Group Based Foot vs Reverse Foot

Here are two common foot control set ups compared and contrasted. We will start with the group based foot set up, then examine the reverse foot control.

With an easy set up, the group based foot control helps keep the skeleton clean by not using unnecessary joints. By grouping the IK handles under null group nodes, the group nodes pivots can then be placed anywhere and influence the joints rotations.

This setup is easily completed using the Hypergraph to select and group the proper nodes.

Here is the proper layout in the hypergraph, post-completion of the group based foot control. It’s important to pay attention to the grouping or the bones rotations will be screwed up. Name everything properly and pay mind the rotation axis that you are keying in the set driven key editor. I am personally a big fan of the ability to use the “Toe Twist” attribute, which really makes the foot appear planted while the heel is able to rotate in the Y axis.

*Note the error in The Art of Rigging (TAR) on page 25, where they say to key the RotateX under the heelPivotGrp and toePivotGrp, in the table on the right column — to accomplish the proper control you must key the RotateY!!! Check it out below.

An inverse foot control locks the joints of the foot (ankle, ball, toe) to a reverse lock joint chain outside the main skeletons joint chain. This allows you to animate the foot separately from rest of the leg, while the foot as a whole can be translated via the ankle’s IKRP handle. Rather than using groups to influence the rotation of the foots joints, the reverse lock chain is parented to its respective foot joint’s IK handles, influencing their rotation.

The foot roll attribute turns out nice at the end of the reverse foot setup. There are many more steps to achieve the result though there is one linear effect to animate the foots rotation and weight placement when completed. This is easier to animate, but harder to tweak if needed. The group based control has an easier and cleaner set up, though would likely take more keys once animation began.

The reverse foot also uses a knee Pole Vector to control the position of the knee while the foot is translated and rotated in the scene. This same knee positioning can mostly be controlled by the “Twist Heel” and “Twist Toe” attributes of the group based foot control.

So both have their benefits and disadvantages. Personally I would opt for cleanliness in my scene, over the ease of a Foot Roll attribute and excess of joints. Go try them yourself! Cheers!

Local Rotation Axis

Leading up to the first exercise we should cover how to make sure our joint chains are properly oriented. Proper orientation means that the “twist” axis of a joint is the one pointing to the joints child.

Joints exist to influence the things around them via their orientation. For the purposes of rigging a character or creature joints are used in chains, where multiple joints are in a parent/child relationship making it possible to bend and twist limbs or translate an entire character.

Maya automatically consideres the X orientation of a joint as the “twist” axis for what the joint will be influencing. The Z then rotates that influenced object up or down and the Y forward or backward. This is called the XYZ orientation of the Local Rotation Axis (LRA).

X (red) points down the chain as the axis that would twist.

If Maya places a joint with the LRA incorrectly oriented the axis can be fixed by by click the “component mode” button ,

followed by the “?”

Both are located on the far right of their respective areas.

To view the LRA of a joint  navigate to Display > Transform Display > Local Rotation Axis.

Keeping everything oriented correctly will make the animation faze of the project much smoother. Deformations will also be predictable and your animators will know what to expect when you hand the scene off to them. When playing with all of these rotation axis, it is important to remember to switch back out of component mode. If you don’t, you will find yourself freaking out that things don’t select properly and all you can select on your geometry is the UVs. This is a similar frustration to storming around the house yelling about how you can’t find your wallet only to discover that it is in your hand. Just make it habit to switch out once everything is oriented properly.

You can also move single joints in your chain without effecting the parent or child by hitting the “home” key (mac) or “insert” (PC). This is the same key you hit to effect the pivot of an object in object mode.

Off to work now, more in a day or two. Go play!

Maya Overview

So, to start out it’s important to understand more or less how Maya works. Remember we are pretty much following along with The Art of Rigging Vol. 1, as my primary source of learning. So, there is a lot of supplementary information in the book! These are my general notes and thoughts to clarify and help comprehend the material covered there,  Hope it helps! Buy their book!

Maya has a node based structure that makes things work based on hierarchies and connections. If this moves then that moves, when this turns that turns, kind of thing. Maya gives it all a nice graphical interface which makes it easier for the non-programmer brain to understand.

There are two types of nodes to know. DAG and DG.

DAG (Directed Acyclic Graph) nodes exist within the hypergraph and outliner. They are node information about things like transforms to an object, its shape or constraints associated to it among others, and these must be arranged in linear parent/child hierarchies.

* The DAG is a riggers best friend. Through it you can easily drag different joint nodes to quickly alter a joint chains hierarchy.

The DG (Dependency Graph) is all the connections and nodes that are not displayed in the outliner.  Things like key frames, shaders, deformers, layer connections etc.

Via the Hypergraph in the DG you can manually effect the inupt/output of different nodes. You can RC (right click) on the right side of a node to show the output options, as well as clicking on the left side of the node to bring up the input options. Doing this pretty much means saying to Maya “make this node effect this area of this node” (output) or “make this node be effected in this area by this node” (input).

To bring up the hypergraph window navigate to Window > Hypergraph: Hierarchy (DAG) or Window > Hypergraph: Connections (DG).

You can toggle between the two windows by selecting a node and click one of these two buttons

These graphs exist as a way of controlling everything in your scene. Connections are key!

…And It Begins!

So here it is, in an attempt to learn, educate, and keep myself motivated, I will post here the journey that is learning how to rig.

As an amateur attempting to break into CGI, feature film and the world of character setup art, I will be diving headfirst into an endeavor that will ideally someday turn into a career.

So here is a little of my history:

I am a college graduate with a degree in Art and Visual Technology. My interest in digital art and animation has been with me since elementary school. The earliest memories of fascination with the art form came from full motion videos in video games like Final Fantasy VII, and Xenogears, though even earlier than that I would be plastered to the TV immersed in the world of Reboot and Bump in the Night on Saturday mornings.

My real world experience with the art form has been more recent. I have a bit over three years experience in Maya and much more than that in the “fine arts”.

My college career began with an attempt at a degree in Political Science, which may have been a better path to stay on being that I am located right outside of Washington D.C., but I soon realized that the world of politicians and lobbyists was not one that wished to pursue and develope into my own life.

Halfway through my undergrad I transferred back home to take up an art degree and finished, finally, after a total of five and a half years. That is where my problem lies. Post graduation I am still bartending, unable to translate the skills I developed in my undergrad into a life in the film, or any other media industry. So I jumped back into classes and I am about a quarter of the way through a two year certificate program in 3D Art and Animation.

This blog with follow my adventures, struggles, and growth through institution and self education in the world of 3D animation. I will mostly focus on rigging work that I get into, though as things that have alluded me in my three years of experience as a generalist come to light I will also share those with the community as well as my experiences trying to find work and anything else that seems more or less relevant. Hopefully I will develop something concise, from a student’s point of view that helps clear the fog for those struggling down similar paths of life while also making something that is fun to read.

We start with my journey into a book that is over four years old, but from what I understand is one that cannot be overlooked. The Art of Rigging – Vol. 1.

The book has now been out of print for a while and is difficult to find, though their website sells a PDF version for only $10 with all the video and data information included.

It can be found here: http://cgtoolkit.com/ along with other excellent information.

So cheers, I’ll be checking back soon!