FAQ
Frequently asked questions and answers.
General
Q: Is KawaiiPhysics free?
A: Yes, it's free to use under the MIT license. Commercial use is also permitted.
Q: What's the difference from PhysX?
A: KawaiiPhysics uses its own lightweight algorithm without PhysX. It's lighter than PhysX and has better compatibility with animations.
Q: Which UE versions are supported?
A: Each KawaiiPhysics version supports multiple UE versions:
| KawaiiPhysics | Supported UE Versions |
|---|---|
| v1.20.x | 5.3, 5.4, 5.5, 5.6, 5.7 |
| v1.19.x | 5.3, 5.4, 5.5, 5.6 |
| v1.18.x | 5.3, 5.4, 5.5 |
| v1.17.x | 5.3, 5.4, 5.5 |
| v1.16.x | 5.3, 5.4 |
| v1.14.x | 5.0, 5.1, 5.2 |
| v1.11.1 | 4.27 |
Setup
Q: What should I set as Root Bone?
A: Set the parent bone of the bone chain you want physics applied to. For example, if you want to animate hair, set a bone like head or spine_03 that is the parent of the hair bones.
Q: How do I apply physics to multiple parts?
A: Use separate KawaiiPhysics nodes for each part. This allows you to set different parameters for each part.
Troubleshooting
Q: Bones don't move
A: Check the following:
- Does the Root Bone have child bones?
- Is Stiffness too high? (Start around 0.05)
- Is the node connected in the Animation Blueprint?
Q: It's penetrating through the body
A: Set up collision. Add Spherical Limits or Capsule Limits and adjust them to match the body shape.
Q: Movement is too intense
A: Increase the Damping value. Around 0.1-0.3 is typical.
Q: Performance is poor
A: Consider the following:
- Reduce bone count
- Reduce collision count
- Disable based on distance (LOD)
Features
Q: I want wind to affect it
A: Enable bEnableWind and place a wind source in the world. You can adjust the influence with WindScale.
Q: Can I change parameters at runtime?
A: Yes, you can use functions from UKawaiiPhysicsLibrary or change them through Animation Blueprint variables.
Q: Can I share settings with Data Asset?
A: Yes, create a KawaiiPhysicsLimitsDataAsset and share it across multiple characters.
Other
Q: I found a bug / I have a feature request
A: Please report it on GitHub Issues or Discussions.
Q: Can I use it in commercial projects?
A: Yes, it's available for commercial use under the MIT license. Just include the license notice.
Q: Skirt is penetrating through legs
A: Use the Sync Bone feature added in v1.20.0. By reflecting leg bone movement to the skirt, you can prevent penetration without using collisions. Combining with BoneConstraint feature provides more natural movement.
Q: I want to control multiple bone chains with one node
A: Use the Additional Root Bones feature added in v1.17.0. You can set multiple root bones with the same parameters.
Q: Is it available on the Fab store?
A: Yes, it's been distributed on the Fab store since v1.19.0. Download from Fab.