In addition curved surfaces also exists. Figure 3 shows some of  solids having curved surfaces.

 

Figure 3. Solids having curved surfaces.

Primitive geometric forms
The shapes of objects are formed from primitive geometric forms . These are

1. Point

1. Line
2. Plane
3. Solid
4. Doubly curved surface and object
5. Warped surface

  The basic 2-D geometric primitives, from which other more complex geometric forms are derived.

• Points,
• Lines,
• Circles, and 
• Arcs