“CHARACTERS USING PROPS in CAT2.5” by Tom Mooney
This simple demonstration shows how to use Link Controllers and Helpers to make a convenient process which allows objects to follow the CAT bones and for IK controlled CAT bones to follow objects. It is a bit more complex than using direct links because it deals with cases where you want the objects to swap from hand to hand or to be picked up and discarded, or swapped out for different model versions. Level of difficulty: Only hard at first 🙂
Part 1: Preparation
Freeze or even hide parts of the scene that can get in the way of easily selecting the cat rig, such as the floor and the character mesh. You can sometimes even hide parts of the cat rig like the spine bones that aren’t commonly manipulated.
It can be a good idea to put these elements onto a seperate layer and hide/freeze it that way. Otherwise use the Right-Click, Properties panel.
Calling helpers ‘helpers’, points ‘points, and dummies ’dummies’ is good. Some 3D software has other names like nulls, but the point here is that it can be good to use points for one thing and dummies for another. I use points to link something to the cat node and dummies for things I’ll actually animate. Don’t forget you can use anything as a helper and filter helpers using layers instead of the old hide helpers display setting. It’s a good idea to be systematic because when you have lots of helpers, identifying them is crucial. Naming also helps. I use a prefix and then give each one a name.
Part 2: The CAT rig and the link controller
The link controller is the easiest way to deal with bindings of props. It’s not a good idea to use direct linking because that’s only for permanent links. The controller lets you swap bindings from one thing to another.The problem is you can’t join objects directly to CAT rigs using the controller (because uses its own type of controller system). Therefore, an intermediate helper is used to do the work of binding.
The correct linking hierarchy for a spear carried by the hand, where the spear could be thrown or passed from hand to hand, is as follows:
Spear (link to) Spear Dummy [Link Controller] Point_Hand (link to) Rig Palm
That’s very easy, but there’s a bit more to it than that, to make it work really well, and mostly that’s to do with keying the passover of the object, and a couple of extra steps for two-handed items or usage of IK.
Part 3: Alignment
It’s a good idea if there is an orderly relationship of pivot points to the linked objects and bones in your scene. A spear should have one axis parallel with its length for example. It’s good if the binding object can align perfectly with the helpers involved. This will help to get predictable results.
The Spear and its Dummy have the same axis. It can help too if they are in the exact same space.
Likewise, the palm bones and their point helpers share a common axis alignment.
In CAT bones the Z axis points along the bone length, so it can be a good idea to make the Z axis align with the spear length instead of X, but that’s not that big a deal.
Part 4: Process
Starting point
Final Goal
In this example the spear is in the ground, and the character moves to pick the spear up.
Part 5: Creating the helpers
The first helper is a dummy which is directly linked to the spear. While it’s possible to act on the spear itself, usually it’s better to apply controllers to helpers and have the geometry free so it can be swapped out for other models if need be, and if that happens the controllers are all okay because they’re on the helper. I’ve used a dummy because this is a helper I’ll be manipulating for animation transforms.
When you throw the spear, the animation will be on here.
On the palms we need a point helper which is aligned and directly linked to the palm. This is never animated itself, having the sole function of following the palm wherever it moves or rotates. Call it something like point_RPalm or point_RHand. CAT calls hands PALM for some reason, but you can actually change that by modifying the rig preset to be more like motionbuilder in naming. Anyway … link it up.
Pages: 1 2
Latest Comments