Mesh

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Introduction

Dans FreeCAD, le mot "Mesh" est normalement utilisé pour désigner un Mesh Object (Mesh::MeshObject class), un type d'objet qui définit les données 3D mais n'est pas un solide "Shape".

Les maillages sont des objets très simples, ne contenant que des sommets (points), des arêtes et des faces triangulaires. En général, ils sont faciles à créer, à modifier, à subdiviser et à étirer, et peuvent être transmis d'une application à une autre sans aucune perte de détails. De plus, comme les maillages contiennent des données très simples, les applications 3D comme les logiciels d'animation et les jeux vidéo peuvent en gérer de très grandes quantités sans utiliser beaucoup de ressources informatiques.

However, in the field of engineering meshes present one big limitation: they are only made of surfaces, and have no "mass" information, so they don't behave like "solids". This means that solid-based operations, like boolean addition or subtraction, are difficult to perform on meshes. Also, since they are defined by individual points, they are hard to describe in a parametric fashion.

See Mesh MeshObject for more information about this type of object, and see Polygon mesh for generic information in computer systems.

How to use

Meshes are normally created by internal functions of the Mesh Workbench, or by importing mesh format files, like STL and OBJ.

Essentially, every object derived from a Mesh Feature (Mesh::Feature class) is expected to hold and manipulate a Mesh.

Since FreeCAD is designed to be a solid modeller primarily, it is better suited to deal with solid Shapes. It can import and display Meshes in the 3D view, but to transform them or create new geometry, the Mesh first needs to be converted to a Shape (see Part ShapeFromMesh). In many cases, this conversion is not automatic, and requires re-creating the geometry using solid modelling techniques, making use of Part and PartDesign tools.

Finite element meshes

In FreeCAD the word "Mesh" may also refer to a specific object that will be used in finite element analysis (FEA).

When an object with a solid Shape is used in the FEM Workbench it will be discretized into a triangular mesh. In this case, the resulting object is a Fem FemMeshObject (Fem::FemMeshObject class), and is not derived from a Mesh Feature (Mesh::Feature class).

For more information see FEM Workbench and FEM Mesh.