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Using Custom and Generic units

To define a Custom units system, modify the fields under the Custom option, including a units label and its equivalence to known units. The final option is to use the default Generic units. Generic units relate distances to each other, but the numbers themselves are irrelevant. You also can set lighting units to use American or International standards. Lighting units are used to define Photometric lights.

At the top of the Units Setup dialog box is the System Unit Setup button. This button opens the System Unit Scale dialog box, also shown in Figure 4.1. This dialog box enables you to define the measurement system used by Max. Options include Inches, Feet, Miles, Millimeters, Centimeters, Meters, and Kilometers.

For example, when using Max to create models that are to be used in the Unreal game editor, you can use the Custom option to define a unit called the Unreal Foot unit that sets 1 Uft equal to 16 units, which matches the units in the Unreal editor just fine.

A multiplier field allows you to alter the value of each unit. The Respect System Units in Files toggle presents a dialog box whenever a file with a different system units setting is encountered. If this option is disabled, all new objects are automatically converted to the current units system.

The Origin control helps you determine the accuracy of an object as it is moved away from the scene origin. If you know how far objects will be located from the origin, then entering that value tells you the Resulting Accuracy. You can use this feature to determine the accuracy of your parameters. Objects farther from the origin have a lower accuracy.

Caution

Be cautious when working with objects that are positioned a long way from the scene origin. The farther an object is from the origin, the lower its accuracy and the less precisely you can move it. If you are having trouble precisely positioning an object (in particular, an object that has been imported from an external file), check the object's distance from the origin. Moving it closer to the origin should help resolve the problem. •

Handling mismatched units

Imagine designing a new ski resort layout. For such a project, you'd want to probably use kilometers as the file units. If your next project is to design a custom body design on a race car, then you'll want to use meters as the new units. If you need to reopen the ski resort project while your units are set to meters, then you'll get a File Load: Units Mismatch dialog box, shown in Figure 4.2.

This dialog box reminds you that the units specified in the file that you are opening don't match the current units setting. This also can happen when trying to merge in an object with a different units setting. The dialog box lists the units used in both the file and the system and offers two options. The Rescale the File Objects to the System Unit Scale option changes the units in the file to match the current system units setting. The second option changes the system units to match the file unit settings.

Tip

If you rescale the file object to match the system file units setting, then the objects will either appear tiny or huge in the current scene. Use the Zoom Extents All button to see the rescaled objects in the viewport. •

FIGURE 4.2

The Units Mismatch dialog box lets you synch up units between the current file and the system settings.

Rescaling world units

If you discover halfway through your scene that you're working with the wrong units, you can use the Rescale World Units utility to scale up the entire scene or just selected objects. To access this utility, click the Utilities panel and then the More button. In the utilities list, select the Rescale World Units utility and click OK.

The Rescale World Units dialog box has a Scale Factor value, which is the value by which the scene or objects are increased or decreased. If your world was created using millimeter units and you need to work in meters,