Attaching at High Res Beard to a High Res Face
Rig Demo Showing Layers and Animation Example
There are several issues with connecting one high res mesh to another such as how the surface is being deformed, painting weights, and play back speed. The typical approach is using a Wrap deformer. Though this can work in some instances, it can be unbearable slow to work with, bloat the scene size or worst case straight up crash Maya.
Another option is to bind the beard to the same joints as the face. Again, this can work, but if the face is being driven by blendshapes, the beard would need the same shapes sculpted for it. This would increase the workload, playback and scene size.
High Res Face Mesh
Having tried the options above, I went with a more layered approach. First, I created a low res mesh based off the head mesh, and reduced it further to only where the beard connects. Since my face setup is a primarily joint based, but requires a blendshape to pipe in the face animation under the body weighting, I needed to create a duplicate of this reduced mesh. I bound the head reduced mesh to the body joints, and the facial reduced mesh to the facial joints. I think created a Front of Chain blendshape from the facial reduced mesh to the head reduced mesh.
Low Res Face Mesh
Once this setup was created, I used a rivet script (found here: http://www.creativecrash.com/maya/script/rivet-button ) to attach rivets along the head reduced mesh. I created about 120 rivets spaced fairly evenly over the surface.
Beard Rivet Locators created on Low Res Mesh
Once the rivets where created, I created a joint per rivet and parent constrained the joint to the rivet.
Joints Constrained to Rivets
After the joints are in place, I bound the beard mesh to the joints. The initial weights worked pretty well, but still a few strands required some weight clean up. You can learn more about painting weights on high res meshes here: http://www.3dfiggins.com/writeups/paintingWeights/
Beard Mesh Skinned to Joints
Lastly, to help playback even more, the beard mesh was grouped and the visibility of that group connected to a channel the animator can quickly turn on/off. This way they can work without the beard, flip it on, and playblast for review.
As a closing thought, though this process works well, depending on the length of the hair, another solution or additional setups may be required. You can see the hairs on the upper lip at the corner of the mouth start to stretch on the smile. Though this would likely not to be noticed during a fully animated scene, it may be called out. I believe had this been needed, I would go in and individual weight those hair strands to their base joint, and remove the weights from the neighboring joints.
Other Opinions, Further References, Typos, and Grammar Issues please contact KielFiggins22@gmail.com