Hierarchy & Deformers

Hierarchy

Today we covered hierarchies in Maya, in general and their use in animation.

The simplest way to review this is *starts humming*:

"Toe bone connected to the foot bone

Foot bone connected to the heel bone

Heel bone connected to the shin bone"

Along with the rest of the song ‘Dem Bones’.

While hierarchies are useful in most situations. Look at how much I’ve been using them in Unity to keep assets organised. In character animation their use really does boil down to singing ‘Dem Bones’ and allows us to organise which parts of the character are connected to other parts and ultimately what bits move when you move objects further up the hierarchy. Move a forearm and the hand moves with it etc.

Maya uses the same terminology as Unity. At the top of your stack you’ll have a parent and anything associated to this in hierarchy will become a child of that parent. Move the parent, the child moves. Move the child and its still free to move on its own.

Deformers

It’s hard to describe the general function of deformers without sounding obvious. In some way, shape or form they deform your mesh in smooth ways in ways that wouldn’t be possible or easy editing geometry. Mostly though they are for animating as you can keyframe the results. For example there is a squash deformer you can use to get exaggerated squash and stretch in your animation, this would have been a cleaner method of squashing my flour sack rather than animating a scale transform in the Y axis.

These are accessed from the Deform Menu > Non Linear

The cylinder above on the right has a bend deformer applied to it, you can see its controller down the middle of the cylinder if you look carefully. It has had no alterations made to its geometry at all, just the deformer.

The Task

We were assigned the task of creating a simple character rig we could use to teach ourselves how to setup hierarchy and potentially use in our future animations. The advice was to stay away from anything with legs and consider making a character out of inanimate objects, or a simple robot.

For anyone who has read my blog up till now, I picked a robot. No surprise.

The example given was EVE from WALL-E. No legs, very few moving parts. Simple construction.

3625885-4897998087-wall

I looked on google for similar other robots and found ONE example. Which seemed a little odd. This example was a hover robot, apparently from He-Man, a minion of Skeletor, I seriously don’t remember this from childhood. The other one I thought of myself was the robots Hack and Slash from the kids show Reboot (90s classic early CG).

I ended up more or less modelling the hover bot. It was one tapered cylinder with a fixed rotating head and two tube arms. It seemed perfect for the job. I just hope that’s acceptable for the exercise.

robot_currentprog

I ran out of time in class to model the arms with any detail so for now I just threw in a series of tubes to setup and demonstrate hierarchy. I spent too much time on the body.

hypergraph_hierarchy

As you can see in the hypergraph hierarchy editor the main body is the parent right at the top of the chain. Under this the direct children are the head and upper arms, the eyes and lower arms and hands are then further down the chain from these. Using middle mouse in the editor you can drag nodes onto others to start the parent/child relationship, you can also use Shift+P. While doing this I made sure to identify all objects and rename them for ease of use.

Backing up a little bit, before you begin any of this, make sure you delete all history on your objects, freeze transformations and set your pivot points on each object using snap to guides. Otherwise you’ll almost guaranteed run into issues further down the line.

snapto

So far the head rotating in place looks great however I really need to make a permanent solution for the arms for later use. Shouldn’t be too much of an issue to set a new hierarchy up with new objects, once you know what you’re doing its a quick process.

 

 

 

 

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