Menu Cells

Dynamics -> Option Setup

The Dynamics -> Option Setup command in the Actor module lets you define how an articulated chain or object responds to dynamic forces and collisions.

To use dynamics, your chain or object must have physical properties assigned to it. For information about assigning physical properties to an object or chain, see the Dynamics -> Physical Properties. For general information on dynamics, see the Dynamics section of the Animating User's Guide.

Procedure

1. Select the chain root or hierarchy parent (for models) of an object.

2. Choose the Dynamics -> Option Setup command.

The Option Simulation Setup dialogue box is displayed.

3. Set the options and parameters.

4. Click Ok All to accept the physical properties for all selected elements, or click Ok to accept physical properties for one element at a time.

Parameters

Root Constraint

Position

Fixes the root of an object or hierarchy in its original (current) position when a simulation is applied. If a chain root is fixed, it does not respond to controls and forces (but the rest of the chain does) or else the whole chain would fall down. This option is selected by default for chains, but not for models.

X, Y, Z: Not currently implemented. Constraint will be met according to any specified axes.
Induce acc. (acceleration) causes the chain to be dynamically affected by any movement from anything to which it is attached (either its parent or a constraint). If this option is not selected, the chain follows like a branch of a hierarchy, not acting with its parent's movements.

Orientation

Constrains the first joint of a chain to the root's orientation. If not selected, the joint rotates in response to current forces.

X, Y, Z constraint can be set according to any of the root axes. However, if only one axis is left free to rotate, it should not be the
y-axis because it can rotate only from -90 to 90 degrees. This limitation should be considered when building some objects.
Induce acc. (acceleration) functions in the same way as the positional constraint previously described except that the acceleration passed or induced is the rotational acceleration.

Dynamic Constraints

Gravity

Applies gravity to the object.

Collisions

Activates collision detection.

Object seen as: The selected object can be defined with the geometry of any of the following for collisions:
- Actual shape
- Bounding box
- Bounding sphere

Note:: Obstacles participating in the collision need to be defined as such (see Collisions -> Select ( ) Obstacle). For more general information about collisions, see the Creating Obstacles for Collisions section of the Animating User's Guide.

Wind/Fan

Detects wind or a fan assigned to the selected model.

Object seen as: the selected object can be replaced with the geometry of one of the following for Wind/Fan:
- Actual shape: The wind acts on the actual shape (facets) of the objects. Some combinations of wind/fan vs. object types are currently unavailable: wind and fan on patches (bounding box is used), and fans on polygon meshes because holes must be considered (bounding box is used).
- Bounding box: The wind acts on the bounding box around the objects. All joint models and hierarchy nodes are affected by the wind/fan even if they do not have physical properties. Only the geometry of an object is necessary.

Maximum Subdivision for Fans

Allows you to limit the number of facet subdivisions performed to find the effect of a fan on an object's bounding box or shape. Higher values (values range from 1 to 5) are more precise, but take longer to calculate.

Dynamic Geometry

Update Before Each Frame

This option is useful when you have animated the position of sub-parts of a joint model or submodels in a hierarchy animated with dynamics. When set, the object's centre of mass and inertia are recomputed before each frame so that the simulation can take their new values into account. This option must be selected when you want to animate the scaling of a chain during the simulation.

Key

Creates a keyframe at the current frame position for the root positional constraint. The resulting function curve, which can be seen by selecting the FcrvSelect -> Dynamics -> Root Position Constraint command in the Motion module, has two possible values: either 0 or 1 for the unconstrained or constrained state, respectively.

Restore

Resets all parameters to their default values.

Ok All

Accepts the new parameter settings and copies them to every valid element currently selected.

Ok

Accepts the new parameter settings for each valid element selected, one at a time.

Cancel

Exits the dialogue box.

SOFTIMAGE 3D Reference - 18 APR 1996