## An Improved Ray Shooting Method for Constructive Solid Geometry Models via Tree Contraction (1990)

Citations: | 3 - 2 self |

### BibTeX

@MISC{Goodrich90animproved,

author = {Michael T. Goodrich},

title = {An Improved Ray Shooting Method for Constructive Solid Geometry Models via Tree Contraction},

year = {1990}

}

### OpenURL

### Abstract

In the Constructive Solid Geometry (CSG) representation a geometric object is described as the hierarchical combination of a number of primitive shapes using the operations union, intersection, subtraction, and exclusive-union. This hierarchical description defines an expression tree, T , called the CSG tree, with leaves associated with primitive shapes, internal nodes associated with operations, and whose "value" is the geometric object. Evaluation of CSG trees is an important computation that arises in many rendering and analysis problems for geometric models, with ray shooting (also known as "ray casting") being one of the most important. Given any CSG tree T , which may be unbalanced, we show how to convert T into a functionally-equivalent tree, D, that is balanced. We demonstrate the utility of this conversion by showing how it can be used to improve the worst-case running time for ray shooting against a CSG model from O(n 2 ) to O(n log n), which is optimal. Keywords: Boolean a...