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Physics

Constraint

Every object in the real world can move along 6 different axes, or 6 "degrees of freedom".

  • Translate X
  • Translate Y
  • Translate Z
  • Rotate X
  • Rotate Y
  • Rotate Z

A constraint limits one or more of these axes.

In Maya, the most typical form of constraint is locking a channel. This prevents this axis from changing.

  • A value < 0 means LOCKED, meaning it may not move along this axis
  • A value = 0 means FREE, meaning it may freely move along this axis
  • A value > 0 means LIMITED, meaning it may move within the limited range of this axis


Soft Constraints

Limits above 0 are referred to as "soft", because their amount of influence can be tuned using the Stiffness and Damping attributes. These can safely flex and can approach that of a hard constraint given enough stiffness and damping, but would struggle to reach a given target 100%.


Hard Constraints

Limits below 0, typically -1, are referred to as "hard", because their influence is infinite. These should never flex, as even the slightest amount of flex means the constraint has broken. Leaving the solver in a poor state, struggling to keep up.