Primitive Instancing:

In primitive instancing, the modelling system described a set of primitive 3D solid shapes which are relevant to the application area. Primitive instances are same to parameterized solid objects. A parameterized primitive may be thought of as describing a family of parts whose members vary in a few parameters, significant CAD concept known as Group Technology. Primitive instancing is frequently used for relatively 'complex objects', such as gears and bolts, that are tiresome to define in terms of Boolean combinations of simpler objects, yet are readily characterized by a few high-level parameters. This is easier to sew and create unambiguous and unique solids. The major disadvantage is obviously the limited domain of objects that may be handled.

In primitive instancing, no provisions are built up for combining objects to form a new higher-level object, by using the regularized Boolean set operations. Therefore, the only way to makes a new kind of object is to write the code that described it. Likewise, the routines that draw the objects or make their mass properties should be written individually for each primitive. The major disadvantage is clearly the restricted domain of objects that may be handled. The method is limited to the primitives predefined in the system and they are quite limited.