Overview of CAD data formats

Overview of common CAD data formats and description

In the diverse application areas of 3D laser scanning, different requirements are often made on the CAD exchange formats. This list is intended to serve as a quick guide for the practitioner and shows the common formats in detail.

.stl

• Description of the surface of 3D solids with the help of triangle facets.
• Triangle facet is characterized by the 3 vertices and the corresponding surface normal of the triangle
• Data volume can reach enormous sizes
• Curved surfaces are only approximated by the triangles

.vrml

• Features triangulated surfaces
• Avoids redundancies
• There are 2 numbered lists:
  The 1st list includes the coordinates of the triangle vertices,
  in the 2nd list, the triangles are defined by the position number of the point list.
• Geometry element is required to distinguish inside from outside
• Time required to build a virtual model is not very different for both formats, but is different in memory requirements and data transfer
• Can add colors or textures to surfaces
• .vrml has a clear advantage over .stl
• Is not correctly generated or read by all systems

.stp, .step

• STEP files; (Standard for the Exchange of Product model data)
• This is an interface standard initiated by ISO, which goes beyond the pure exchange of geometry data (as via DXF or IGES).
• As much product data as possible, which is generated during the product life cycle, can be represented and transferred between different CAx systems.
• All shapes (wire, surface, solid) of CAD data models can be integrated in the geometry description
• With STEP, it is possible to pass on information about the hierarchical structure for assemblies

.vda

• Primarily for the exchange of automotive body data and castings
• Especially suitable for the exchange of free-form surfaces created with surface-oriented 3D software
• Points, point groups and vectors can be transferred
• Exchange of solid models is not possible
• Geometry data should be described

.igs, .iges

• ANSI-compatible, non-proprietary public domain file format.
• Used for the exchange of product definition data between different CAD/CAM systems
• Primarily developed for the transfer of geometry data
• With version 5.3, IGES also features solid elements

.dxf

• ASCII or binary file format for the exchange of vector data between CAD programs.
• Developed by Autodesk, it plays a role mainly as an interface from and to AutoCAD

.x_t Parasolid Datei

• 3D CAD kernel format from e.g. Unigraphics, Solidworks, ANSYS.
• It is a 3D CAD solid modeling kernel from the company Unigraphics Solution
• Provides a library of C++ functions

.sat

• ACIS file
• ACIS is written in the object-oriented programming language C++ and features an open system architecture
• Wire and surface models can be managed and manipulated
• Imported models with inaccurate geometry descriptions can be processed correctly

.ply  

• Polygon file format
• Used in particular for the production of colored parts
• Saves the color value, too
• Similar to VRML

.dwg

• DWG format is a proprietary binary file format for 2D and 3D design data and metadata.
• Native format of some CAD programs like AutoCAD, DraftSight, BricsCad and many others

.rvt    

• The RVT file (.rvt) is Autodesk's proprietary format for Revit files.
• Revit files contain geometric data as well as the factual data of components
• RVT format is used by Autodesk Revit software
• Not an open file format
• Defined by Autodesk

.ifc      

• Represents Industry Foundation Classes
• Is a worldwide exchange format in the construction industry and is also used for data exchange for BIM programs
• Open format
• Is defined by the association buildingSMART
• In terms of structure, it is an ASCII text file

.fbx 

• Autodesk Blender Proprietary File Format

.skp

• Trimble Sketchup file format
• Formerly a development of Google Sketchup
• Contains 2D/3D geometry information

.3dm

• Format of the software Rhino from the manufacturer MCNeel.
• Very popular 3D software; besides its strength in freeform surfaces, the software has many interfaces
• Open file format

.3ds 

• Native format from Autodesk 3D Studio
• Binary file format

.prt

• File format of the PTC Creo Parametric software.
• Contains design data as model data and the part structure (parametric)

.ipt

• Autodesk Inventor proprietary format
• IPT stores parts
• Optional IAM format available which stores assemblies
• Can be used in Autodesk Inventor and in 3D Studio Max