A Direct Modeling Method for 3D CAD Models Preserving Columnar Features

Aiming at the problem that traditional 3D CAD model editing often changes the topology information of models and relies on modeling feature information, this paper proposes a direct modeling method for CAD models that preserves columnar body features. This method builds columnar body features based on boundary representation(B-Rep), propagates editing operations within the columnar body features, modifies associated geometric elements while maintaining the topology. The method mainly includes defining a columnar body feature based on B-Rep, which maps direct modeling operations for points, edges, and faces to editing the surface elements of the feature; providing a constraint propagation algorithm for columnar body features, which determines the effectiveness of editing operations through constraint solving and meets user intent. Based on the open source CAD engine Open CASCADE(OCC), an experimental verification is conducted on hexagonal frustums, circuit board models, etc., which proves the effectiveness of the method.