Evaluating the intersection of two rational parametric surfaces is a recurring operation in solid modeling. However, surface intersection is not an easy problem and continues to be an active topic of research. The main reason lies in the fact that any good surface intersection technique has to balance three con icting goals of accuracy, robustness and e ciency. In this paper, we formulate the problems of curve and surface intersections using algebraic sets in a higher dimensional space. Using

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... sults from Elimination theory, w e project the algebraic set to a lower dimensional space. The projected set can be expressed as a matrix determinant. The matrix itself, rather than its symbolic determinant, is used as the representation for the algebraic set in the lower dimensional space. This is a much more compact and e cient representation. Given such a representation, w e perform matrix operations for evaluation and use results from linear algebra for geometric operations on the intersection curve. Most of the operations involve e v aluating numeric determinants and computing the rank, kernel and eigenvalues of matrices. The accuracy of such operations can be improved by pivoting or other numerical techniques. We use this representation for inversion operation, computing the intersection of curves and surfaces and tracing the intersection curve o f t w o surfaces in lower dimension.