Mode - Chain

The Chain mode utilizes a custom physics engine to provide natural and artistically-controllable FK chain simulations. It allows for detailed control over various aspects of the chain's dynamic behavior, enabling the creation of realistic secondary motion with detailed artistic control.

It's best suited for simulating tails, antennas, tentacles, chains, ropes, hair and similar, however it can also be used on spines, heads, arms, legs to give some physics and life to various kinds of objects that are connected to each other.

It simulates and FK chain, however your selected objects don't even have to be an actuall FK chain, it will work with any rig, even if your selection has no hierarchy, uses IK or anything like that. BroDynamics will internally handle that, and output required positions and rotations for your selected transforms.

Technically, this mode simulates the chain as a series of interconnected physics bodies, each reacting to forces and constraints defined by the attributes below.

Selection order is important!

You need to select objects in the correct order, starting from the root of your chain and progressing to the tip. "Select Hierarchy" may not work reliably with complex rigs.

Preroll is recommended

Adding a short preroll (1-3 seconds) before your main animation can help the simulation settle and prevent initial jarring movements or artifacts.

Simulating several chains at once

Chain mode can simulate many chains together in one shared world, with collisions between them. Mark your chains once with the Chains menu, then select them and click Simulate. See Multi-Chain Simulation.

Quick start: the controls that matter¶

Most chains can be tuned with just the controls at the top of the properties panel. Everything else lives in collapsed groups below them and can usually stay at its defaults.

Spring Stiffness and Motor Stiffness decide how tightly the chain follows your animation. Lower = looser, more lag; higher = tighter.
Follow Damping Ratio decides how bouncy that follow is. Lower = more overshoot and follow-through; 1.0 = no overshoot.
Curves (in the Curves group) shape all of the above from root to tip. The defaults already give a firm base and a loose tip.
Radius only matters if you use colliders. Turn on Show collider radius (in Tools → Objects) to see it in the viewport.
Use the Preview button to tune these live while Maya plays, then click Simulate to bake.

What changed in damping (if you used older versions)

Damping used to be set by hand with Spring Damping and Motor Damping. That made it easy to end up with an under-damped chain that lags behind fast motion and then snaps to catch up, which looked like jitter.

Damping is now automatic. With Auto Follow Damping on (the default), the spring and motor damping are calculated from their stiffness and the single Follow Damping Ratio control. Together with Interpolate Guides and the new default of 4 Substeps, this removes the lag-then-snap jitter.

Spring Damping and Motor Damping have moved to the Fine Tuning group and are greyed out while Auto Follow Damping is on.
Linear Damping and Rotation Damping have also moved to Fine Tuning. They still apply on top of Follow Damping, as extra drag.
To get the old manual behavior back, turn off Auto Follow Damping in the Solver group. Presets saved with older versions still load, but their Spring and Motor Damping values are ignored until you do this.

Simulation Properties¶

Properties are listed in the order they appear in the UI. The main controls come first, followed by collapsible groups.

Main controls¶

Spring Stiffness¶

How strongly the chain follows the desired shape.

Higher values pull links harder back to the guide path, making the motion tighter and less floppy. This is the stiffness of the positional spring that pulls each link back toward its animated position. Shaped root-to-tip by the Spring Stiffness Curve.

Use lower stiffness for loose tails and hair, higher stiffness for tails or antennae that should closely match the guide.

Follow Damping Ratio¶

The main damping control: how quickly the chain settles as it follows the guide.

With Auto Follow Damping on (the default), this one value sets both the spring and the motor damping as a fraction of critical damping. You usually don't need to touch any other damping control.

1.0: critically damped. No overshoot, fastest clean catch-up.
Below 1.0: some springy overshoot and follow-through. Lower means bouncier.
Above 1.0: over-damped and sluggish.

Default is 0.8. It is multiplied per link by the Follow Damping Ratio Curve, which by default drops toward the tip, so the tip is livelier than the base.

Radius¶

Collision radius of each link.

Controls how thick the chain is for collisions, without changing the visible mesh. Shaped root-to-tip by the Radius Curve.

Radius only affects collisions. If collisions are disabled or nothing is touched, changing Radius does not change the motion.

Use Show collider radius (see Tools) to see the actual collision capsules in the viewport while you adjust it.

Mass¶

How heavy each link is.

Heavier links resist changes in motion and keep more momentum. Increase for thick tails, heavy cables or armor pieces. Decrease for light hair strands or ribbons that should react quickly. Shaped root-to-tip by the Mass Curve.

Motor Stiffness (kp)¶

How strongly each link is rotated toward the guide orientation.

The orientation motor works like a powered hinge that turns each link toward its animated rotation, while still allowing overlap and lag. Higher values track the guide rotation more tightly. Lower values let soft, floppy tails drift behind. Shaped root-to-tip by the Motor Stiffness Curve.

Cycle Iterations¶

Helps to seamlessly cycle your simulation.

0 means no cycling. At 1 or more, the simulation runs several times, smoothing out the transition between the first and last frame so the result loops. More iterations take longer and give a smoother loop. Usually you won't need more than 2 to 5.

During Realtime Preview, any value of 1 or more also makes the preview flow across the loop instead of resetting at the start of the timeline.

Solver¶

These properties affect stability, accuracy and performance of the internal solver.

Max Angular Speed (rad/s)¶

Safety limit for how fast links can spin.

Clamps rotational speed to prevent extreme spinning, or to limit how fast the chain can bend. The default is extremely high, which effectively disables it.

World Compliance¶

Global softness added to all constraints.

0 is fully rigid. Very small positive values allow a tiny amount of stretch, which can help remove jitter and numerical explosions. Keep this extremely low.

Substeps¶

How many physics steps are used per frame.

More substeps improve collision detection and make constraints and angle limits more accurate, at the cost of speed. The default is 4. Below 4, simulation is faster but collisions may be missed. If colliders are in the list and Substeps is below 4, the Substeps field is outlined in red and its tooltip explains why.

True Substeps¶

Moves the Maya timeline in substep increments while baking.

Normally every substep is simulated with the guide and colliders at the current frame's pose. With True Substeps on, Maya's current time moves by 1/substeps for each physics step, so animated guides and deformable (skinned) colliders are evaluated at their real in-between poses.

Use it when a very fast guide or a skinned collider needs accurate mid-frame motion. It is slower: deformable colliders are rebuilt every substep, and keys are written at every substep time (the curves get N times more keys, which the Simplify Curve Filter then cleans up). Preview and static colliders are not affected.

Interpolate Guides¶

Moves the guide smoothly between frames during substeps.

When on (the default), each substep moves the guide part of the way from the previous frame's pose to the current one, so the chain tracks fast motion continuously instead of lagging behind and snapping to catch up.

Unlike True Substeps, this needs no extra evaluation in Maya and also works in preview. It does not resample skinned colliders mid-frame. Requires Substeps greater than 1.

Auto Follow Damping¶

Critically damps the guide-follow automatically.

When on (the default), the position-spring and orientation-motor damping are calculated from their stiffness and the Follow Damping Ratio, so the follow can't be accidentally under-damped. This overrides the manual Spring Damping and Motor Damping values, which are greyed out while it's on.

At low substep counts the calculated damping is capped for stability. If you run very stiff motors, raise Substeps or keep Interpolate Guides on to reach full damping.

Solver Iterations¶

How many times constraints are solved per substep.

Higher values make joints and contacts stiffer and cleaner, but cost more time. Increase if joints feel rubbery or penetrations are not resolving. Lower it for faster previews.

Collision Pre-Iterations¶

Extra collision-only passes before the main solve.

Helps chains rest cleanly on colliders. Increase if tails jitter or sink when resting on the ground. Set to 0 if you need maximum speed and contacts are simple.

Implicit Gyroscopic¶

More accurate integration of spinning links.

When on (the default), rotational energy is preserved accurately, which keeps fast-spinning links (especially tips) stable.

When off, links lose rotational momentum faster and the chain may feel more settled. If a chain feels too lively or elastic, try turning it off. Very fast spinners can become unstable with it off.

Contact Warm Start¶

Reuses collision impulses between substeps.

On by default. It improves resting contacts and reduces jitter at no extra cost. Turn it off if a chain sliding or rolling along a collider looks grabby or jittery.

Exact Inertia¶

How rotational inertia is computed for polygon (Trimesh or Convex Hull) bodies.

On by default, using the exact solid inertia, which is accurate for closed, consistently-wound meshes. Turn it off if a mesh-based body loses its spin or rotates strangely; a broken mesh can make the exact inertia wrong.

Fine Tuning¶

Secondary damping controls. With Auto Follow Damping on, you usually don't need any of these.

Spring Damping¶

Manual damping of the position spring.

Ignored (greyed out) while Auto Follow Damping is on. Only use it if you turn Auto Follow Damping off and want to tune spring damping by hand. Shaped root-to-tip by the Spring Damping Curve.

Linear Damping¶

Extra drag on linear motion.

Applies on top of Follow Damping as a separate drag on movement. Increase to make tails heavier and slower to settle. Reduce toward 0 for the liveliest motion. Shaped root-to-tip by the Linear Damping Curve.

Rotation Damping¶

Extra drag on rotations.

Applies on top of Follow Damping as a separate drag on spinning. Higher values make motion settle faster; lower values keep it lively and loose. Shaped root-to-tip by the Rotation Damping Curve.

Motor Damping (kd)¶

Manual damping of the orientation motor.

Ignored (greyed out) while Auto Follow Damping is on. Only use it if you turn Auto Follow Damping off. Increase to remove ringing; decrease for more springiness. Shaped root-to-tip by the Motor Damping Curve.

Environment¶

Air Density¶

Strength of drag from the surrounding medium.

0 disables drag. Higher values simulate moving through air or water, delaying and slowing down motion. Typical air is around 1.2. Use higher values for underwater or very heavy motion.

Gravity (cm/s²)¶

Downward gravity strength.

Applies gravity along negative Y. 0 (the default) means no gravity, so the chain is driven only by the character. Use values around 9.8 for Earth-like gravity, or lower for stylized, low-gravity motion.

Collisions & Contact¶

These properties control how the chain interacts with colliders and with itself.

Friction¶

How sticky contacts are when the chain touches colliders.

Controls both how hard it is to start sliding and how quickly sliding slows down. Increase to make tails grip the ground or props; decrease for icy, slippery surfaces.

Capsule Gap (%)¶

Gap between neighboring link capsules.

Trims part of each capsule along the chain so adjacent links don't constantly collide with each other. The total gap between two capsules equals this percentage of the segment length. Higher values reduce self-contact noise, but too high can leave visible gaps if you rely on self-collision. The capsules drawn by Show collider radius include this gap.

Restitution (Bounciness)¶

How much the chain bounces on impact.

0 means no bounce, 1 is perfectly elastic. Keep near 0 for tails and hair; increase slightly for playful, cartoony bouncing.

Enable Self-Collision¶

Allow the chain to collide with itself.

Links push against each other instead of passing through. Useful for braids, cords and dense bundles, but slightly more expensive. Leave off for simple tails or antennae.

Note

In multi-chain simulation, self-collision is set per chain on its marker, and this checkbox is not used.

Contact Damping (Linear / Angular)¶

Extra damping applied only on substeps where a contact happens.

0 does nothing, 1 stops motion on impact. Helps remove pops, fast sliding and sudden spins when the chain hits geometry, without over-damping the whole motion.

Contact Damping Velocity Thresholds (Linear / Angular)¶

Minimum speed before contact damping is applied.

Keeps slow resting contacts smooth while still damping big, fast hits.

Limits¶

These settings control how far links can bend and twist relative to each other, and how soft those limits are.

Enable Swing Limits / Swing Limit (deg)¶

Limit how far links can bend away from the chain direction.

When enabled (the default, at 25°), bending between links is clamped so the chain can't fold back on itself. 180 effectively disables the limit. Use smaller angles for stiff mechanical chains and larger ones for flexible tails or whips. Shaped root-to-tip by the Swing Limit Curve.

Enable Twist Limits / Twist Limit (deg)¶

Limit how much links can twist around their own axis.

Off by default. Enable for cables or spines that shouldn't endlessly twist; keep disabled for ropes or tentacles where spin is part of the look. Shaped root-to-tip by the Twist Limit Curve.

Anchor Position Compliance¶

Softness of the joint connection between links.

Very small values keep the chain length visually rigid. Slightly higher values allow tiny stretching, which can look better in motion.

Swing Compliance (Softness) / Twist Compliance (Softness)¶

Softness of the swing and twist limits.

Lower values hold the limit tightly; higher values let the chain push past it a little, which helps if hard limits cause popping or snapping. Shaped root-to-tip by their curves.

Curves¶

Every curve multiplies its matching property per link. The horizontal axis is the position along the chain (0 = root, 1 = tip) and the vertical value is the multiplier.

Curve	Multiplies	Default (root → tip)
Spring Stiffness Curve	Spring Stiffness	1.0 → 0.1
Follow Damping Ratio Curve	Follow Damping Ratio	1.0 → 0.1
Spring Damping Curve	Spring Damping	1.0 → 0.5
Linear Damping Curve	Linear Damping	1.0 → 0.5
Rotation Damping Curve	Rotation Damping	1.0 → 1.0
Mass Curve	Mass	0.5 → 1.0
Radius Curve	Radius	1.0 → 1.0
Swing Limit Curve	Swing Limit (deg)	1.0 → 1.0
Twist Limit Curve	Twist Limit (deg)	1.0 → 1.0
Swing Compliance Curve	Swing Compliance	1.0 → 1.0
Twist Compliance Curve	Twist Compliance	1.0 → 1.0
Motor Stiffness Curve	Motor Stiffness	1.0 → 0.5
Motor Damping Curve	Motor Damping	1.0 → 0.5

A common pattern is stiffer and more damped at the base, softer and livelier at the tip, which is what the defaults do. Inverting the Motor Stiffness Curve (weak base, strong tip) gives expressive, tentacle-style motion.

Advanced¶

Use Position Spring¶

Follow the guide with a positional spring.

Leave on for most setups. Turn off for orientation-only following, where the chain should match the guide's rotation but isn't forced to sit exactly on the guide path.

Use Orientation Motor¶

Follow the guide orientation with a rotational motor.

Gives natural motion as the chain relaxes toward the target shape.

Motor Affects Parent¶

Push back on the guide when the motor acts.

Applies equal and opposite torque to the guide. Keep off for guides driven by animation, which is nearly always the case.

Motor Max Angular Acc (rad/s²)¶

Safety clamp on how violently the motor can spin a link.

Lower it if you see sudden flips or harsh snaps when the guide moves quickly.

Fixed Base¶

Keep the first link locked to the animation.

The base follows the animation exactly while the rest of the chain simulates from it. Leave on for tails, antennae and straps attached to a character; turn off only when the whole chain should be free.

Shape Smooth Strength / Shape Smooth Iterations¶

Per-frame smoothing of the chain's shape.

Evens out kinks between neighboring links during the simulation, separately from the curve filters applied after baking. 0 disables it; the default is 0.3 with 2 iterations. More iterations give smoother shapes at a small cost in speed.

Baking¶

These properties affect how results are written back to your original objects.

Smoothing (Filter)¶

Butterworth filter strength for baked animation curves.

Higher values smooth more, removing noise but also small details. Set to 0 to disable the filter.

Euler Filter¶

Runs Maya's Euler Filter on baked rotation curves.

Removes 360-degree flips and keeps rotations continuous. Recommended on for most rigs.

Simplify Curve Filter¶

Runs Maya's Simplify Curve Filter on all baked curves.

Reduces keyframe density and small jitter, giving animation that's easier to tweak. Especially useful with True Substeps, which writes extra keys.

Match Positions¶

Writes simulated positions back to the original objects (TX/TY/TZ).

Enable when you want both position and rotation driven by the chain.

Match Rotations¶

Writes simulated rotations back to the original objects (RX/RY/RZ).

Usually enabled, since orientation drives most of the visible motion.

Realtime Preview¶

Chain mode can run the simulation live in the viewport, driven by Maya's own playback, so you can tune properties without baking.

Select your chain controls (root to tip), the same way you would to simulate.
Click the Preview button next to Simulate.
Press Play in Maya. The chain is simulated as the timeline plays.
Adjust properties while it plays. Most changes apply immediately.
When you're happy, click Simulate to bake keys. Starting a bake automatically stops the preview.

How the preview behaves:

Nothing is keyed. The preview temporarily disconnects the animation from the channels it drives, and reconnects it when the preview stops.
Scrubbing or jumping back in time resets the chain to its animated pose at that frame.
Looping: with Cycle Iterations set to 1 or more, the preview keeps flowing when playback wraps around, so you can watch a cycled animation loop seamlessly.
Live vs rebuild: most properties update instantly. Changing Radius, Radius Curve, Capsule Gap, Fixed Base, Self-Collision, Use Position Spring, Use Orientation Motor, Motor Affects Parent, Match Positions, Match Rotations or the collider list triggers a short rebuild.
Colliders are treated as static during preview, even if Deformable is enabled. Deformation is used when baking.
The preview simulates one chain at a time. Multi-chain simulation is available when baking.
The preview stops when you click the button again, switch modes, click Simulate, or open a new scene.

Tools¶

The Tools section provides extra tools for working with this simulation mode.

Static Colliders¶

Use the Colliders object list to add static meshes to the environment.

These meshes are converted to static rigid bodies and used as obstacles for dynamic objects. They share friction and restitution values with dynamic bodies for consistent behavior.

To speed things up you can create low poly meshes to use as colliders. These can be skinned, deformed or shrinkWrapped to the original mesh if needed.

You can use 3 types of static colliders:

Trimesh - this mode is the default, and uses all triangles from the provided mesh for collision detection, with full support of concave shapes and even holes. However it's more expensive than Convex Hull to calculate, and its performance depends heavily on how many triangles are in the mesh. Use it with meshes with concavities (like stairs) or holes (like a donut shape). It is recommended to use lower poly versions of existing meshes as colliders if you need to speed up the simulation.
Voxbox - this mode creates a grid of box colliders, like voxelizing the mesh (like a Minecraft world). It's slower than Trimesh or Convex Hull for low and mid poly objects, but its performance scales better with mesh density. Use this mode when you need to simulate collisions with high detail meshes. It supports concave meshes just like Trimesh. On lower quality settings it can produce jagged collision surfaces.
Convex Hull - this mode uses only convex shapes for collision detection. This means that it can't handle concavities or holes, but it's much faster than Trimesh. Use this mode with simple convex objects.

Voxbox is the only mode that has extra settings:

Grid - voxel resolution, i.e. how many cells the mesh's bounding box is divided into per axis. Higher values = finer detail.
Multi-axis - voxelizes the mesh along all three axes and combines the results, which fills thin or open meshes more reliably.
Merge - merges neighboring voxels into larger boxes, so fewer boxes are needed.
Max boxes - maximum number of boxes to use in the collider.

Each collider type has a Deformable checkbox (on by default for Trimesh, off for Voxbox and Convex Hull). When enabled, the shape of the object is read from Maya every frame and the collider is updated. Disable it if your colliders are not moving or deforming, to speed up the simulation.

The Open Collider Generator button opens a small tool that builds simplified convex collider meshes from a mesh or vertex selection, which you can then add to the Colliders list.

Show collider radius¶

Turn on Show collider radius (below the collider settings) to draw the chain's collision capsules in the viewport, so you can see how thick the chain really is for collisions.

It follows your current selection: select the chain controls to see their capsules.
It updates live as you change Radius, Radius Curve or Capsule Gap, and as you move or scrub the controls.
It's only a viewport helper. Nothing is saved into the scene, and it doesn't affect the simulation.
It is hidden while Realtime Preview runs and comes back when the preview stops.

Chains marked with the Chains menu always show their own colored capsules, independent of this checkbox. See Multi-Chain Simulation.