7. Constructive Solid Geometry - Building blocks put together

Constructive solid geometry or CSG allows us to play around with our primitives and build complex objects. CSG supports union, intersection
and difference of two or more objects. Essentially a CSG tree gets built for each CSG object with the nodes being the primitives or CSG subtrees
themselves. The various CSG operations are explained below.

1. Union -
   An union CSG object C (where C = A union B) will contain all the points which belong to A OR B. A sample union specification is shown below -

   Figure 7

   union
   {
     object
      {
       surface { ... }
       sphere { ... }
       transform
      }
     object
      {
       surface { ... }
       cylinder { ... }
       transform
      }
   }
   

   The union can be of two primitives or of two CSG objects themselves or any combination thereof. The CSG tree which gets formed as a result of the above
   code is also shown. Some examples of CSG union are shown below -
   

   Sphere & Cylinder	Sphere & Cone	Cylinder & (Sphere & Cylinder)

   
   
2. Intersection -
   An intersection CSG object C (where C = A intersection B) will contain all the points which belong to A AND B. Intersection is specified exactly
   in the same manner as an union and the tree formed is also similar. Some examples of CSG intersection are shown below -
   

   Sphere & Cylinder

   
   
3. Difference -
   A Difference CSG object C (where C = A difference B) will contain all the points which belong to A AND (NOT B). Difference is specified exactly
   in the same manner as an union and the tree formed is also similar. Some examples of CSG difference are shown below -
   

   Sphere & Cylinder

   
   

Page last updated on 04 October, 2005.	AT cse.iitd.ac.in	© Parag Chaudhuri , 2009