1.1 Geometry: geometrical entity definition

Gmsh uses a boundary representation (“b-rep”) to describe geometries. Models are created in a bottom-up flow by successively defining points, oriented lines (line segments, circles, ellipses, splines, …), oriented surfaces (plane surfaces, ruled surfaces, triangulated surfaces, …) and volumes. Compound groups of geometrical entities (called “physical groups”) can also be defined, based on these elementary geometric entities. Gmsh's scripting language allows all geometrical entities to be fully parameterized.