3ds Max 2012 Bible - Kelly L. Murdock [98]
• Reference Coordinate System: Defines the coordinate system about which the transformations take place.
• Transform Center settings: The Pivot Point Center, the Selection Center, and the Transform Coordinate Center. These settings specify the center about which the transformations take place.
• Axis Constraint settings: Allow the transformation to happen using only one axis or plane. These buttons are on the Axis Constraints toolbar.
Understanding reference coordinate systems
Max supports several reference coordinate systems based on the UCS, and knowing which reference coordinate system you are working with as you transform an object is important. Using the wrong reference coordinate system can produce unexpected transformations.
Within the viewports, the UCS coordinates are displayed as a set of coordinates in the lower-left corner of the viewport, and the Transform Gizmo is oriented with respect to the reference coordinate system.
To understand the concept of reference coordinate systems, imagine that you're visiting the Grand Canyon and are standing precariously on the edge of a lookout. To nervous onlookers calling the park rangers, the description of your position varies from viewpoint to viewpoint. A person standing by you would say you are next to him. A person on the other side of the canyon would say that you're across from her. A person at the floor of the canyon would say you're above him. And a person in an airplane would describe you as being on the east side of the canyon. Each person has a different viewpoint of you (the object), even though you have not moved.
Max recognizes the following reference coordinate systems:
• View Coordinate System: A reference coordinate system based on the viewports; X points right, Y points up, and Z points out of the screen (toward you). The views are fixed, making this perhaps the most intuitive coordinate system to work with.
• Screen Coordinate System: Identical to the View Coordinate System, except the active viewport determines the coordinate system axes, whereas the inactive viewports show the axes as defined by the active viewport.
• World Coordinate System: Specifies X pointing to the right, Z pointing up, and Y pointing into the screen (away from you). The coordinate axes remain fixed regardless of any transformations applied to an object. For Max, this system matches the UCS.
• Parent Coordinate System: Uses the reference coordinate system applied to a linked object's parent and maintains consistency between hierarchical transformations. If an object doesn't have a parent, then the world is its parent and the system works the same as the World Coordinate System.
• Local Coordinate System: Sets the coordinate system based on the selected object. The axes are located at the pivot point for the object. You can reorient and move the pivot point using the Pivot button in the Hierarchy panel.
• Gimbal Coordinate System: Provides interactive feedback for objects using the Euler XYZ controller. If the object doesn't use the Euler XYZ controller, then this coordinate system works just like the World Coordinate System.
• Grid Coordinate System: Uses the coordinate system for the active grid.
• Working Coordinate System: Lets you transform the selected object about the scene's Working Pivot as defined in the Hierarchy panel.
• Pick Coordinate System: Lets you select an object about which to transform. The Coordinate System list keeps the last four picked objects as coordinate system options.
All transforms occur relative to the current reference coordinate system as selected in the Referenced Coordinate System drop-down list found on the main toolbar.
Each of the three basic transforms can have a different coordinate system specified, or you can set it to change uniformly when a new coordinate system is selected. To do this, open the General panel in the Preference Settings dialog box and select the Constant option in the Reference Coordinate System section.
Using a transform center
All transforms are done about a