Primitives

Primitives are the basic 3D geometric shapes that are automatically generated by 3D modeling applications, and which therefore need not be constructed from scratch. A very considerable amount of modeling (perhaps most) begins with primitives, which are then edited and used with other primitives to create more complex objects.

All applications provide spheres, cubes, cylinders (sometimes called disks) and cones. Some provide a wider array. All primitives have parameters that define their size and shape. A sphere necessarily has a center point and a radius, though the application may also provide for defining the sphere by its x,y and z extents--in effect defining the sphere by a cube into which the sphere will fit. Some applications will always generate a primitive using default parameters, which the user must then edit after the object is created. High-end modeling applications typically allow the user to enter parameters numerically before the object is created. In all applications, the dimensions and locations of primitives can be edited either interactively (by dragging lines and points on the screen) or by entering values into a dialog box.

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