3ds Max 2012 Bible - Kelly L. Murdock [466]
Constraints can be made Breakable, and you can set the Max Force and/or Torque required to break the constraint. Once a constraint is broken, it no longer has any affect on the simulation.
Within the Connection rollout, you can alter the objects that are used for the Parent and Child objects. Additional rollouts define the available translation, swing, twist, and spring properties for each type of constraint. For each, you can set the constraint to be Locked, Limited, or Free about each axis. If the Limited option is enabled, then you can set the limits using the values such as Limit Radius, Bounce, Spring, and Damping.
Although you can move the constraint helper to wherever it needs to be, it is often easier to define the constraint's location by positioning the object's pivot. In the Advanced rollout are buttons for moving the constraint helper to the parent or child's pivot location.
Tutorial: Opening a door
Each of the constraints enables different types of motion and some situations require multiple constraints, such as the hinge on a door.
To use constraints to restrict the motion of a door, follow these steps:
1. Open the Door with a hinge.max file from the Chap 43 directory on the CD.
This file includes a simple door between two walls.
2. Open the MassFX toolbar. Then select all the objects except the floor and click the Set Selected to Dynamic Rigid Body button. Select the floor object and set it to Static.
3. Select the far wall object and then the door object and click the Create Hinge Constraint from the MassFX toolbar. Then drag in the viewport to set the constraint's size. Move the constraint so it is positioned at the point between the wall and the door and rotate it so it allows the door to swing away from the ball.
4. Select both wall objects and choose the Create Rigid Constraint option from the MassFX toolbar. This prevents the walls from moving.
Caution
Static objects cannot be used as a parent or child for a constraint. •
5. Select the ball object and set its Density to 20, the X Initial Velocity value to -1, and the Speed value to 5000. This should be enough to give the door a good kick.
6. Click the Start Simulation button in the MassFX toolbar.
Figure 43.6 shows the door flying open.
FIGURE 43.6
Using the hinge constraint controls the motion of this door.
Capturing the Simulation Motion as Keys
Once you're happy with the motion created by the simulation, you can capture the motion as keys using the Bake command. There is a Bake button in the Rigid Body Properties rollout of the Edit panel in the MassFX Tools dialog box. There are also several different bake options in the Tools panel including options to Bake All, Bake Selected, Unbake All, and Unbake Selected.
Once the motion is baked, the keys for each object in the simulation show up on the Track Bar and the animation can be manipulated and edited using the animation tools and the Track View.
The Tools panel also includes another helpful button. The Capture Transforms button causes the current state of the selected objects to be reset as its new initial position. If the Reset Simulation button is then used, this new initial position is used instead of the object's original location. This is great because it give you a chance to let the objects settle at the start simulation and then reset them in this location before starting the simulation.
Within the Utilities rollout of the Tools panel, the Explore Scene button opens the Scene Explorer where it shows all the objects included in the simulation and their respective simulation properties including SimType, SimMode, SimEnabled, and SimBaked. From this scene, you can quickly enable and disable multiple objects or change their object type.
The Validate Scene button runs a quick check on the simulation looking for potential problems that might be encountered when the scene is exported, as shown in Figure 43.7. It looks