The Mystery of the Immobile Bone in Reactor
It's a classic problem when working with Reactor in 3ds Max: you've created a perfect chain of bones for your braid, the constraints work wonderfully, but the main bone that should follow the head's animation decides to become a static anchor. The simulation runs, the braid moves with realistic physics, but that key bone remains immobile as if nailed to the ground.
The problem lies in how Reactor interprets animated objects within its collections. Simply adding the bone to the rigid body collection is not enough; it needs to be specifically configured to recognize and follow the existing animation.
In Reactor, an animated bone without proper configuration is like an actor who forgot his script in the middle of the performance
Essential Configuration for Animated Bones
For Reactor to recognize and use your main bone's animation, you need to modify its properties within the rigid body collection. It's not just about adding it, but explicitly telling it how it should behave.
- Select the rigid body: right-click on the bone in the rigid body collection
- Switch to animated mesh: in properties, change from rigid body to animated mesh
- Adjust animation quality: increase subframes for better tracking
- Verify keyframes: confirm that the animation exists on the timeline
Critical Properties of Animated Mesh
When you configure an object as an animated mesh in Reactor, you're essentially telling the physics engine hey, this object already has its own movement, just calculate the collisions.
The difference between a normal rigid body and an animated mesh is fundamental. The first is completely controlled by physics, the second follows its animation but physically interacts with other objects 😊
- Friction and elasticity: adjust for realistic interactions with the braid
- Collision tolerance: reduce for better detection with small bones
- Mass and density: low values for hair bones
- Initial velocity: keep at zero to follow only the animation
Step-by-Step Solution for Realistic Braids
If the problem persists, it's best to rebuild the configuration from scratch following a specific workflow. Sometimes Reactor needs things to be done in a particular order to work correctly.
Testing with a simplified scene first helps isolate the problem. A basic animated cube with a simple chain can reveal if the issue is specific to your scene or the configuration.
- Create test scene with animated cube and simple chain
- Add animated mesh before creating constraints
- Verify scene scale (common problem)
- Test with different types of constraints
After these adjustments, your bone should dance to the rhythm of the animation while the braid follows with realistic physics... although you'll probably discover that making realistic braids is more complicated than braiding them in real life 💇