Initial Approximation

Creating a parametric drawing involves incremental changes, adding or deleting objects and constraints, as well as varying dimensions. Each new request for calculation of constraints system is based on the initial state of geometric objects remaining as a result of the previous GCE_Evaluate request.

It should be kept in mind that an initial geometry state is an indispensable preliminary condition required to satisfy the constraints. Two sketches that have the same set of geometric objects and constraints, but various initial states, can have various solutions. C3D Solver takes into account the initial state and it tries to satisfy all the given constraints with minimum deviations from the initial approximation and to change the minimum number of objects.

The initial approximation plays the key role not only when the calculation is requested, but also when the constraints are created. Mutual arrangement of geometric objects shows a constraint definition variant. For example, if one circle is located inside another one, then when a tangency is added for the two circles (GCE_AddTangent), then the solver would create such tangency when one circle would always remain inside the other one. Mutual arrangement of geometric objects is described in more detail in Item Mutual Object Positioning.