3ds Max 2012 Bible - Kelly L. Murdock [465]
The modifier also includes an option for changing the Center of Mass location and for moving and manipulating the collision mesh's transform.
Displaying interactions
The Display panel of the MassFX Tools dialog box has a number of options that you turn on and off to see the simulation properties. The Display Physical Meshes option shows the collision mesh for all objects or only for the selected objects if the Selected Objects Only option is enabled.
If you turn on the Enable Visualizer option, then a whole range of different properties are made visible as the simulation proceeds including arrows showing object speed, contact points between objects and collision meshes.
Tutorial: Knocking over milk cans
You can add motion to the simulation objects in two ways. One is to use the initial motion values in the Advanced rollout of the Edit panel of the MassFX Tools dialog box. The other is to set an object as a Kinematic object that is animated using standard keyframes and then switched to a Dynamic object at a given frame with the Until Frame option in the Rigid Body Properties rollout of the MassFX Tools dialog box.
To animate the milk can tipping carnival game, follow these steps:
1. Open the Tipping milk cans.max file from the Chap 43 directory on the CD.
This file includes several milk cans positioned on a cylinder along with three balls.
2. Right-click the main toolbar, and select MassFX Toolbar. Then select all the milk cans located above the cylinder, and click the Set Selected as Dynamic Rigid Body button. Then click the Display MassFX Tools Dialog button on the MassFX toolbar and in the Edit panel, set the Density value to 10 for all the milk cans.
4. Select the cylinder and the floor objects, and click the Set Selected as Static Rigid Body button.
5. Select the smallest ball object, and click the Set Selected as Dynamic Rigid Body button. Then open the Advanced rollout and set the X Initial Velocity value to -1 and the Speed value to 2500. Then click the Start Simulation button in the MassFX toolbar, and notice how the first ball falls a little short. Click the Reset Simulation button in the MassFX toolbar.
6. Locate and click the Time Configuration button beneath the Play button at the bottom of the interface and in the Time Configuration dialog box, set the End Time to 300.
7. Select the second ball object, and click the Set Selected as Kinematic Rigid Body button. Then enable the Until Frame option in the Rigid Body Properties rollout to 100. Then set the Density to 3, the X Initial Velocity value to -1 and the Speed value to 2500. Then click the Start Simulation button in the MassFX toolbar, and notice how the second ball knocks them all down.
Figure 43.5 shows the large ball striking the milk cans.
FIGURE 43.5
Kinematic objects can be made to start at a later frame.
Using Constraints
Constraints are ways to limit the amount of motion that an object can do. Using constraints can help control objects in the scene as they interact with other objects. Perhaps the simplest constraint isn't a constraint at all. If you set an object to be Static, it won't move.
Other constraints found in the MassFX toolbar include Rigid Constraint, Slide Constraint, Hinge Constraint, Twist Constraint, Universal Constraint, and Ball & Socket Constraint. To apply a constraint, you need two objects, and they both must be selected. The first object you select becomes the parent object and the second the child.
Note
You can also select a single object and apply a constraint and then pick the parent object later using the button in the Modify panel. •
After the constraint is selected, a helper object titled UConstraint is added to the scene, and you can drag out the helper object to show the range of the