Dynamic Item

Toggles dynamics on and off for the item.

When enabled, Modo applies dynamics to the item when a simulation is run or cached. When disabled, the dynamic properties are ignored.

Dynamic items can be defined as one of three types:

• Rigid: The item is treated as a solid object with a fixed, unchanging volume.

• Softbody: A soft body deforms during a collision or when a force is applied.

• Curves: Curves are used for items that consist of one or more curved strands, such as hair or wires.

Selecting each option hides/reveals different attributes in the Properties panel.

The associated item does not move during a simulation (even if animated), acting strictly as a collision object.

When Static is disabled, two options become available in State.

State is enabled when an item is not static.

• Dynamic: These are collision items controlled exclusively by dynamics. They can also be affected by constraints, forces, and falloffs.

This is automatically assigned when an object is defined as an Active Rigid Body.

Note:  This should be set for animating fur guides.

• Kinematic: An animated collision object that is controlled by keyframe information. Kinematic objects are unaffected by forces, such as gravity or falloffs.

This is automatically assigned when an object is defined as a Kinematic Rigid Body.

Collision: Rigid

This is the shape to calculate collision contacts between dynamic objects. In general, you should choose the simplest shape that produces satisfactory results.

The default collision shape is set to Hull, which generally balances accuracy with calculation speed.

• Box: A rectangular box defined by the bounding box of the geometry's maximum extents.

• Sphere: A sphere that is sized to encompass all the geometry of the object.

• Hull: This collision shape creates the smallest convex volume that encompasses all the points in this mesh (imagine the mesh enveloped in shrink-wrap).

The Hull collision type does not support holes or indentations in the object. Although it only approximates the item's shape, it provides very fast collision detection on complex shaped objects.

• Multi Hull: The default collision option, Multi Hull generates a separate convex hull for each polygon island in the mesh. These are then treated as a single, compound dynamic item.

• Mesh: Uses the mesh of the object for calculating collisions. For subdivision surface models, the actual frozen Sub-D cage is used.

Note:  Avoid this option on Dynamic Rigid Bodies (it is fine for Static and Kinematic ones). Otherwise, performance and simulation stability can suffer negatively.

• Convex Decomposition: Creates multiple hulls (see above) and connects them together. This works to better approximate the actual shape of the geometry, but can be costly to initially compute with complex shapes.

• Plane: Generates an infinite ground plane collision shape, originating from the center of the associated geometry's bounding box (not on the item's actual center position).

Disable this option to remove the object from collision calculations.

This is the collision response when the object hits another dynamic object.

A value of 0% means the object doesn't bounce or inherit energy from the other dynamic object.

A value of 100% means the object inherits all of the energy from the contact object.

Values above 100% produce rubber ball-like effects where objects impart more energy from contacts.

The amount an object slides against another object.

A value of 0 offers no resistance. A value of 1 stops the object from sliding.

When two dynamic elements collide and they both have a non-zero Stickiness, they attach to each other at the collision point.

The higher the Stickiness value, the stronger the bond between the elements. Lower values allow stuck elements to be broken more easily.

The amount that a soft body slides against another dynamic object.

A value of 0 offers no resistance. A value of 1 stops the object from sliding.

When two dynamic elements collide and they both have a non-zero Stickiness, they attach to each other at the collision point.

The higher the Stickiness value, the stronger the bond between the elements.

Disable this option to remove the object from collision calculations (enabled by default).

This is the collision response when the curve capsule colliders hit another dynamic object.

A value of 0% means the object doesn't bounce or inherit energy from the other dynamic object.

A value of 100% means the object inherits all of the energy from the contact object.

Values above 100% produce rubber ball-like effects where objects impart more energy from contacts.

The amount an object slides against another object.

A value of 0 offers no resistance. A value of 1 stops the object from sliding.

• World Density: Calculate the mass by multiplying the calculated volume of the dynamic item by the Global Density value defined on the Dynamics Solver item.

• Local Density: Mass is calculated by multiplying the computed volume by this value.

• Local Mass: Set the mass manually.

The measure of the amount of matter in any given volume. If the Mass Source option is set to Local Density, this value is used to calculate the mass.

Prior to the Wake On event, items can be keyframe-animated and the object is handed off to dynamics for simulation when the Wake On Value threshold is reached.

The values defined in the Impulse channels are applied when the object wakes up.

• Start: The object begins the dynamic simulation awake and fully active at the beginning of the scene.

• Collision Velocity: The object wakes up when it collides with a passive or active object.

• Collision Force: The object wakes up when it collides with a passive or dynamic object.

• Velocity: The object wakes up when a certain velocity is reached. Different from Collision Velocity, this velocity is determined by keyframe animated motion.

• force: The object wakes up when the force applied by a force item reaches the threshold.

Note:  Use the Wake On Value to set a threshold for the Collision Velocity, Collision Force, Velocity, or force.

• Trigger: The object wakes up when the keyframe-able channel, reWakeOnValue, is not zero.

This has good use with conditional nodes in rigging.

• Frame: The object wakes up when a specific frame number is reached.

• Time: The object wakes up when a specific time has been reached, regardless of frame rate.

This is the threshold that must be reached in order to wake up the object, depending on the Wake On option selected.

This option determines the state that causes the Impulse value to be applied to the dynamic item.

• Off: No impulse value is applied to the object.

• On Wake: The impulse values are applied when the item wakes up, as determined by the Sleep settings.

• Continuous: The impulse value is applied to the object continually at every step in the evaluation.

A directional force that is applied to the object when it wakes up.

This is useful when a keyframed object is handed off to dynamics, imparting direction and velocity to the object. Without Impulse the velocity would drop, as dynamics has no awareness of the object's velocity prior to waking up.

The position the Impulse is applied from, affecting the object's trajectory.

This is a force that acts upon the motion of objects to slow them down over time.

A small value here can benefit object stability, since it helps objects come to rest.

Same as Linear Damping, but applies to the rotation of the object.

Note:  Angular Damping is not available for Soft Body objects.

When under the influence of the dynamics system, animated dynamic items ignore their user-assigned kinematic (keyframed) motion. Instead, they act under the forces applied to them, and any collisions encountered.

Follow Linear applies an amount of force to an item to seek its kinematic position. The setting allows you to influence a dynamic solution by adding keyframes to the item and increasing the Follow Linear force value.

When enabled, the item never gets deactivated due to no motion.

When disabled, the item is disabled when it meets the defined linear and angular thresholds defined in the solver item (or overridden here).

Enable this function to put dynamic objects to sleep once they reach a defined upper threshold value, overriding the global value found in the Dynamics Solver.

This behaves opposite to the Wake On settings; once an object has been below the threshold for the defined length of time, it is put to sleep.

The motion threshold value when Override Linear Threshold is enabled.

Enable this function to put dynamic objects to sleep once they reach a defined upper threshold value, overriding the global value found in the Dynamics Solver.

This behaves opposite to the Wake On settings; once an object has been below the threshold for the defined length of time, it is put to sleep.

Enable this to determine interactions between dynamic items and particles.

Note:  This is necessary for Wake On actions that are triggered by particle collisions.

This adds a random factor to the direction in which particles bounce off the item.

At 100% it can bounce up to 90 degrees away from the collision normal.

The shape of a Soft Body is determined by virtual springs, evaluated between the vertices in the mesh. These springs help an object maintain its shape by applying a rotational force to maintain the continuity of the surface.

Stiffness can be reduced all the way to 0, creating a very soft and saggy fabric type.

These springs follow along the lines of the mesh (along the polygon edges). This value determines how resistant the springs are to the applied forces when deforming, due to forces such as gravity or turbulence.

These springs are generated to add extra connections to the inside of a polygon face (quad polygons forming an x shape). They help to prevent the polygon from collapsing in on itself.

Enable this option to fix issues with the surface intersecting itself.

This exerts a force upon the overall volume of an item, similar to how pressure reacts on an object in the real world.

Increasing values add overall volume, inflating the item.

Decreasing (negative) values reduce its volume, deflating the item.

Note:  This option requires that the target mesh be completely watertight (no seams).

This option works with the Pressure option. You can use it to preserve the volume of the Soft Body. For example, if you crush one part of a balloon, the rest of it expands so that it still contains the same volume of air.

Determines the loss of energy on a surface that is in motion (say, for jiggling-type of effects).

This option multiplies the force applied by the surface normal.

When enabled, forces coming from the back-side of a single-sided object are not applied.

If a goal map is specified, this option acts as a multiplier on the map values.

When enabled, the resulting capsules generated with dynamics, match the size defined, even when they are modulated with a curve width gradient.

Controls the rigidity of the curves in a simulation, and how multiple curves within a single item layer are treated.

• Off: All curves are treated individually as soft, deforming elements.

• Per Curve: All curves are treated individually as rigid, non-deforming elements.

• Item: All curves are treated as a combined (single) rigid, non-deforming element.

When the Use Render Radius option is disabled, this option determines the collision size for the resulting capsule collision elements.

When enabled, it automatically pins the first vertex of a curve. Pinned vertices remain fixed to their position within the mesh layer, moving only when the layer is animated or its geometry is deformed.

This option is mainly used for simulating hair guides, to keep them connected to their character.

The collision capsules that are generated for a simulation are generated between each vertex, creating a chain of collision objects. The first segment begins at the base position of the curve. For pinned curves the first segment is always disabled for collision.

The Disable Segment Collision Start value allows you to disable collision on additional segments. For example, if there is a curve with 8 segments pinned to a character, and this value is set to 3, then only the last 5 segments of the curve would be considered for collision.

Allows you to fix vertices along the curve, meaning they won't move or be affected by the dynamics.

This is done by the addition of a Pick Map.

Once added, the Pick Map appears in the Pin Map dropdown list. If you select a Pick Map, the targeted vertices aren't affected by curve dynamics.

Limits the amount of bending allowed between curve segments, this is very useful for fur guide simulations so that the fur doesn't go crazy during fast motions.

When working with compound rigid bodies, the compound glue option is used to connect the items within the same compound group. When the amount of force exceeds the designated amount, the items break apart from the compound and are treated as individual items during a simulation.

Note:  Only items that are physically touching each other (sharing some geometry) are glued together, elements floating away from the compound group are not affected by the Compound Glue value.