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Curve Editor

Curves let you vary parameters along a bone chain, such as from the roots to the tips of hair or from the waist to the hem of a skirt.

Reading the Curve​

The X axis is the bone-length ratio from the RootBone (root 0 → tip 1), and the Y axis is a multiplier applied to the base value. The applied value at each position is base value × curve multiplier. X=1 is the endpoint of the longest path under the RootBone, including dummy bones; endpoints on shorter branches are below 1.

Curve Multiplies the Base ValueThe X axis is the bone-length ratio from the root (0) to the endpoint of the longest path (1). The Y axis is the multiplier applied to the base value.Base Value × Local MultiplierMultiplier1.00Root 0Tip 1Example: 0.5 × 0.1 = 0.05 (tip)

Enter a multiplier on the curve's Y axis, not the parameter's final value. The same rule applies to the examples below.

Examples​

These examples use a chain with an endpoint at X=1.

The shape and effect diagrams are schematic. They do not show simulation results or motion range. Purple marks the root and green marks the tip; each point corresponds to the same position on the shape and curve.

Hair: Reduce the Return Force Toward the Tip​

Stiffness controls how strongly a bone returns toward its input-pose shape relative to its parent bone. To preserve the shape near the root while reducing the return force toward the hair tip, lower the multiplier from root to tip. The RootBone itself follows the input pose.

Hair: Reduce the Return Force Toward the TipHair Stiffness multiplier is 1.0 near the root and 0.1 at the tip. The dashed line and hollow tip show the input pose; the solid line schematically shows the displaced shape. The return force toward the input-pose shape is stronger near the root and weaker toward the tip. The RootBone itself follows the input pose.Hair / StiffnessReduce the return force toward the tipNear rootMultiplier ×1.0Return force: HighTipMultiplier ×0.1Return force: LowInput poseMultiplier1.00Root 0Tip 1Schematic of shape and return force

For example, use root (0, 1.0) and tip (1, 0.1) keys. With a base value of 0.5, the calculation is 0.5 × 1.0 = 0.5 at the root key and 0.5 × 0.1 = 0.05 at the tip key. In the diagram, the dashed line and hollow hair tip show the input pose; the solid line shows the displaced hair. Actual motion also depends on damping, external forces, and other settings.

Skirt: Increase the Collision Radius Toward the Hem​

Radius is the collision radius used for each bone. If you want a wider collision range against the legs near the hem than at the waist, increase the multiplier toward the hem.

Skirt / RadiusThe Radius multiplier increases from 1.0 at the waist to 3.0 at the hem. The waist is the root and the hem is the endpoint of the longest path. Blue circles show bone collision radii; orange capsules show leg colliders. The schematic shows a wider collision range against the legs toward the hem; this setting does not expand the fabric.Skirt / RadiusWider collision range near the hemWaist / RootMultiplier ×1.0Hem / TipMultiplier ×3.0Collision radiusLeg colliderMultiplier3.001.0Waist (root) 0Hem (tip) 1Circles schematically show collision range

For example, use waist (0, 1.0) and hem (1, 3.0) keys. With a base Radius of 5 cm, the radius is 5 cm at the waist and 15 cm at the hem. The blue circles show the collision range around the bones; the orange capsules show the leg colliders. This does not expand the skirt fabric itself.

Setting Up a Curve​

  1. Select the KawaiiPhysics node in the AnimGraph.
  2. In the Details panel, expand the target curve under Physics Settings | Curves (Stiffness Rate by Bone Length Rate for the hair example or Radius Rate by Bone Length Rate for the skirt example).
  3. Add keys in the curve editor and edit their position (X) and multiplier (Y).
  4. Preview the motion, then adjust the base value and curve.

The graphs above use a straight line between the endpoint keys. Add keys or change interpolation to adjust the values between them.

tip

Start by tuning the overall motion with a fixed value. Add a curve when you need different behavior at the root and tip.

Supported Parameters​

These six parameters support curves. Their names below match the Details panel. All use the same bone-length ratio and multiplier model.

  • Damping Rate by Bone Length Rate — damping
  • Stiffness Rate by Bone Length Rate — return toward the input-pose shape
  • World Damping Location Rate by Bone Length Rate — world location damping
  • World Damping Rotation Rate by Bone Length Rate — world rotation damping
  • Radius Rate by Bone Length Rate — collision radius
  • LimitAngle Rate by Bone Length Rate — angle limit

For details on the curve properties (DampingCurveData, etc.), see Physics Parameters.