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Import CAD files

XR Twin can process and import a wide range of 3D files covering most of the major industrial CAD files standards (see supported formats at the end of this section). To import a 3D file, click on Object/Import from the menu or on the Import button from the side bar and select the CAD file.

Import

Import parameters

Import

The settings used to import a 3D model will impact the performance of your simulation. There is no set of preferences that will work every time, as every use-case is different.

  • Mesh Quality (only for B-Rep type objects): defines the quality (triangle density) of the imported model. A higher quality means more triangles computed from the original object, hence more precision and quality in the simulation but less performance.
  • Scale factor : XR Twin default unit is meters. Modify scale factor if the imported file was designed with a CAD software with different unit system.

  • Merge final levels : Sometimes, objects created from CAD software are delivered as multiple sub-surfaces disconnected from one another, while they should be unified as a single object. Use this setting to assemble together unconnected CAD surfaces of hierarchy nodes into one single object.

  • Prefer existing mesh : some CAD files may already contain a polygonal representation (usually low quality) for visualization purposes. If the 3D loader fails to compute triangle sets for the given part, use this setting to import the embedded polygonal representation.

B-Rep Vs Meshes

There are two primary file types you can use for importing 3D objects: BRep and mesh files. It is important to understand the difference between these file types and in general, use BRep type files when possible (native file formats).

Import

BRep (Boundary Representation) files describe 3D objects using precise geometric and topological information. BRep files define the shape, dimensions using mathematical equations (e.g. a cylinder is represented by a length and a radius). BRep files are commonly used in CAD (Computer-Aided Design) applications (CATIA, Solidworks, Siemens).

When importing BRep files into XRTwin, the software will interpret and convert the BRep data into a set of polygons, suitable format for rendering and interaction within the virtual reality environment.

Mesh files, on the other hand, represent 3D objects using a collection of interconnected polygons. This polygonal representation is also often referred to as faceted, tessellated or triangulated. Meshes provide a simplified representation of the object's geometry by approximating its surfaces. The number of triangles in the polygonal representation depends on accuracy used when approximating the original precise B-Rep representation.

The images below demonstrate the same object in B-Rep or mesh format.

Recommendation For relevant workflow, the imported model should come from a Brep file type (native CAD format). This allows you to properly set the resolution of the triangulated model on import and ensures that no valuable information (structural, hierarchy) is lost.

Model analysis and shape detection

After importing a model in the scene, a background process will analyze the parts and compute possible shapes from the topology that can be used later on for defining mechanical constraints, measure points and so on. These process might take some time and status is indicated by the progress bar at the bottom of the hierarchy panel. The part features are then stored in the project so XR Twin does not have to recalculate part shapes when reopening a project.

Degraded performance during model analysis

Analyzing a complex assembly can be performance consuming. Degraded XR Twin performance may occur during this process so it is advised to wait for the end of the analysis before launching the simulation.

Move part origin

You can edit the origin of your part local frame. This is useful for scenario authoring when part origin is far from the 3D model and you have trouble to align the object to its target.

To move the origin of the part:

  • Right click on the desired node in the working tree
  • Click on Move Origin
  • Select a new origin in the 3D view

Working with large assemblies

When working with large 3D models in XRTwin, it is important to optimize your scene for optimal performance. Here are some best practices to follow:

  1. Assess Graphics Frame Rate

    After importing a model, open the statistics panel Import in XRTwin to assess the graphics frame rate. This metric indicates how many images are rendered per second. If the frequency is too low, it may be due to the presence of too many objects in the scene, which can impact performance.

    Import

  2. Merge Static Objects

    Consider merging together objects that serve only for decoration and won't be interacted with. This practice helps reduce the overall complexity of the scene. To merge objects, right-click on a parent node in the hierarchy and select "Merge". This process combines all child nodes into a single Group entity, reducing the number of draw calls and improving performance. This action can be reversed: right-click on the Group node and select "Unmerge".

  3. Adjust the Level of Detail (LOD)

    In 3D graphics, Level of detail or LOD is an optimization technique that hides small objects that are far away from the point of view. XRTwin allows you to adjust the Level of detail setting in the project preferences (Menu Project>Preferences>Graphics). By optimizing the LOD, you can reduce the number of rendered objects, improving performance without sacrificing visual quality.

    Import

  4. Disable Shadows

    While shadows can enhance realism and create a sense of depth in your scene, they can also be computationally expensive. If you're experiencing performance issues with large 3D models, consider disabling shadow rendering. This setting can be adjusted in the preference panel of XRTwin.

By following these optimization techniques, you can ensure that your large 3D models run smoothly in XRTwin, providing an immersive and efficient virtual reality simulation experience.

Supported CAD files formats

Format
Extension
Version
3D PDF .pdf All
3D XML .3dxml Version 4.0 - 4.3
3DS .3ds All
3MF .3mf All
ACIS .sat, .sab R2.0 and newer
CATIA .CATPart, .CATProduct V5 and V6
COLLADA .dae All
AutoCAD 3D .dwg, .dxf All
Autodesk FBX .fbx 2012 and newer
glTF .gltf, .glb 2.0
IFC .ifc IFC 2x Editions 3 and 4
IGES .igs, .igesC All
Inventor .ipt, .iam 2015 to 2021
JT .jt v8.x to v10.x
OBJ .obj All
Open Cascade .brep All
Parasollid .x_t, .x_b All
PLY .ply All
PRC .prc All
PTC Creo .prt, .asm All
Rhino 3D .3dm Up to 7
SIEMENS NX .prt All
Solid Edge .asm, .par, .psm All
Solidworks .sldprt, .sldasm 2004 to 2021
STEP .stp, .step AP203, 214, 242
STL .stl All
U3D .u3d All
USD .usd, .usda, .usdc, .usdz All
VRML .wrl V1/1995 and v2/1997
X3D .x3d All