十二、shapes

1. The control points are attributes on the shape which are usually arrays of points. Control points become interactive, i.e. they can be selected and manipulated, by associating the control point attributes with a component.Components are objects (MObject’s) which contain two pieces of information, the type of component and the index values or range.

2. The purpose of a user-defined shape and all the classes associated with shapes is to "wrap" an arbitrary geometry type that you defined as a DAG node (and a DG node), or as data passed through the DG.

The class MPxSurfaceShape lets you write shapes using the Maya API.

The major difference between MPxSurfaceShape and MPxNode is the addition of component handling, drawing, and selection functions. The overridable functions have been split into two classes, the DG node functionality is in MPxSurfaceShape and the drawing and select functions are in MPxSurfaceShapeUI.

3. The following lists the proxy classes you will be deriving from:

• MPxSurfaceShape or MPxComponentShape (required): the DG node class
• MPxSurfaceShapeUI (required): drawing and selection
• MPxGeometryIterator (optional): iterator for components (optional)
• MPxGeometryData (optional): used to pass geometry through the DG