusing “joints” or “bones” with “rigs”? You could add joints (in Maya) with the root as parents that you use as IK effector targets in UE4, which is what the UE4 Mannequin does. They would just be part of your main skeleton, not a separate skeleton. I have done this and it works well.
Setting the retargeting to “Skeleton” or “Animation” will determine whether or not it follows the skeleton’s “base” locations or the locations specified by animation. Usually you want to set IK control targets to “Animation” so that they don’t move to a different place when the animation is applied to a skeleton with different proportions from the original. For different skeletons, you just can just exclude those joints from the retargeting instead.
It’s possible, but I think it would not be a great idea. I am not sure why you would want to import FK controls at all if you’re importing animations, since the keys are essentially just FK transforms. For limb IK you can just add Two-Bone IKs to your anim BP and turn them on/off using the Alpha property. They work pretty similarly to Maya’s rotate-plane IK (stretchy limbs would be harder). If you have in-line twist joints on your limbs, that doesn’t work directly, so it could be a good idea to import the IK joints in that case - it’s messy but I’ve gotten it to work.
You could also check out the Allright Rig to potentially rig and animate directly in UE4, but it costs $$$.
