An Interactive Constraint-Based Graphics System with Partially Constrained Form-Features

The paper considers a 2D constraint-based geometric modelling system which distinguishes between an auxiliary and a visual geometry. The former consists of points, lines, and circles, and the later includes line segments, arcs, circles and cubic Bézier curve segments. Geometric constraints are applied only upon the auxiliary geometry. Some constraints and the majority of auxiliary geometry are extracted by the system automatically what liberates the user from giving self-understandable facts. This separation of the geometry enables developing a simple but efficient approach to constrain the cubic Bézier curves. The system can work with under-constrained parts of geometric objects what makes it interactive entirely. The paper includes a practical example of the design in the constraint-based environment and gives an insight into a user interface used.