Tribe17 Technical Paper

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Tribe 17 - Technical Paper: Rigging

Autodesk Maya 2010

By Leo Tsang

www.ltsang.blogspot.com

University of the Creative Arts RochesterUnit 3: Transcription

April 2011

Rigging was one of the integral tasks in this project in order for the members of Tribe 17 to move

and animate freely. With the unorthodox nature of each character being constructed from a range

of objects, each rig had to take into consideration the way in which their body parts interacted with

each other in order to make the characters movements believable.

RigWith a basic humanoid rig in mind, subtle changes had to be made in the placement of joints to

better serve each individual character model as a whole. Areas such as the hands needed an entirely

new setup due to the mechanical nature of their individual body parts. Additionally, some characters

required additional joints to accommodate their unique properties from a lantern hanging from the

inside of a chest, to an overhead cable ornament.

Left to right : Tribe Character A, B and C




Parenting Objects to Joints

With each joint in place, the respective body part objects were then parented to their corresponding

joint. This process was continued throughout the body following the hierarchy of objects.

The finger geometry is parented to l_thumb1, 2 and3, where the actual hand and wrist geometry are

parented to the Wrist_jnt. In turn, the l_thumb3 parented to the l_hand_jnt, is then parented to the

l_wrist_jnt. This allows the thumb and hand joints to operate independently while consistently

following the positing of the entire hand (Wrist_jnt).

Smooth Binding

Some body parts could not be relied upon with parenting to give correct movements; such as theneck, spine or individual limbs of certain characters. In this case, these body parts had to be skinned

with smooth binding to create the illusion of flexible movement.

Above: The neck, made from a tube, allows turning and twisting movements. Smooth binding the

weights to the respective joints allows the geometry to do so.




IK Handles

IK Handles were necessary to give stability to the legs and feet of each character. An ikRPsolver

extends from the hip to the ankle, where an ikSCsolver extends down the foot joints respectively

from the ankle.

A reverse foot joint is then constructed with each foot which, working in combination with the IK

handles, enables the foot to stay firmly on the ground without undesired movements. Foot roll and

lift controls are also created as a result of this process.

Controls

Once the character was fully rigged, Controls were then added in the form of Nurb Circles to provide

better control of the respective joints.

Each joint is point and orient constrained is their respective control. This allows the control to be

animated rather than the joint itself. Once each joint is constrained respectively, each control must

be then grouped in an ‘Offset’ group, which will allow the control to parent up the hierarchy without

giving double translations.

Above: l_ankle_jnt is Point/Orient constrained to l_foot_ctrl

l_foot_ctrl is grouped into l_foot_offset_grp

l_foot_offset_grp is parented to l_leg_ctrl




Set Driven Key

Another advantage to using controls is to be able to create Set Driven Key connections with custom

attributes. Each Foot Control is able to control the foot roll and lift with the custom attributes

Foot_Roll_FW and Foot_Roll_Side respectively. Other Set Driven Keys used include a Pump and

Eye_X custom attribute which controls the spring of the pump and Eye rotate X channel accordingly.

Above: The ‘Pump’ custom attribute of l_pump_ctrl is connected to the ‘Scale Y’ attribute of the

pump_grp, thereby creating a pumping action.

Final Adjustments

With the rig constructed complete with functioning controls, some final additions include changing

the colour of the controls for ease of use and visual reference. For example, all controls controlling

the left side of the character (including arms, hands, legs and feet) are coloured blue, where the

right side of the character is coloured green. This is done by enabling ‘Drawing Overrides’ in the

attribute editor.

Above: The r_shoulder_ctrl is coloured green by ‘Drawing Overrides’




Finally, some .mel scripts are added as shelves to select all of an individual character controls

quickly.

Example script to select all controls for character A:

select –r TribeA1:Master_Ctrl TribeA1:l_leg_ctrl TribeA1:l_knee_ctrl

TribeA1:l_foot_ctrl TribeA1:l_pump_ctrl TribeA1:r_leg_ctrl

TribeA1:r_knee_ctrl TribeA1:r_foot_ctrl TribeA1:c_waist_ctrl

TribeA1:c_spine_ctrl TribeA1:c_rib_ctrl4 TribeA1:c_rib_ctrl3

TribeA1:c_rib_ctrl2 TribeA1:c_rib_ctrl1 TribeA1:c_neck_ctrl1

TribeA1:l_shoulder_ctrl TribeA1:l_elbow_ctrl TribeA1:l_hand_ctrl

TribeA1:r_shoulder_ctrl TribeA1:r_elbow_ctrl TribeA1:r_hand_ctrl

TribeA1:c_neck_ctrl TribeA1:c_overhead4_ctrl TribeA1:c_overhead1_ctrl

TribeA1:c_overhead3_ctrl TribeA1:c_overhead2_ctrl

TribeA1:c_latern1_ctrl TribeA1:c_latern2_ctrl TribeA1:l_eye_ctrl

TribeA1:l_PV_CTRL TribeA1:r_PV_CTRL staff_ctrl;

- END -

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Tribe17 Technical Paper