Сетка
Введение
In FreeCAD the word "Mesh" is normally used to refer to a Mesh MeshObject (Mesh::MeshObject class), a type of object that defines 3D data but is not a solid "Shape".
Meshes are very simple objects, containing only vertices (points), edges and triangular faces. In general, they are easy to create, modify, subdivide, and stretch, and can be passed from one application to another without any loss of detail. In addition, since meshes contain very simple data, 3D applications like animation software and video games can manage very large quantities of them (millions of triangles) without using a lot of computing resources.
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.
Left: parametric shape defined by properties. Right: mesh, defined by vertices and triangular surfaces.
Usage
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 primarily designed to be a solid modeller, it is better suited to deal with solid Shapes. It can import and display Meshes in the 3D View, and the Mesh Workbench offers some commands to directly manipulate them. But in many cases the Mesh first needs to be converted to a Shape (see Part ShapeFromMesh), or the geometry needs to be recreated using solid modelling techniques from the Part Workbench or the PartDesign Workbench.
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.
More information
- Miscellaneous: Import Mesh, Export Mesh, Mesh From Shape, Regular solid, Unwrap Mesh, Unwrap Face
- Modifying: Harmonize Normals, Flip Normals, Fill Holes, Close Holes, Add Triangle, Remove Components, Remove Components Manually, Smooth, Refinement, Decimate, Scale
- Boolean: Union, Intersection, Difference
- Cutting: Cut, Trim, Trim With Plane, Section From Plane, Cross-Sections
- Components and segmentation: Merge, Split by Components, Segmentation, Segmentation From Best-Fit Surfaces
- Analyze: Evaluate and Repair, Face Info, Curvature Plot, Curvature Info, Evaluate Solid, Bounding Box Info
- Additional: Import Export Preferences, OpenSCAD Workbench, Mesh Scripting
- Materials: Solid Material, Fluid Material, Non-Linear Mechanical Material, Reinforced Material (Concrete); Material Editor
- Element Geometry: Beam Cross Section, Beam Rotation, Shell Plate Thickness, Fluid Section for 1D Flow
- Electromagnetic Boundary Conditions: Electrostatic Potential Boundary Condition, Current Density Boundary Condition, Magnetization Boundary Condition, Electric Charge Density
- Fluid Boundary Conditions: Initial Flow Velocity Condition, Initial Pressure Condition, Flow Velocity Boundary Condition
- Geometrical Analysis Features: Plane Multi-Point Constraint, Section Print Feature, Local Coordinate System
- Mechanical Boundary Conditions and Loads: Fixed Boundary Condition, Rigid Body Constraint, Displacement Boundary Condition, Contact Constraint, Tie Constraint, Spring Boundary Condition, Force Load, Pressure Load, Centrifugal Load, Gravity Load
- Thermal Boundary Conditions and Loads: Initial Temperature, Heat Flux Load, Temperature Boundary Condition, Body Heat Source
- Overwrite Constants: Constant Vacuum Permittivity
- Mesh: Mesh From Shape by Netgen, Mesh From Shape by Gmsh, Mesh Boundary Layer, Mesh Refinement, Mesh Group, Erase Elements, FEM Mesh to Mesh
- Solve: Solver CalculiX, Solver Elmer, Solver Mystran, Solver Z88; Mechanical Equations: Elasticity Equation, Deformation Equation; Electromagnetic Equations: Electrostatic Equation, Electricforce Equation, Magnetodynamic Equation, Magnetodynamic 2D Equation, Static Current Equation; Flow Equation, Flux Equation, Heat Equation, Solver Job Control, Run Solver
- Results: Purge Results, Show Result, Apply Changes to Pipeline, Post Pipeline From Result, Pipeline Branch, Warp Filter, Scalar Clip Filter, Function Cut Filter, Region Clip Filter, Contours Filter, Glyph Filter, Line Clip Filter, Stress Linearization Plot, Data at Point Clip Filter, Calculator Filter; Filter Functions: Plane, Sphere, Cylinder, Box; Data Visualizations: Create Lineplot, Create Histogram, Create Table
- Utilities: Clipping Plane on Face, Remove All Clipping Planes, FEM Examples; Clear FEM Mesh, Display Mesh Info
- Additional: Preferences; FEM Install, FEM Mesh, FEM Solver, FEM CalculiX, FEM Concrete; FEM Element Types
- Ядро: App DocumentObject
- Базовые: App FeaturePython, App GeoFeature, Part Feature, Mesh Feature, Fem FemMeshObject
- Внутренние формы: Part TopoShape, Mesh MeshObject, Fem FemMesh
- Структура: App DocumentObjectGroup (Std Group), App Part (Std Part), App Link
- Производное: Part Part2DObject, Sketcher SketchObject, PartDesign Body, PartDesign Feature
- Начинающим
- Установка: Загрузка, Windows, Linux, Mac, Дополнительных компонентов, Docker, AppImage, Ubuntu Snap
- Базовая: О FreeCAD, Интерфейс, Навигация мыши, Методы выделения, Имя объекта, Настройки, Верстаки, Структура документа, Свойства, Помоги FreeCAD, Пожертвования
- Помощь: Учебники, Видео учебники
- Верстаки: Std Base, Arch, Assembly, CAM, Draft, FEM, Inspection, Mesh, OpenSCAD, Part, PartDesign, Points, Reverse Engineering, Robot, Sketcher, Spreadsheet, Surface, TechDraw, Test Framework