This scheme is based on the principle that two primitives can be combined to produce a new solid model. This method is also known as ‘Building Block’ method. The scheme uses the Union, Intersection, and Subtraction techniques to create three-dimensional models, which are based on the Boolean operation. The steps involved in generating a solid model are:

1. Select the primitives from a library
2. Go through the scaling, dimension modification, and any other transformations.
3. Combine the primitives to create the desired solid model.

Since CSG method uses solid primitives, internal details of the object are automatically contained in the model. The model can be sectioned to reveal internal details and can be used for calculating mass, volume, moment of inertia, etc.

New solid models can be created from the primitives or other solid models by the boolean following operations:

• Union (U): Two solids are joined and the common volume of one of the primitives is neglected in the resulting solid.
• Subtraction or Difference (-): One solid is subtracted from the other and the resultant solid retains only the uncut portion of the solid.
• Intersection (П): When two solids are combined, the resultant solid represents the common volume of the two solids.

The most common primitive solids found in a CAD program are: Block, Cylinder, Cone, Sphere, Wedge, and Torus.

A primitive can typically be described by a procedure which accepts some number of parameters; for example, a sphere may be described by the coordinates of its center point, along with a radius value. These primitives can be combined into compound objects using operations like these: Combining these elementary operations, it is possible to build up objects with high complexity starting from simple ones.