Changes

===Working with STL Models=== Stereolithography files contain a tessellated (triangulated) representation of a structure. [[EM.Cube]] treats STL files in a special way. You can export the project structure into a STL file in the form of a polymesh object. This is similar to writing the structure mesh data into a mesh data file of ".msh" extension. The project structure is tessellated using CubeCAD's triangular surface mesher of the '''Structured Type'''. [[EM.Cube]] gives you two options for STL export: '''Binary STL''' and '''ASCII STL'''. The latter file is bigger in size. You can import STL files of both binary and STL types into [[EM.Cube]]. STL models are imported as native polymesh objects. As a result, you can edit the imported objects and modify their various parameters arbitrarily. This is in contrast to importing files of other formats, which create solid and surface objects of the generic type. Once you import a STL file, you can change the mesh type of the imported object to the '''Regular Type'''. You can also decrease the '''Edge Length''' to obtain a higher resolution. Just like other polymesh objects, you can insert nodes on the faces and edges or delete nodes from the imported object. === CubeCAD's Triangular Surface Mesh ===

Mesh generation is an important part of computational engineering. A mesh is used to discretize a continuous geometry into a set of much simpler elementary cells or "mesh "elements". Solid objects can be discretized into tetrahedral elements. Surfaces can be meshed using triangular cells. Curves can be discretized into polylines". As you will see in [[EM.Cube]]'s other modules, [[EM.Cube]] provides a large number of diverse several mesh generatorsof different types. The accuracy of a numerical simulation often depends directly on the quality of the mesh. It is also important to be control the and resolution of a mesh, namely, the size of mesh cells. Higher mesh resolutions normally lead to better accuracy of the numerical results.

Tetrahedral and surface triangular meshes are one of the most widely used mesh types in many different engineering disciplines. CubeCAD provides two types of mesh generation algorithms for [[Discretizing Objects|discretizing objects]]. The first one generates a wire-frame triangular surface triangular mesh of generator that discretizes surface objects and a polyline mesh the surface of curve objects. The solid objects are treated as closed surfaces and are discretized using based on a similar wire-frame surface mesh. in other words, objects of all types are meshed in some sort. The wire-frame mesh generator has two variationsspecified edge length. The first mesher algorithm generates a regularized mesh and attempts to create triangular cells of almost equal size. The second algorithm tries to create a structured mesh with cells of similar patternsarea. CubeCAD's other mesh generator generates a tetrahedral mesh for solid objects. Tetrahedral meshes are usually enormous in size. Note that surface and polygonizes curve objects cannot be discretized using this type of mesh generatorbased on the same edge length.

===Generating and Controlling the Mesh===

You can generate a mesh of # By clicking the structure in CubeCAD in one '''Show Mesh'''[[File:mesh_tool_tn.png]] button of the following three ways:Simulate Toolbar.# By selecting the menu item '''Simulate → Discretization → Show Mesh'''.# Using the keyboard shortcut {{key|Ctrl+M}}.

# By clicking the '''Show Mesh'''[[File:mesh_tool_tn.png]] button of '''Compute Toolbar'''.# By selecting '''Menu [[File:larrow_tn.png]] Compute [[File:larrow_tn.png]] Discretization [[File:larrow_tn.png]] Show Mesh'''.# Using the keyboard shortcut '''Ctrl+M'''. When the mesh is displayed in the Project Workspaceproject workspace, [[EM.Cube]]'s mesh view mode is enabled. In this mode, all the objects are discretized using the selected CubeCAD's mesh generation algorithm and the meshes of all objects are displayed. In mesh view, you cannot mouse-over, select or edit any objects. The mesh view is for viewing purpose only. You can perform most of view operations such as zooming in and out using the mouse scroll wheel, rotating the view using the right mouse button '''{{key|RMB''' }} and panning the view using '''{{key|Shift+RMB'''}}. When [[EM.Cube]] is in mesh view mode, the '''Show Mesh'''[[File:mesh_tool_tn.png]] button of Simulate Toolbar remains depressed. To hide the mesh, exit the mesh view mode and return to the normal view mode, simply click the '''Show Mesh'''[[File:mesh_tool_tn.png]] button one more time to toggle its state, or press the keyboard's '''{{key|Esc Key''' }} (Escape)key, or select the menu item '''Simulate → Discretization → Show Mesh''' and remove the check mark in front of it.

You can change the mesh type and the mesh resolution from the CAD BubeCAD's Mesh Settings Dialogdialog. Click the '''Mesh Settings'''[[File:mesh_settings_tn.png]] button of '''the Simulate Toolbar''' or select the menu item '''Simulate → Discretization → Mesh Settings...'''In the drop-down list labeled '''Mesh Type''' you can select one of the three two options: '''Regular Surface''', or '''Structured Tessellated Surface''' or '''Tetrahedral'''. The latter option shows the simplest tessellation of the physical structure. The mesh resolution is controlled by '''Edge Length''' , which is expressed in project units. The default value of edge length is 10 units. This means that the default mesh features cells with a size of about 10 units. When you change the mesh type or resolution, you can see the effect using the '''{{key|Apply''' }} button if [[EM.Cube]] is already in mesh view mode. After [[EM.Cube]] generates a mesh, it saves its and uses it the next time you want to see the mesh. The mesh stays the same until you change its parameters. Sometimes, you may want to regenerate the mesh with the same current parameters. To do so, select the menu item '''Simulate → Discretization → Regenerate Mesh'''. ===Working with STL Models=== Stereolithography files contain a tessellated (triangulated) representation of a structure. [[EM.Cube]] treats STL files in a special way. You can export the project structure into a STL file in the form of a polymesh object. This is similar to writing the structure mesh data into a mesh data file of ".msh" extension. The project structure is tessellated using CubeCAD's triangular surface mesher of the '''Structured Type'''. [[EM.Cube]] gives you two options for STL export: '''Binary STL''' and '''ASCII STL'''. The latter file is bigger in size. You can import STL files of both binary and STL types into [[EM.Cube]]. STL models are imported as native polymesh objects. As a result, you can edit the imported objects and modify their various parameters arbitrarily. This is in contrast to importing files of other formats, which create solid and surface objects of the generic type. Once you import a STL file, you can change the mesh type of the imported object to the '''Regular Type'''. You can also decrease the '''Edge Length''' to obtain a higher resolution. Just like other polymesh objects, you can insert nodes on the faces and edges or delete nodes from the imported object.