Geometric modeling
The synthesis of solids bounded by many faces
Communications of the ACM
An algorithm and data structure for 3D object synthesis using surface patch intersections
SIGGRAPH '82 Proceedings of the 9th annual conference on Computer graphics and interactive techniques
Polygon comparison using a graph representation
SIGGRAPH '80 Proceedings of the 7th annual conference on Computer graphics and interactive techniques
Accurate Solid Modeling Using Polyhedral Approximations
IEEE Computer Graphics and Applications
Incremental Boundary Evaluation Using Inference of Edge Classifications
IEEE Computer Graphics and Applications - Special issue on computer-aided geometric design
Architectural Issues in Solid Modelers
IEEE Computer Graphics and Applications
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To integrate a CSG-based solid modeler into an existing wireframe/surface modeling system, new boundary evaluation technology has been developed. This scheme uses exact representations for the simple quadric surfaces and both exact and approximate representations of higher-order curved surfaces. It supports parametric primitives (box, wedge, sphere, cylinder, cone, torus), procedural primitives (extrusion, revolution, tube) and a sculptured surface primitive. The output includes curves, parametric trimmed surfaces, and a data structure of adjacency information.An existing boundary evaluator (PADL-2's) has been enhanced to allow a general non-convex faceted primitive with planar and quadric facets. This new hybrid evaluator combines two techniques for curve/primitive classification. PADL-2's existing halfspace-based classification is reserved for the simple convex primitives, and a new ray firing based classification is applied to the non-convex primitives. After evaluation, approximate intersection curves (from intersections involving higher order surfaces) are refined to a specified tolerance by exploiting an exact parametric representation of the surfaces of the primitives. The refined curves and the quadric surface intersection curves are used to create a parametric trimmed surface representation of the solid. This combination of techniques and representations offers advantages in accuracy, robustness and efficiency suitable to a production environment.