|Facial Rig Setup Tutorial|
|A characters face can hold just as much expression as the entire body, so it is certainly important to make sure your facial rig meets all the criteria needed by the animator. Indeed there are many ways of going about setting a facial rig up, and here i will show the process of a way i find quite efficient.|
|This rig setup has the benefits of skin sliding throughout the face, meaning that whichever object you move, the rest of the face will be altered slightly, which helps prevent the static effect. It is also non dependant on full shape animation on the face, making it easy to add facial poses later along the production pipeline if needed (though i would advise whichever method you use, shape animation should always be coupled with it, and to always plan ahead what facial poses you will need ).|
So to begin with we need to start by mapping our deformation curves along the face, its important to note that these curves should follow the areas of the face that are driven by the muscle, as the curve will be where the movement is initially dirven from. For this tutorial, i drew my curve starting from above the nose, along the eyebrow, following around the eye to the upper cheak bone, following along side the mouth then looping aroud the chin.
A second curve is then used for the mouth, as well as two more curves for the eyes.
A quick tip for drawing your curves, enable snap mode, so it autmatically places the points where the points on the mesh are.
Once we have the curves drawn out, we should create a null, then path constrain this null to the main curve and activate the tangent, once constrained, duplicate it, and increase the path%, continually doing that until the nulls follow the entire curve. I chose to duplicate the nulls with an increment of 5 on the main curve.
Again we do the same method for both the eyes and mouth, for the mouth, i used increments of 10 then tweaked to get the nulls in the correct positions for deformation, and the same for the eyes only using a larger increment.
|So now you should have four curves in total, all with nulls path constrained to them. We will now move onto creating the main head bone, so we will use a two bone chain, setup as shown on the picture to the left, and then create another bone, which will follow the jaw line. The root of this jawbone should be a child of the first head bone as this will allow the jaw to follow the head.|
|The next stage involves creating clusters with centers from our curves, so select the curve, and select each point indivually, and each time choose "create cluster with center" you will notice that it generates a null at the point, and if you translate the null then the curve will deform with it which in turn effects all the nulls that are constraind to the curve, from this you should grasp how this will work to stretch the skin|
|We dont really want to animate straight on these nulls, mainly because there simply messy, and make it harder for the animator to see whats going on, instead, a more suiting object would be an implicit cube or such, but before we can do that, we need to break the parent relationship between the nulls and the curve, so select all the nulls that were just generated, and cut the parenting.|
|Now create an implicit cube, and enable snapping to nulls, and snap an implicit ccube to each of the control nulls. Then each cube that was snapped to a null wants to be the parent of the null it was snapped to. Making it possible to manipulate the curve by translating the implicit cube.|
|For the jaw to work correctly we need to parent the bottom control objects that are around the jaw to the jaw bone effector. So select the jaw bone effector, and choose "constrain / parent " then select the relavant ctrl objects that follow the jaw, now you should find that when you move the jaw effector in the Y position, the mouth will open, and the curve will deform. The rest of the ctrl objects should be made children of the main head bone.|
Once we have got this far you will see that there is now quite a lot of objects within the facial rig, so we should organise these into layers, making it easy to make certain objects visible or not. I chose to create a seperate layer for the following object types:
|Now our scene is better organised we can start to think about enveloping, so make only the geometry and deformer layers visible, and with the geometry selected choose, "envelope / set envelope " hide the geometry layer and select all the deformers. Right click to confirm.|
|I found that i did not need to alter the enveloping to much, though the main areas were as follows, the forehead (so the entire skull doesnt lift when you raise the eyebrows), the nose (so the nose doesnt completely move when you alter the jaw or forehead) and the lips, just because there normally modelled quite close to each other so the point wieghting will need adjusting.|
The main rig is now complete and could be animated on. I would advise to create transform saves of the implicit cubes to allow for use in the animation mixer, and ultimatly giving the ability of slider driven facial animation, which the animator will most likely be familiar with.