In order for any item in modo to be considered in a Dynamics simulation, it must first be converted to a dynamic item. This is done by tagging it appropriately. The controls to apply the tagging are found in the toolbox of the 'Setup' interface under the 'Dynamics' subtab. The options include creating either a 'Passive Rigid Body', an 'Active Rigid Body', a 'Soft Body or a 'Compound Rigid Body'. To apply the tag, simply select the item while in 'Items' mode and invoke the appropriate command. What tag is selected is dependent on the desired results, with each Body type explained below. Once the appropriate tag is applied, an additional property sub form called 'Dynamic' is added to the items Properties panel with a series of attributes relating to the settings of the object and the dynamics simulation. While the default values will work in some cases, users will likely wish to modify the defaults to settings more appropriate for their intended purpose.
To make an object un-dynamic, removing it completely from the Dynamics calculations, users simply need to select the target item and invoke the menu bar command "Dynamics > Make Un-dynamic" eliminating any dynamics information from the object. To temporarily disable the object from the dynamics simulation, toggle the 'Enable' option.
Enable: Toggles dynamics on and off for the item. When enabled, modo will calculate dynamics for the item when a simulation is run or cached. When disabled, the dynamic properties will be ignored.
Preset:
Type: Dynamic items can be one of three types-
Dynamic- A collision object with a density greater than 0, that is controlled exclusively by Dynamics. It can also be affected by Constraints, Forces, and Falloffs. This is the option automatically designated when an object is defined as an 'Active Rigid Body'.
Kinematic- A collision object that is either static or controlled by user created keyframes. Kinematic objects are unaffected by Forces, such as gravity or Falloffs. This is the option automatically designated when an object is defined as a 'Passive Rigid Body'.
Soft Body- Soft Bodies are are a special type of collision object that deform when a collision is calculated, or a Force is applied. When the 'Soft Body' option is selected additional options are added related specifically to Soft Body for 'Stiffness' and 'Number of Clusters'.
Stiffness: Determines how soft or rigid the resulting surface is. The default of 0.5 makes a fairly rigid, almost rubber-like surface. Stiffness can be reduced all the way to 0 creating a very saggy fabric type of result.
Number of Clusters: This is basically the resolution of the Soft Body collision geometry. Â The higher the number the more accurate the soft body will look. This does nothing to affect the ability of the Soft Body to actually collide, but rather controls the size of the internally created collision object used to test collisions. Setting this number to 0 will turn off all collisions for the Soft Body, while setting it to -1 will try to create a collision object per-face. Regardless of the setting, the maximum number of clusters is 8192. Note that increasing the number of clusters can significantly increase simulation time.
Goal Map: The 'Goal Map' is a Vertex Map that applies to Soft Body items and controls how much it retains its initial undeformed shape. It can also be looked at as a stiffness control. Weight Map values of 1.0 will retain the original undeformed position, while values lower than 1 will apply an appropriate spring force attempting to retain the initial shape.
Collision--
Collision Shape: This setting defines the shape that will be used to calculate collisions between dynamic objects. Generally users will want to 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- The default collision option 'Hull' creates the smallest convex volume that encompasses all the points in this mesh. To visualize it, imagine the mesh enveloped in shrink-wrap. The 'Hull' collision type does not support holes or indentations in the object. While only approximating the items shape, it will provide very fast collision detection on complex shaped objects.
Mesh- Uses the actual mesh of the object for calculating collisions. For Subdivision Surfaces models, the actual frozen SubD cage is used. This should be used only if you need the total accuracy as performance can suffer with its use.
Convex Decomposition- The 'Convex Decomposition' creates multiple Hulls (described above) and connects them together. This works to better approximate the actual shape of the geoemtry but can be costly to initally compute on complex shapes.
Do Collisions: Users can disable this option so that the object is not taken in to account for collision calculations (enabled by default).
Bounce: This is the collision response when this object hits another dynamic object. A value of 0.0 means the object will not bounce or impart energy onto objects it hits. A value if 1.0 would conserve all of the objects energy.
Friction: The amount an object will slide against another object. A value of 0.0 would offer no resistance, while a value of 1.0 would keep the object from sliding entirely.
Margin: The 'Margin' value helps the bullet engine to determine collisions with moving items. If the value is negative, Dynamics move the collision vertices of the item inward along their averaged normal and then extends the margin by the same amount which should result in a fairly tight fitting shape. If it is positive, Dynamics simply extends the collision vertices of the geometry outward by that amount
Mass--
Mass Source: When the 'Mass Source' is set as 'World Density', the mass of an object is calculated by multiplying the calculated volume of the dynamic item by the 'Global Density' value defined on the Dynamics Solver item. Users can override that value by setting the 'Mass Source' to 'Local Density' or 'Local Mass' and expressly setting a value.
Density: Density is the measure of the amount of matter in any given volume. If the 'Mass Source' option is set to 'Local Density', this is the density value that will be used. The mass of the object will be determined by multiplying the computed volume by this value.
Mass: Mass is the properties of an object that give it bulk and weight. It is essentially a different way of determining density. If 'Mass Source' is set to 'Local Mass', this is the value that will be used for simulations.
Sleep--
Wake On: Normally objects are awake (active) when any dynamic simulation starts and the object begins to react immediately. Users can change this behavior delaying when individual objects wake up and become active. Prior to the 'Wake On' event, items can be keyframe animated and the object will be handed off to Dynamics for simulation when the certain 'Wake On Value' threshold is achieved. The values defined in the 'Impulse' channels are applied when the object wakes up.
Start- Object begins the dynamic simulation awake and fully active at the beginning of the scene.
Collision Velocity- Object wakes up when either another passive or active object collides with it. Users can use the 'Wake On Value' to set a collision velocity threshold necessary to wake up the object.
Collision Force- Object wakes up when either another passive or dynamic object collides with it. Users can use the 'Wake On Value' to set a collision force threshold necessary to wake up the object.
Velocity- Object wakes up when a certain velocity is reached. Different from 'Collision Velocity', this velocity is determined by keyframe animated motion. Users can use the 'Wake On Value' to set the velocity threshold necessary to wake up the object.
Trigger- Object wakes up when the keyframeable channel, 'reWakeOnValue' is non zero (any number but zero). This has good use with conditional nodes in rigging.
Frame- Object wakes up when a specific frame number is reached.
Time- Object Wakes Up when a specific time has been reached, regardless of frame-rate.
Wake On Value: Depending on the 'Wake On' option selected, users can set a lower threshold that must be reached in order to wake up the object.
Impulse--
Impulse X/Y/Z: A directional force that is applied to the object when it wakes up. Useful when a keyframed object is handed off to Dynamics, imparting direction and velocity to the object, which would otherwise just drop without it as Dynamics has no awareness of the objects velocity prior to waking up.
Impulse Position X/Y/Z: Position the above impulse is applied from affecting the objects trajectory.
Torque Impulse X/Y/Z: A rotational force that is applied to the object when it wakes up. Useful when a keyframed object is handed off to Dynamics, imparting rotation to the object, which would otherwise not spin without it as Dynamics has no awareness of the objects motion prior to waking up.
Force--
Linear Damping: This is a force that acts upon the motion of objects, acting to slow them down over time. A small value here can benefit object stability since it helps objects come to rest.
Angular Damping: Same as 'Linear Damping' but applies to the rotation of the object.
Glue Strength: The 'Glue Strength' applies to 'Compound Rigid Bodies' and determines the amount of glue between dynamic items or how strongly they adhere opposing faces together. When the Strength threshold is exceeded, the items will break apart.
Normal Modulation: When the 'Normal Modulation' option is enabled, any forces applied to the Soft Body element will be multiplied by the dot product between the soft bodies vertex normal and the direction of the force, more closely mimicking the way a piece of paper or cloth would interact with the wind. When disabled Soft Body Forces will act as they did in initial release of modo 701.
Front Only: Forces by default are applied to both sides of a Soft Body element. When the 'Front Only' option is enabled all forces will only be applied to the front facing normal direction of the Soft Body elements.
Deactivation--
Deactivation Time: The 'Deactivation Time' defines how long a dynamic object must be below the Linear or Angular threshold before being put to sleep. The default value is one second, so depending on the frame rate of the scene, the default value will change; generally it is 24 frames.
Override Linear Threshold: Users can 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. Essentially the opposite of the 'Wake On' settings, once an object has been below the threshold for the defined length of time, Dynamics puts it to sleep.
Linear Threshold: This is the motion threshold value when 'Override Linear Threshold' is enabled.
Override Angular Threshold: Users can 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. Essentially the opposite of the 'Wake On' settings, once an object has been below the threshold for the defined length of time, Dynamics puts it to sleep.
Angular Threshold: This is the rotation threshold value when 'Override Angular Threshold' is enabled.
Particles--
Wake On Particles: The 'Wake on Particles' can be enabled to determine interactions between dynamic items and particles. Necessary for 'Wake On' actions that are triggered by particle collisions.
Particle Collision Roughness: Adds a random factor to the direction particles bounce of this item. At 100% it can bounce up to 90 degrees away from the collision normal.
Particle Collision Stickiness: The distance at which particles will try to stick to the surface of this item.
