About LGS 2D                  About LGS 3D

LGS 2D is a computational module engineered to support two-dimensional parametric sketching/drawing in CAD and computer graphics systems, as well as any other application that requires parametric connections or constraints to be set between geometrical objects.

LGS 2D supports creation and modification of the geometric models by means of (explicit or implicit) constraints. Typical geometric objects are points, lines, circles, or black-box parametric curves. Objects can be fixed in the absolute coordinate system or with respect to each other (the latter feature is provided by the so-called rigid sets of objects). A set of geometric constraints includes logical constraints between geometric entities (like coincidence, parallelism, tangency, etc.), and dimensional constraints (that specify the required values for the given distances, angles or radii). LGS 2D also supports user-defined variables, algebraic and black-box equations, and tabular constraints that can be arbitrarily mixed with geometric dimensions. LGS 2D moves and rotates objects to positions where all constraints are satisfied with minimal possible transformations of the initial configuration. LGS 2D is a simultaneous solver: it can solve cyclic dependencies between constraints. Both under-constrained and over-constrained models can be efficiently solved. Additional features of LGS 2D are dynamic constraint solving (while dragging an object) and redundant/inconsistent constraint diagnostics.

LGS 2D is a cross-platform software package. It is a set of binary libraries that runs under all 32- and 64-bit Windows, Linux, *BSD, AIX, HP-Unix, Sun Solaris, MacOS and other OS. Coded in C++, LGS 2D has an API declared in pure C to be integrated into a broad range of software applications. LGS 2D can be used as a self-supporting component, or jointly with LGS 3D version. Both 2D and 3D versions have similar API, providing a complete parametric solution for all aspects of CAD/CAM/CAE system functionality - from 2D sketching to history-free parametric 3D modeling, assembly design, kinematic simulation, etc.

A sample sketching application called Lege'n'd 2D is available as a free download at the LEDAS web site with a set of representative examples of different industrial sketches. This application can be used by anyone to test functionality, robustness and performance of LGS 2D. It was created with the Open CASCADE open-source application framework. The source code of Lege'n'd 2D is available under special request.

Current version is LGS 2D 4.0

Version 4.0 of LGS 2D introduces the following new functions: linear pattern constraints, directed distance constraints, and alignment and orientation attributes for most constraints.

Linear pattern constraints set relations between several sub-geometries of equal shapes (e.g. rectangles), aligning and uniformly distributing them along a given direction. Any changes in position or orientation of any one of the pattern constraint’s arguments leads to corresponding changes in other arguments. As with other LGS 2D constraints, a linear pattern constraint is variational, which means it can be combined with other constraints that are imposed on pattern’s sub-geometries. All constraints are solved simultaneously.

Directed distance is a new constraint that generalizes horizontal and vertical distance constraints introduced in previous versions of LGS 2D. It is a ternary (three-element) constraint imposed on any pair of objects (points, circles, or curves) and a line that represents the direction of distance measurement. It can be used to prevent segments from flipping their end points; using a signed, directed distance constraint (instead of the ordinary distance) fixes the desired relative locations of the end points.

Alignment attributes specify whether the tangent vectors of the constraint arguments are co-directed (collinear vectors with positive scalar product) or counter-directed (collinear vectors with negative scalar product). The attribute can be applied to any constraint involving two non-point entities: tangency, distance, parallelism, or perpendicularity between lines, circles, curves or ellipses.

Orientation attributes control whether an argument is positioned to the left or right side of other ones. They are applied to all distance constraints, except point-point distances. Orientation and alignment attributes fully control the chirality (left or right handedness) of constraints.

For the full list of changes see Release Status page.