Sunday, 8 May 2011

Rigging with a Twist


• File Structure


When start a new project the file system must be sound and correct to allow for a good workflow.
This will hold true for any type of construction pipeline and naming conversion within character creation.

• CharacterNode01
• Grp_MODEL01
• Grp_globalMove01
• Grp_BONES01
• Grp_extraNodes01
• Grp_IK01
• Grp_controlObjects01
• Grp_cl_spine01

This would be my typical naming construction for my new character rig
On starting a new naming pipeline within my workflow, and helping me to get a good end result by starting with these eight files.
Character node; this file keeps the work area neat with a collapsible file system.

• GRP

All files will be stored as group nodes; for later use with skeletal structure and easy parenting of bones.
All my files will end with (01) as this lets me know it’s part of the main character project, not an asset like (armour, guns etc.) this would all end with (02).

• Bone Formation


On starting my new skeletal structure the first bones laid will be the left leg, from hip to toe, the new formation of bones will be named.

• Bn_l_hip01
• Bn_l_knee01
• Bn_l_ankle01
• Bn_l_ball01
• Be_l_toe01

All (bn) is for bones, named like this for the sole purpose of binding to the skin at the end of rigging.
This go’s for (be) that stands for bone end, named like this so it will not be bound to the skin also at the end of the rigging.
On setting my bones for left leg I will now check the orientation point of my joints to make sure (Y) is all in the same direction.
When the right leg is mirrored from the left leg, the (Y) will look the wrong way round but this is normal the bone chain.
At this point I will now set my (IK) handles from hip two ankles, on both legs. [1]






 • IK Handles


There are three types of (IK) handles; they each have a role to play in a character rig.

• IKRPSolver
• IKSCSolver
• IK Spline Handel

How they are defined; ikRPSolver (Rotate Plane), ikSCSolver (Single Chain) and also the IK Spline Handle.
The Rotate Plane IK Solver is the default IK Solver and is probably used the most when setting up characters; it is most useful when used in conjunction with chains in joints such as an arm (where the elbow will need to be rotated into place) or a leg (where the knee will need to be rotated into place). It essentially has the ability to control the twisting direction of the chain that it is controlling.
Also if you are adding a (Pole Vector) with a control object to your characters knees, or elbows, this will not work with an ikSCSolver (Single Chain).
As a single chain an (ikSCSolver) is best used in bones that have no need for an outside controlling influence. [1] In this case, it best served me in a reverse foot lock on my leg rig.

• IK Spline Handle


The IK Spline Handle is actually quite a powerful handle, it is best used when you would have a complex series of joints, for example a characters spine; or a character who has a tail, in both cases you would require a solver that would simplify the process of animating a lot of joints together in the same area at the same time.
When a Spline Handle is used [1] between a chain of joints, a Spline is created along the chain, and in turn the CV's (Control Vertices) are what would be selected and manipulated for animating with, generally the CV's would in turn be constrained to Cluster Deformers for ease of use when manipulating for animation.
[1]


• Point Constraints

• Aim Constraints
• Orient Constraints
• Aim Constraints
• Scale Constraints
• Geometry Constraints
• Normal Constraints
• Tangent Constraints
• Pole Vector Constraints



As the Maya Online Help states 'Constraints enable you to constrain the position, orientation, or scale of an object to other objects. Further, with constraints you can impose specific limits on objects and automate animation processes.' Constraints are used quite a lot in animation and character setup, and its worthwhile getting to know how they all work, so you can best utilise them within your scenes. Maya offers a number of different types of constraints, these are;


• Point constraints

Point constraints constrain an object's position to the position of one or more objects. For example, constraining a button to a characters shirt.

• Aim constraints

Aim constraints constrain an object's orientation so that it always aims at other objects. For example, constraining eyes on a character so that they always look in a particular direction.

• Orient constraints

An orient constraint causes an object to follow the orientation of one or more objects. For example, a crowd scene may require all characters to look in a particular direction at the same time, you can orient constrain all the heads to one main character.

• Scale constraints

A scale constraint causes an object to follow the scaling of one or more objects. For example, constraining two characters together so that when grows (scale Y), the other grows too.

• Geometry constraints

A geometry constraint restricts an object to a NURBS surface, NURBS curve, or polygonal surface (mesh). For example, constraining a drinks can to a characters hand.

• Normal constraints

Normal constraints constrain an object's orientation so that it aligns with the normal vectors of a NURBS or polygonal surface (mesh). For example, constraining a spider to a character to get it to walk over the surface correctly.


• Tangent constraints

Tangent constraints constrain an object's orientation so that the object always points in the direction a curve. For example constraining a fly character to a curve so that it animates along the curve and keeps the direction that the curves holds, i.e. if it goes up, the fly character would be facing up.

• Pole vector constraints

A pole vector constraint constrains an IK rotate plane handle's pole vector. For example, controlling the position of a Characters knee or elbow when animating

• Control Objects

When using control objects, this can be a number of different setups.
It can be all the moving parts outside a characters body, down to something as small as lips, or fingers.
Many different shapes can be used, or objects of your chose, it is limitless
However it is also helpful to colour your bones as well as the control objects, this helps the animator define (right & left) in the animation sequence. [2]-[1]

• Advanced Body Rotations

• Advanced Forearm Twist

These are setup in character expression that deals with parts of the body in the script editor.
In advanced body rotation [1] it will be from the neck down to the waist of your character rig using normal polygon primitives, such as a cube.
I used four cubes on my rig to give me 0.06 degrees twist from the neck down to 0.01 degrees twist at the waist, so the spine will rotate nicely when turning the chest or head using the control object.
As for the forearm twist [1] it was a bit simpler, only 0.03 degrees twist when the hand is rotated, this gives it a more natural look to the movement.
There are many more things I can go into that deal with rigging but I will save it for the next time.



• N.G.C.R Rigging Layout

• Bone Hierarchy


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