Controls global substeps at the simulation level, as opposed to the Bullet-specific substeps. Global Substeps are best used when you need to export the substepped geometry. They will use more memory per frame, however, all the substeps will be kept rather than just the final values each frame.

• Increasing the number of Global Substeps can be useful if you want custom solvers (i.e. in the dive target) to be substepped.

• The Bullet Substeps are performed for each global substep, so you may want to decrease the number of Bullet Substeps accordingly when increasing the number of Global Substeps to avoid increasing the total number of Bullet Substeps.

• If you only want to perform more Bullet Substeps, it’s more efficient to use one global substep and increase the number of Bullet Substeps.

The number of substeps for each simulation step, used by Bullet internally. Increasing this number will increase the resolution of the simulation.

Increasing the number of substeps is one way to help fix problems of collisions not being detected for quickly moving objects.

The more iterations you use, the more accurate the constraint and collision handling will be.

Solve on simulation start frame.

When this checkbox is turned on, input simulation geometry and constraint geometry available at the current frame will be added to the simulation. A suffix "_" + int(frame * 100) will be appended to their names. For example, piece0-1 at frame 1 will be renamed piece0-1_100, while piece0-1 at frame 2.5 will be renamed piece0-1_250.

When this checkbox is turned on, RBD pieces that are duplicated (or re-emitted) during the course of the simulation will be output correctly. Replicated RBDs with a non-unique name attribute will have a "_r" + replica number suffix appended to their name. For example, if the RBD with a piece0 name is replicated 3 times, the 3 new RBD pieces will be named piece0_r1, piece0_r2 and piece0_r3.

Specifies how much memory in megabytes can be consumed by the cache for this simulation. Once this limit is exceeded, old cache entries are deleted.

A padding distance between shapes, which is used by the Bullet engine to improve the reliability and performance of the collision detection. You may need to scale this value depending on the scale of your scene. This padding increases the size of the collision shape, so it is recommended to enable Shrink Collision Geometry to prevent the collision shape from growing.

This option is not available for Plane geometry representations.

The mass of an object is its volume times its density.

An object will often acquire a spin when it receives a glancing blow. The amount of spin acquired depends on the shape and mass distribution of the object, known as the inertial tensor.

The Rotational Stiffness is a scale factor applied to this. A higher stiffness will make the object less liable to spinning, a lower value will make it more ready to spin.

The elasticity of the object. If two objects of bounce 1.0 collide, they will rebound without losing energy. If two objects of bounce 0.0 collide, they will come to a standstill.

The coefficient of friction of the object. A value of 0 means the object is frictionless. This governs how much the tangential velocity is affected by collisions and resting contacts.

The specified point attributes are copied from the input geometry to the simulation geometry at each frame. This can be useful to animate attributes such as active at the SOP level to activate pieces at a particular frame.

The sleeping threshold for the object’s linear velocity. If the object’s linear speed is below this threshold for a period of time, the object may be treated as non-moving.

The sleeping threshold for the object’s angular velocity. If the object’s angular speed is below this threshold for a period of time, the object may be treated as non-moving.

Enables the collision object.

Specify, if the collision object is animated, deforming or static.

The shape used by the Bullet engine to represent the object.

The elasticity of the object. If two objects of bounce 1.0 collide, they will rebound without losing energy. If two objects of bounce 0.0 collide, they will come to a standstill.

The coefficient of friction of the object. A value of 0 means the object is frictionless.

This governs how much the tangential velocity is affected by collisions and resting contacts.

The specified point attributes correspond to the solver node’s fourth input. The attributes are copied from the input geometry to the simulation geometry at each frame. This can be useful to animate attributes such as active at the SOP level to activate pieces at a particular frame.

Choose, which type of ground collision you want to use.

SOP path to the height field geometry.

Enable deforming heightfield geometry.

The location of the center of the ground plane.

The rotation of the ground plane.

The elasticity of the object. If two objects of bounce 1.0 collide, they will rebound without losing energy. If two objects of bounce 0.0 collide, they will come to a standstill.

The coefficient of friction of the object. A value of 0 means the object is frictionless.

This governs how much the tangential velocity is affected by collisions and resting contacts.

An object sliding may have a lower friction coefficient than an object at rest. This is the scale factor that relates the two. It is not a friction coefficient, but a scale between zero and one.

A value of one means that dynamic friction is equal to static friction. A scale of zero means that as soon as static friction is overcome the object acts without friction.

Turn on this checkbox to use gravity for your simulation.

The amount of force to apply to a unit-massed object. Because the force is scaled by the mass, objects will undergo this acceleration.

If your units are meters, seconds, and kilograms, -9.81 is a good value for Earth’s gravity. If your units are feet, seconds, and pounds, -32 is a good value for Earth’s gravity.

Turn on this checkbox to use drag for your simulation. Drag works similar to air friction and can decelerate moving objects.

Enable the POP Drag DOP.

The speed which the particles will be dragged to. If it is zero, they are dragged to a stop. Otherwise, it defines a wind speed which the particles will accelerate to.

Ignores any mass on the RBD pieces.

Since forces are stored as force rather than accel (acceleration), this is done by multiplying the force by the mass attribute. This will then be canceled out by the solver.

airresist will also be similarly multiplied.

Ignoring mass ensures that small pieces of an RBD object move at the same speed as big pieces. This makes for a more controllable simulation.

Use VEX expressions to modify the drag parameters.

Turn on this checkbox to use drag spin for your simulation. Drag spin works similar to air friction and can decelerate spinning and rotating objects.

How quickly the particle should match the goal spin speed.

The desired axis for the particle to spin around in its rest state.

How fast (degrees per second) the particle should spin around the given axis when it has reached its rest state. If this is zero, it will drag the spin to a stop. If it is positive, it will spin-up or down until it matches this.

The provided goal axis will be rotated into the particle’s own reference frame. Thus a value of (0, 1, 0) will be up in the space of the particle rather than in world space.

Use VEX expressions to modify the drag spin parameters.

Turn on this option to enable break thresholds on solver level.

This controls the number of breaking conditions which can be run on various constraint groups. Click the + and - buttons to add and remove breaks. Press Clear to remove all breaks at once.

Constraint names for which constraint breaking will be computed.

Constraint primitives to be evaluated for breaking.

Break constraints at the specified frame.

Breaking will only be evaluated from the specified frame onward.

The angle (in radians) beyond which a constraint will break.

The name of the attribute used to multiply the angle threshold with.

The distance between anchor points beyond which a constraint will break.

The force beyond which a constraint will break.

The impact beyond which a constraint will break.

The torque beyond which a constraint will break.

The linear plastic flow beyond which a constraint will break.

The angular plastic flow beyond which a constraint will break.

When turned on, you can manipulate the constraint geometry primitives with a VEX snippet. This is similar to adding a Geometry Wrangle DOP in the dive target.

The SOP path to the VEX snippet you want to use for manipulating constraint geometry primitives.

The specified point attributes are copied from the input geometry (solver’s second input) to animated constraints geometry at each frame. This can be useful to animate attributes such as active at the SOP level to activate pieces at a particular frame.

Constraints that are broken by the solver are deleted from the constraint geometry by default. This option keeps those constraints in the geometry, in a primitive group named broken. This can be useful for driving secondary effects based on which constraints have broken.

When the distance between the computed guided position and the resulting post-solve position is greater than the linear threshold multiplied by guide strength, the piece will become unguided.

When the angle (in degrees) between the computed guided orientation and the resulting post-solve orientation is greater than the angular threshold multiplied by guide strength, the piece will become unguided.

When the difference between the distance of the guide piece to the bullet primitive and their distance at rest increases beyond the distance threshold multiplied by guide strength, the piece will become unguided.

When the accumulated distance between the computed guide position and the resulting post-solve position is greater than the distance threshold multiplied by guide strength, the piece will become unguided.

When the accumulated angle (in degrees) between the computed guide orientation and the resulting post-solve orientation is greater than the angular threshold multiplied by guide strength, the piece will become unguided.

When the accumulated difference between the distance of the guide piece to the bullet primitive and their distance at rest increases beyond the distance threshold multiplied by guide strength, the piece will become unguided.

Deletes constraints between pieces belonging to different guide clusters.

Constraint geometry primitives to consider when removing intra-guide constraints.

Turn this option on to display the collision geometry.

Runs a VEX snippet after the guiding computation has occurred. This enables you to modify the computed velocity or target velocity for better control over the resulting guided behavior.

Only affect a group of bullet packed primitives. By default, the guided group is selected to only affect primitives currently being guided.

Displays the bullet geometry representation used by the solver.

Displays active pieces as a green wireframe overlay.

Displays sleeping pieces as a red wireframe overlay.

Turn on this option to create an infinite ground plane for collision.

The ground plane’s visualization can be Wireframe or Shaded.

When turned on you will see the geometry of the objects, wired to the solver’s fourth input. You can change the display color under Color.

Turn on the checkbox for a flat shaded representation of the objects, wired to the solver’s fourth input.

Choose a color from the picker or define a RGB value to dye the collision geometry.

Turn on the display of the constraint geometry.

Displays the guide geometry to represent the constraints (e.g. the same as what you would see from the Constraint Network DOP). This displays different geometry depending on the constraint type - for example, soft constraints display geometry to indicate the position and orientation of each anchor.

Displays guide geometry, connecting each constraint anchor to the object it is attached to.

Scales the size of the guide geometry.

Displays guided pieces as a blue wireframe overlay.

Displays the guided geometry transformed by the guide (no simulation). The hue represents the guide clusters, the value represents the strength attribute value. In this mode, the viewport inspector will display information about the guide.

Applies a timeshift to the guided capture geometry to visualize the guide influence at the given frame.

Displays the guided geometry transformed by the guide (no simulation). The hue represents the guide clusters, the value represents the blend attribute value.

Displays the guide neighbor count as a ramp of colors from red to blue. Black represents no guide neighbors, white are pieces for which use guide neighbor count is disabled.

Turn on the impact data analysis parameters.

The minimum amount of time (in seconds) between recorded impact points. Higher values give fewer impact points and bigger gaps in time.

The minimum amount of impact force for recorded impact points. Higher values only create points for stronger impacts and ignore weaker impacts.

The minimum distance between recorded impact points. Higher values give fewer impact points and bigger gaps in space.

Only create impact points for collisions with this DOP object.

Create an object merge SOP to import the impact points.

Specify the list of attributes to display in the viewport through the inspector.

Specify the font size for the inspector text.

Specify the float precision used to display attribute values.

When an object’s speed has been below its linear and angular speed thresholds for this amount of time, the object is eligible to be deactivated and put to sleep. This can improve performance for simulations where there are some stationary objects.

Distance threshold used by the Bullet engine when determining whether a cached contact point should be discarded. Adjusting this value according to the scene scale may also improve performance, as it influences the margin added to objects' bounding boxes.

Applies a more accurate damping for the drag described by the targetv and airresist point attributes, instead of applying it as an explicit force. This also affects how the targetw and spinresist attributes are applied for angular drag.

Tries to make interpenetrating objects split without adding velocity (to keep objects from explosively flying apart).

Errors when solving positional and velocity constraints can introduce some extra energy to the system. Although this option removes most of the extra energy, it degenerates quality a little bit, in particular for stable stacking.

Split Impulse only applies when objects interpenetrate by more than this distance. This number should be negative (representing less than 0 distance between the objects).

Overrides the Error Reduction Parameter for contact constraints where the penetration distance is within the Penetration Threshold and Split Impulse is enabled.

Specifies which constraint solver Bullet will use to resolve collisions and constraints. Both solvers parallelize the workload, but differ in the strategy they use to do so. Parallel Gauss-Seidel (Islands) will be faster in cases that involve many small “islands” of interacting objects (for example, a large number of small separate book stacks), whereas Parallel Gauss-Seidel (Graph Coloring) should perform better when such “islands” are few and large (such as a huge collapsing building).

Although results obtained with these solvers will generally not be identical, qualitative differences should be minor.

Allows the constraint solver to terminate before performing the full number of Constraint Iterations if it is close enough to the solution. Larger values can increase performance at the cost of accuracy.

Increasing the CFM (constraint force mixing) parameter will make contact constraints softer, and may increase the stability of the simulation. Contact constraints may be violated by an amount proportional to this parameter times the force that is needed to enforce the constraint.

Specifies what proportion of the constraint error for contact constraints will be fixed during the next simulation step. If ERP (error reduction parameter) is set to 0, constrained objects will drift apart as the simulation proceeds. If ERP is set to 1, the solver will attempt to fix all constraint error during the next simulation step (however, this may result in instability in some situations). A value between 0.1 and 0.8 is recommended for most simulations.

Specifies that the constraints should be randomly reordered before each of the Constraint Iterations. This may improve stability, but incurs a minor performance hit.

Specifies that the solver should ensure that changes to an island of interacting objects (including adding, removing, or repositioning objects) do not cause other islands to produce different simulation results, unless those changes cause the objects to interact. Otherwise, the solver only guarantees that resimulating with the exact same input to the solver will produce the same results. Enabling this option may incur a minor performance hit, and may change the simulation results slightly.

Specifies how much memory in megabytes can be consumed by the cache for this simulation. Once this limit is exceeded, old cache entries are deleted.

Solve on simulation start frame.

This flag will re-import the network whenever it is set, allowing a completely animated constraint behavior.

The guiding can be setup outside the RBD Bullet Solver using the RBD Guide Setup SOP.

The simulation geometry packed primitives to be guided.

The reference start frame where guiding attributes will be captured to the simulation geometry.

End frame of the guide animation.

When the End Frame is reached, all pieces will be released from their guides.

Distance beyond which simulation geometry will not acquire a guide. When this value is -1 no maximum is used.

Guide strength.

Multiply the strength based on distance to guide geometry.

Specify the minimum and maximum distance for the Strength Multiplier.

The strength multiplier to use when the distance to the guide piece falls between the Distance min and max.

Add a blend attribute to the simulation pieces which will be multiplied by the global blend value.

Attributes to transfer from the guide piece to the RBD pieces.

Use VEX expressions to modify guiding strength and blend attributes.

When a guided piece has no neighbors within its guide cluster, it will inherit the nearest piece’s guide target.

When finding pieces' neighbors, points are first seeded on the surface of all the objects. There must be enough points for close points to occur to detect close surfaces. This should be scaled down by the square of the geometry size. For example, if your geometry is 10× bigger, you should have 1/100 the points per area.

Specifies the maximum allowed distance when searching for nearby points.

Specifies an upper limit on the number of nearby points that can be inspected. Lower numbers will improve performance, but run the risk that only points from the same piece will be detected rather than points on nearby pieces, causing neighbors to be missed.

Specifies an upper limit on the number of pieces that each seed point can be connected to. This may improve the detection of Adjacent Pieces from Surface Points. However, increasing this value will reduce performance.

When a guided piece has no neighbors within its guide cluster, it will inherit the nearest piece’s guide target.

When the number of connected neighbors within the same guide cluster drops below this number, the piece will become unguided. Pieces with no guided neighbors at rest will be ignored.

Turn on the impact data analysis parameters.

The minimum amount of time (in seconds) between recorded impact points. Higher values give fewer impact points and bigger gaps in time.

The minimum amount of impact force for recorded impact points. Higher values only create points for stronger impacts and ignore weaker impacts.

The minimum distance between recorded impact points. Higher values give fewer impact points and bigger gaps in space.

Only create impact points for collisions with this DOP object.

Create an object merge SOP to import the impact points.

Adds an age point attribute to the objects, which tracks the time since the object was added to the simulation. An age attribute is also added to the constraint primitives. This attribute can be useful for driving custom forces, deleting objects after some time, etc.

Transfer attributes to output simulation points.

Transfers the attributes listed above to the output geometry.

Transfers the attributes listed above to the output proxy geometry.