At a glance

As an example, consider how LGS is used in Lege'n'd system (you can download it via our download section). Lege'n'd application allows users to easily produce complicated models with hundreds of objects and constraints of different types.

You can apply many standard and advanced CAD-features like

• save/restore model;
• zooming and panning;
• using rectangular or circular coordinate grid;
• using object and constraint tree;
• using "quick constraint" feature;
• incremental solving;
• moving objects and changing constraint parameters;
• performing of degrees of freedom analysis;
• detection of overdefined parts;
• associate a variable with a constraint parameter/help parameter and introduce equations;
• apply automated constraining function to an unconstrained or partially constrained sketch;
• optimize goal parameter under geometric and engineering constraints;
• immediate interrupting of calculations.

In the current version Lege'n'd supports the following types of objects:

• points;
• lines and segments;
• circles with fixed and non-fixed radius;
• ellipses with fixed and non-fixed radii;
• circular and elliptic arcs;
• splines;
• parabolic and hyperbolic segments;
• polylines;
• variables.

and these types of constraints:

• fixation;
• coincidence;
• concentricity;
• distance;
• angle, perpendicularity and parallelism;
• tangency;
• midpoint;
• symmetry;
• equal distance and equal radii;
• fixation of ellipse radii and fixation of circle radius;
• angle with Ox coordinate axis;
• verticality;
• horizontality;
• vertical and horizontal distance;
• polyline length;
• equations and inequalities for variables.

Constraint approach makes sketching much simpler, because the user does not need to carefully draw each line, caring about angles and distances, to get the precise design. Instead, the user can sketch out a draft design and impose all necessary constraints. The design will be automatically modified to satisfy the constraints, resulting in the final, precise form (see example below).

LGS provides a lot of power to make constraint-based sketching truly interactive. Models with about a hundred of geometries and constraints are calculated in a fraction of a second. One can create the sketch below without visible delay and then interactively modify any constraint.

The system below can even be animated (by changing constant parameters or moving some part) to show the kinematics of the sketch.