Simulating Cloth Dynamics


Hair isn't the only system that has the benefit of dynamic motion. Cloth can also benefit from dynamic simulations. The steps for setting up a dynamic cloth simulation are similar to those for hair. First, define the cloth properties and the environmental forces acting on the cloth. Then run the simulation.

Defining cloth properties and forces

To add objects (both cloth and collision objects) to the simulation, click on the Object Properties button in the Object rollout. This opens the Object Properties dialog box, shown in Figure 38.3. Clicking the Add Objects button lets you select scene objects to add to the simulation. Only objects added to the scene are included in the simulation. If an object isn't added, it is ignored. All objects added to the simulation are added to the list at the left. Selected objects in the list can be specified as Inactive, Cloth, or Collision Object. For Cloth and Collision Objects, you can set properties. You also can load and save cloth presets. Cloth presets are saved using the .sti extension.

Tip 

If the cloth tends to pass through objects, then you can increase the Offset value for the collision object.

NEW FEATURE 

The Cling and Stretch % properties are both new in 3ds Max 9.

After all the objects involved in the simulation are included and defined, you can set the simulation range in the Simulation Parameters rollout. The initial state for the object to be draped may be set using the Set Initial State button. The Cloth Forces button, in the Object rollout, opens a simple dialog box where you can select to add additional forces to the simulation. Gravity is added by default, but you can change its value in the Simulation Parameters rollout.

Creating a Cloth simulation

After completing the initial setup, clicking the Simulate button starts the simulation process. The objects are updated in the viewport as each frame is calculated. After every frame is calculated, you can see the entire dynamic simulation by dragging the Time Slider or clicking the Play Animation button. If you want to drape the cloth without running it over several frames, you can use the Simulate Local button. The Simulate Local (damped) button causes the simulation to run local with a large amount of damping, which is useful if the cloth tends to drape too fast. If you want to remove the current simulation because some properties have changed, click the Erase Simulation button, or you can remove all frames after the current simulation frame with the Truncate Simulation button.

Tip 

If the simulation is taking too long to compute, you can cancel the simulation by pressing the Escape button.

image from book
Figure 38.3: The Object Properties dialog box lets you define the properties of cloth and collision objects.

If you need to change a cloth or force property, click Erase Simulation, make the change, and run the simulation again. Simulation motions can be saved as keys with the Create Keys button. Figure 38.4 shows a simple plane object that has been draped over a chair over the course of 100 frames.

image from book
Figure 38.4: After you've defined cloth and force properties, an executed simulation drapes the cloth over a chair.

Viewing cloth tension

For cloth objects created using the Garment Maker modifier, you can view the tension in the cloth using the Tension option in the Simulation Parameters rollout. This option shows the areas of greatest tension in shaded colors. Figure 38.5 shows the tension in the dress draped over the female model from Chapter 19, "Adding and Styling Hair, Fur and Cloth."

image from book
Figure 38.5: You can view the tension for cloth created with the Garment Maker modifier.

NEW FEATURE 

The Tension option for cloth is new to 3ds Max 9.

Tutorial: Draping cloth over a jet

For a larger example of a cloth system, we drape a drop cloth over a jet. To simulate the dynamics of a cloth object, follow these steps:

  1. Open the image from book Sheet over Mig jet.max file from the Chap 38 directory on the DVD. This file includes a Mig-29 jet model created by Viewpoint Datalabs.

  2. Choose the Create image from book Standard Primitives image from book Plane menu command, and drag in the Top viewport to create a plane object that covers the jet. Set the Length and Width Segment values to 100 to make the sufficient resolution for the cloth, and drag the plane object upward in the Front viewport, so it sits above the jet.

  3. With the plane object selected, choose the Modifiers image from book Cloth image from book Cloth menu command to apply the Cloth modifier to the object.

  4. Open the Modifier panel, and click the Object Properties button in the Object rollout to open the Object Properties dialog box. Select the Plane01 object in the left list, and choose the Cloth option. Then select the Silk option from the Presets drop-down list, and set the Thickness to 0.5.

  5. With the Object Properties dialog box still open, click the Add Objects button, select the All button, and click the Add button. With all added properties in the left list selected, choose the Collision Object option and click the OK button to close the dialog box.

  6. In the Simulation Parameters rollout, enable the End Frame option and set the end frame to 100. Then click the Simulate button in the Object rollout. The plane object descends and covers the jet being draped as it falls.

Figure 38.6 shows the sheet draped over the jet.

image from book
Figure 38.6: Computing the dynamics of a cloth object is possible with a cloth system.




3ds Max 9 Bible
3ds Max 9 Bible
ISBN: 0470100893
EAN: 2147483647
Year: 2007
Pages: 383

flylib.com © 2008-2017.
If you may any questions please contact us: flylib@qtcs.net