Maya: Understanding Rigid & Soft Body Dynamics

Maya is an excellent program since it is difficult to animate natural movement, especially if many different elements are needed in the animation and for motion that is not necessarily the most important in the scene. Dynamic objects within the animation will either be soft or rigid bodies. These different bodies will interact with each other by using different fields. Constraints and springs can be used for complex motion.

Soft Bodies

These are objects that have flexible skin and can change shape if hit with a force or another object. The software creates this body by changing the shape into particles. It is the different particles that will be affected by forces and will cause the shape to change.  For each frame, the software will connect all of the dots and construct the shape.

Rigid Bodies

Rigid bodies will not be changed. There are 2 different types of rigid bodies: passive rigid bodies and active rigid bodies. Passive bodies can influence active ones, though they cannot be influenced or changed by other bodies. The active bodies can be influenced by other rigid bodies as well as interactions. Active bodies cannot be controlled by the user but passive bodies can be controlled through all of the key frames.

Fields

Adding fields so that the bodies interact is simple with Maya. Select the body and then choose the needed field within the field menu. This will create nodes, and these nodes can be changed as needed throughout the editing process.  It is possible to add many fields to an object.  One such field that is used in many animations is gravity. Some other fields include turbulence, newton, drag, air and radial.

Constraints

There are several different types of constraints, though these can only be applied to rigid bodies. A nail constraint will set a point in which the body will rotate. The length from this spot and the object is fixed. A pin constraint is used for 2 bodies. This will create a rigid rod between the 2 bodies. Think of this like creating a mobile with different objects at the base. A spring constraint will use a pivot point though the distance from the point to this object can contract and stretch. A hinge constraint uses an axis through the object. The axis is fixed and the object can rotate around the hinge.

Complex Shapes

It is possible to approximate complex shapes using simple geometry. By first creating the simple geometry and then creating a dynamic situation, it is possible to have the more complex objects inherit the dynamic interactions. This is advantageous for setting up scenes. To ensure that all fields do not change when transformed, make sure that the transformations are frozen. All of the fields and dynamic motions can be tweaked until the desired animation is achieved. Many times, adding more mass to the bodies and rotating them will create realistic motion.

Keyframe

Once all the motion has been completed, then this motion can be baked into the keyframes. This translates all the motion into the keyframes and works well instead of having to calculate motion. Once the baking has occurred, then keyframes cannot be affected by any dynamics.