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Overview

Step Modifier creates procedural steps to avoid feet sliding when changing animation states (e.g., standing to crouching).

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Bone References

Here you will find bone references to assign.
  • Pelvis — pelvis or hip bone.
  • Right and Left Foot IK Target — IK bone for the right or left foot. It’s usually set to IK foot_r or IK foot_l.

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Ground Alignment

Here you will find settings for snapping feet to the ground.
  • Right Foot — right foot bone (not an IK).
  • Left Foot — left foot bone (not an IK).
  • Leg Stretch Factor — fine-tunes how aggressively the system detects and corrects leg stretching. Higher values increase the likelihood that a leg will be classified as “stretched” and have its length adjusted accordingly.

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Step Motion

Here you will find animation curves for feet and pelvis.
  • Lead Foot Motion — position animation for the leading foot (the one making a step first).
  • Follow Foot Motion — position animation for the following foot (the one making a step after the leading one).
  • Pelvis Motion — position animation for pelvis.
Note: The Animation Curve values must at end zero for all motions.
  • Lead, Follow Foot and Pelvis Scale — values that will scale each motion per-axis. For example, the X component will scale the X axis.
  • Play Rate — speed multiplier for this step motion.

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Stride Settings

Here you will properties that define the procedural step.
  • Animated Lead Foot — defines the leading foot for this step. A leading foot is the one making a step first.
  • Force Lead Foot — controls if the step must always start with a leading foot. If disabled, the leading foot will be determined based on the velocity vector.
  • Max Allowed Strength — defines the max allowed step length. If exceeded, feet will be moved in the movement direction to avoid stretching.
  • Max Allowed Offset Angle — defines the max allowed character rotation to avoid leg twisting. If exceeded, feet will be rotated around pelvis to compensate the rotation.
  • Step Cooldown Rate — time in seconds needed to pass before making the next step.

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Use-cases

Step Modifier can be used for any situation to replace feet sliding with a nice procedural step. Here are most popular applications:
  1. Movement stop or start transitions.
  2. New stance transition (e.g., going from rifle to sword, or from standing to crouching).
  3. Turning in place.
Tip: CAS comes with example Step presets, these can be found in KINEMATION/CharacterAnimationSystem/Examples/Steps/.
To get best results, make sure that:
  1. MaxAllowedStride is set to ~0.3-0.4 to avoid character legs being strecthed. Setting this to a too small number will result in abrupt, unnatural steps.
  2. MaxAllowedOffsetAngle is set to ~45 degrees to avoid legs being twisted.
  3. StepCooldownRate is set to ~0.3-0.4s to handle player input-spamming situations.
  4. Force Lead Foot can be used for specific cases, like turning in place — we only want to turn right with the right foot, and vice versa.
  5. All animation curves start at zero for a seamless transition.
These settings might differ from one character model to another, so it’s fine to experiment and find what works best for your character.

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How to play steps

Steps can be played at runtime using by updating the animation modifier: It’s possible to play steps when a transition is entering or exiting a state in the Animator: This feature is used in the CAS Demo to play steps when turning in place or finishing climbing.