3D file formats are used to store information about 3D models. You've probably heard of some of the most popular formats, including STL, OBJ, FBX, and DAE. They are used in a wide variety of applications ranging from video game animation to industrial additive manufacturing.
In this article, we'll consider why there are so many different formats, explore four key features of 3D file format storage, discuss how to choose which file format to use, and then we'll drill down into the 10 most common in use today 3D file formats to help you choose the right 3D file format for your project! Last but not least, you can use the online tool 3DConvert to convert between different 3D file formats!
1. What is a 3D file?
The basic function of a 3D file is to store information about a 3D model in a format that a computer can understand (either plain text or binary data).
Specifically, they store detailed information about four key functions of a 3D model, though it's worth noting that you may not always take advantage of all four in all projects, and not all file formats support all four. function!
The four key characteristics that a 3D file can store include the model's geometry, the model's surface textures, scene details, and the model's animation.
Before exploring these features and how to use them, let's quickly review the types of 3D files.
2. Types of 3D files
There are literally hundreds of different 3D file formats, each with its own reason for being and being used! However, most file types can be divided into two categories: private and neutral.
- private format
Proprietary format file types such as DWG files for AutoCAD or BLEND files for Blender. They are specifically created to be used with specific software, which gives them some distinct advantages as they are optimized for use with the software. This tends to make the design process much faster and smoother.
The disadvantages may be less obvious, but they are also worth considering. Since the file type is proprietary, it is unlikely to work with other software. For example, if you're using Blender and the person you want to collaborate with is using AutoCAD, they won't be able to open and use any BLEND files you send them!
This is where the second file format comes in.
- neutral format
The neutral file format works cross-platform, which means you can create a file in one program, send it to someone using a different software, and they will be able to use the same file! Neutral formats also provide a great way to leverage proprietary formats and solve cross-platform compatibility issues. Neutral file formats include STL, OBJ, 3MF, and more.
If we take the same example above, when you have a BLEND file that you want to send to collaborators to work on in AutoCAD, you can take advantage of the optimized BLEND format when working on that file, and then export the model as a neutral file type, e.g. OBJ, since most CAD software (including Blender) supports OBJ.
Your collaborators can then take that neutral file type and open it in AutoCAD without any issues. Later, they can even save it as DWG, further taking advantage of the format's optimizations!
3. Main functions of 3D files
We briefly mentioned earlier that a 3D file can store four key characteristics: the geometry of the model, the surface textures of the model, the details of the scene, and any animation of the model.
Let's take a deeper look at these features and consider why you might need to store this information and how this might affect the file type you choose to use!
3.1 Geometry
Every 3D model has a unique geometry, and the ability to store that geometry is an essential feature of any 3D file format.
There are three methods of encoding surface geometry, each with its advantages and disadvantages. They are Approximate Mesh, Exact Mesh, and Constructive Solid Geometry (CSG).
- Approximate Trellis Coding
In approximate mesh coding, the surface of a 3D model is covered with a mesh of tiny polygons, usually triangles. This process is also known as "tessellation," and therefore these file formats are also called tessellation formats.
The same subdivision model, from higher (left) to lower (right) polygon count
Polygons approximate the smooth geometry of the model's surface, which means you can lose accuracy in the model's geometry. In general, accuracy can be improved by using more polygons, but this also results in larger file sizes, so these formats are best for applications that don't require very high resolution models.
3D printing is a good example. 3D printers cannot print files beyond a certain resolution, so this type of file is perfect for the job. In fact, the most popular 3D printing file format, STL, is a tessellation format.
- exact mesh coding
For those cases where approximate or subdivided meshes are not precise enough, we have exact meshes.
NURBS region (green) defined by 36 control points (red)
The exact file format uses non-uniform rational basis splines (NURBS, a computer-generated mathematical model) to form surfaces instead of polygons. These parametric surfaces consist of a small number of weighted control points and a set of parameters called nodes. From the knots, the surface can be calculated mathematically by smooth interpolation over the control points.
This makes surfaces appear smooth at any scale and accurately reproduces the smallest details of 3D models. However, while accurate meshes are accurate at any resolution, they render much slower!
- Constructive Solid Geometry (CSG)
The final method of storing surface geometry is called CSG. Using this method, a design can be built block-by-block using primitive shapes that are combined using Boolean operations such as union, intersection, and difference.
Combine cubes and cylinders to create new compound shapes
CSG is very user-friendly because you can build models bit by bit with familiar shapes. It also has the advantage that each individual editing step is stored in a 3D file format so that any step can be undone and redone at any time.
3.2 Surface texture
The second most common feature stored in a 3D file format is surface appearance.
The same sphere with a different texture applied
There are some applications (3D printing being a prime example) that don't require this because you only need the geometry of the shape. However, in many applications the appearance of the 3D model is very important. For example, no one wants to play a video game with an untextured, uncolored model.
As with its geometry, information about the appearance of a model's surface can be encoded in different ways.
- texture mapping
In texture mapping, each point on the surface of a 3D model (or polygonal mesh) is mapped to a two-dimensional image.
2D image (right) mapped to 3D model (left)
The coordinates of a 2D image have attributes such as color and texture, and when rendering a 3D model, each surface point is assigned a coordinate. The vertices of the mesh are mapped first, then other points are assigned coordinates by interpolating between the vertex coordinates.
Most 3D file formats support texture mapping, but 2D images containing texture information are sometimes stored in separate files, depending on the format.
- surface properties
Another common way to store texture information is to assign a set of attributes to each face of the mesh. Common attributes include color, texture, and material type. Additionally, surfaces can have a specular component, indicating the color and intensity of true specular reflections from light sources and other nearby surfaces.
3D model with properties and components to make it look like glass
Surfaces can also be transparent or translucent, encoded by a transmission component that describes the color and intensity of light passing through the surface. Transparent surfaces often distort the light passing through them, and this distortion can be represented by a property called "Index of Refraction", which is determined by the model's material type.
3.3 Scene Details
Scene information describes the layout of the 3D model in terms of cameras, light sources, and other nearby 3D models.
Lights created in Blender
The position and details of any camera as well as details of light source position, intensity and color can be stored in the 3D file itself. Spatial relationships between 3D models and other models are also sometimes stored. This is especially important if the model consists of multiple parts that need to be laid out in a certain way to make up the scene.
It's worth noting that most 3D file formats do not support scene information. Often, this information is not needed at all and increases the file size unnecessarily. Still, for those serious applications like video game production, it's absolutely critical!
3.4 Animation
As with scene details, not all file formats allow storage of animations. However, there are several formats that do store animation data for applications that require it, such as in video game design or film production, where animation is heavily used.
The "skeleton" of bones and joints on the left is used to manipulate and animate the 3D model on the right
The most popular way to animate 3D models is called "skeletal animation". In skeletal animation, each model has an underlying "bones" consisting of virtual "bones", and the movement of bones higher in the hierarchy affects the bones lower in the hierarchy. This is similar to the human body where the movement of the shin affects the position of the toes.
Virtual bones are also connected by "joints", which limit how the bones can move. This is again similar to the human body - the elbow can only rotate around a specified axis, while the ball joint between the thigh and pelvis allows full rotation.
5. Which 3D file format is the best?
So how do you actually choose the best file format for your project? Not an easy task when there are hundreds of file formats to choose from!
We'll dive into 10 of the most popular 3D file formats later, but here are three questions we recommend considering when considering which format is right for you.
- What will this file be used for?
There's no point wasting storage space recording information you don't need, so first consider whether you really need to store scene details, animation or surface textures, or if it's just the geometry you need.
Keep it simple as it works for your project, and choose a format that suits your use case, rather than overcomplicating the process when it doesn't have to be.
- Which software will you use?
Are you familiar with a program? Maybe you're an expert in Tinkercad but not so good at Maya?
Play to your strengths and choose a file format that is compatible with the design software of your choice. 3D modeling is probably complex enough without having to use entirely new software, if not necessary.
It's also worth considering if your preferred software has a proprietary file format, as it might be worth taking advantage of any optimizations!
- What's next?
If you know your model will be used in another program or other application, you may want to save it in a cross-platform format for easy collaboration. One of the many neutral formats might be a good idea.
It's also worth considering that you yourself may want to use the file for other purposes in the future. For example, if you want to 3D print your model, it might be worth saving it in a format recognized by your preferred slicer, such as STL or 3MF.
Remember that you can always convert file formats, although there may sometimes be unintended side effects such as loss of detail. It's always best if you can choose the right format from the start.
6. The most popular 3D file formats
Time to dive into 10 of the most popular 3D file formats.
Since 3D files are used in a variety of applications, to help you choose the right file type, we'll cover a few key points about each format:
- Key Features: These are the four key features.
- Popularity and future prospects: This is important because some files are very popular in certain industries despite the format being somewhat older and less optimized, while other formats are very modern and optimized but less common. Depending on the application and industry of your project, this is worth considering.
- Most Common Industry: Whether the file is most commonly used in the 3D printing industry, animation, defense, etc.
6.1 STL
STL (from "stereolithography") is one of the most important neutral 3D file formats for 3D printing, rapid prototyping and computer-aided manufacturing.
The same model in STL format with a different number of polygons
STL is one of the oldest 3D file formats, created in 1987 by 3D Systems CTO Chuck Hull. He also invented the world's first stereolithography 3D printer. The STL file format was originally created as an easy way to transfer 3D CAD model information to this 3D printer.
The 3D file format has the extension .stl.
The main features of STL:
- STL uses triangular meshes to encode the approximate surface geometry of 3D models.
- STL only stores the geometry of the model and is therefore one of the simplest and most compact 3D file formats.
- The STL format specifies ASCII and binary representations. Binary files are more common because they are more compact.
Popularity and future prospects:
Since its invention, the STL file format has been widely adopted by the rapid prototyping, 3D printing, and computer-aided manufacturing industries. It remains the most widely used file format for 3D printing.
STL cannot encode color information, so, for this reason, with the rise of multi-material and full-color 3D printing, STL's reign in 3D printing may not last long, and formats such as OBJ, 3MF or AMF will be in 3D printing. dominate. line to replace it.
What industries use it?
3D printing, rapid prototyping and computer-aided manufacturing.
Conversion tool: 3D model to STL
6.2 OBJ
The OBJ file format is another neutral heavyweight file format in the 3D printing world. It is also widely used in 3D graphics. It was originally developed by Wavefront Technologies for their advanced visual animation package.
OBJ model (blank female game avatar created by Alizhea)
The 3D file format has the extension .obj.
Key features of OBJ files:
- The OBJ file format supports both approximate and exact encoding of surface geometry. When approximate encoding is used, it does not restrict the surface mesh to triangular faces. Users can use other polygons, such as quadrilaterals, if they wish. When using exact encoding, it uses smooth curves and surfaces like NURBS.
- The OBJ format can also encode color and texture information. This information is stored in a separate file with the extension .mtl (Material Template Library). It does not support any kind of animation.
- The format specifies both ASCII and binary encodings, but only the ASCII encoding is open source.
Popularity and future prospects:
The OBJ file format is one of the most popular 3D graphics interchange formats due to its neutrality. As the 3D printing industry moves towards full-color printing, it is also getting more and more attention from the 3D printing industry.
What industries use it?
3D graphics and 3D printing.
Conversion tool: 3D model to OBJ
6.3 FBX
FBX is a proprietary file format widely used in the film industry and video games. It was originally developed by Kaydara, but was acquired by Autodesk in 2006. Since the acquisition, Autodesk has used FBX as an interchange format for its own product portfolio, which includes AutoCAD, Fusion 360, Maya, 3ds Max, and other software packages.
Models in FBX format
The file extension for this format is .fbx.
Key features of the FBX file format:
- The FBX file format supports geometry and appearance-related attributes such as color and texture. It also supports skeletal animation and deformation.
- Both binary and ASCII files are supported.
Popularity and future prospects:
FBX is one of the most popular animation options. Additionally, it is used as an interchange format, facilitating high-fidelity interchange between 3ds Max, Maya, MotionBuilder, Mudbox, and other proprietary software.
What industries use it?
Video game and movie industry.
Conversion tool: FBX to GLTF
6.4 DAE (Collation)
Collada files are a neutral format widely used by the video game and film industries. It is managed by the Khronos Group, a not-for-profit technology consortium.
DAE files can support all the details involved in animation
The file extension for the Collada format is .dae.
Key features of Collada format files:
- The Collada format supports geometry; appearance-related attributes such as color, material, texture; and animation. Also, it's one of the rare formats that supports kinematics and physics.
- The Collada format uses the XML markup language to store data.
Popularity and future prospects:
The original intention behind the Collada format was to be the standard for 3D file formats. In fact, in 2013, it was adopted by ISO as a publicly available specification ISO/PAS 17506. Therefore, many 3D modeling programs support the Collada format.
That said, the consensus is that the Collada format has not kept pace with the times. It used to be used heavily in film production as an interchange format for Autodesk Max/Maya, but the industry is now moving more towards OBJ, FBX and Alembic.
What industries use it?
Film and video game industry.
Conversion tool: 3D model to DAE
6.5 3DS
3DS is a proprietary file format used in architecture, engineering, education, and manufacturing. It is the native version of the old Autodesk 3D Studio DOS, a popular modeling software that was replaced in 1996 by its successor, 3D Studio MAX. Developed in the 90's, it is one of the oldest 3D file formats and has become one of the de facto industry standards for storing 3D models or exchanging between two other proprietary formats.
3DS: old but good
The format extension is .3ds.
Key features of the 3DS format:
- The 3DS file format retains only the most basic information about geometry, appearance, scene and animation. It uses a triangular mesh to approximate surface geometry, limited to 65,536 total triangles.
- It stores appearance-related properties such as color, texture, material, and transmissivity, as well as scene information such as camera position. Lights can also be stored, but this format does not support directional lights.
- The 3DS format specifies binary encoding and stores information in blocks. This allows parsers to skip chunks they don't recognize, and allows extended formats.
Popularity and future prospects:
As one of the oldest file formats, 3DS has become the standard for storing 3D models and for exchanging between other 3D file formats. Almost all 3D software packages support it.
However, since this format retains only the most essential information about the 3D model, it needed to be supplemented by the MAX format (now superseded by the PRJ format), which contains extra information specific to Autodesk 3ds Max to allow scenes to be fully saved and load.
What industries use it?
Architecture, engineering, education and manufacturing.
6.6 IGES
IGES (pronounced eye-jess) is a neutral old-fashioned tool primarily used in the defense industry and engineering. It was developed by the US Air Force in the mid-seventies in cooperation with Boeing and others as an interchange format that could be shared between all CAD systems.
Since the 80's, the US Department of Defense has required all defense and arms contracts to use IGES as the standard file format.
The corresponding file extension for the IGES format is .igs or .iges.
Key features of the IGES format:
The IGES format is an ASCII encoding that is very flexible in representing surface geometry. It can store geometry-related information using circuit diagrams, wireframes, precise freeform surfaces, or CSG.
The format can also store colors, but does not support material properties such as textures and material types. Animations are also not supported.
Popularity and future prospects:
IGES has gained popularity since its invention in the 70's. It has been adopted as a national standard by many countries, including the United Kingdom and Australia. Almost all CAD software supports it.
The IGES file format is no longer developed, but is still widely used to transfer data between CAD, CAM, and CAE software programs.
It is a popular choice for 3D modeling, creating technical drawings and product designs. It has been hailed as a good choice for 3D amateurs, although most professional 3D artists now prefer its successor, STEP.
What industries use it?
Defense and Engineering.
6.7 STEP
STEP (Standard for the Exchange of Product Data) or ISO 10303 was developed as a successor to the IGES file format. It is widely used in engineering related fields such as automotive, aerospace engineering and architecture.
The officially stated goal of developing STEP was to create a mechanism capable of describing product data throughout the product's lifecycle, independent of any particular system. However, due to the complexity and size of the original standard, it was later broken down into smaller modular specifications over four major editions.
The corresponding file formats are .stp or .step.
Key features of the STEP format:
The STEP format supports all the features supported by the IGES format. In addition, it can encode material properties such as topology, geometric tolerances, texture, material type and other complex product data.
Popularity and future prospects:
STEP, like IGES, is a popular format for exchanging data between CAD, CAM, and CAE programs. For compatibility, IGES is still recommended as it is the more common format and is more likely to work with the recipient's software. However, for use cases where information related to model appearance, part tolerances, etc. needs to be transferred, STEP is the right format.
What industries use it?
Engineering fields such as automotive, aerospace and construction.
Conversion tools: STEP to STL | STEP to PLY | STEP to OBJ | STEP to GLTF
6.8 VRML and X3D
VRML (pronounced vermal, file extension .wrl) stands for Virtual Reality Modeling Language. It was developed for the World Wide Web and was inherited by X3D.
Spiders3D virtual environment using X3D format
The term VRML was first coined by Dave Raggett in a 1994 paper presented at the First World Wide Web Conference entitled "Extending the WWW to Support Platform-Independent Virtual Reality." It took another three years before the mature version of the format, VRML97, was released. Created and became an ISO standard.
VRML97 was used in some personal homepages and 3D chat sites, but the format failed to gain any significant adoption. Furthermore, the capabilities of VRML have remained stagnant, while real-time 3D graphics have rapidly improved. Eventually, the VRML Consortium changed its name to the Web3D Consortium and began developing a successor to the VRML format, X3D, which was released in 2001.
Main features of the VRML format:
X3D is an XML-based 3D file format. It supports all features of the VRML format plus some additional features.
The VRML format uses polygonal meshes to encode surface geometry and can store appearance-related information such as color, texture, and transparency.
The X3D format adds NURBS encoding to surface geometry, the ability to store scene-related information, and support for animation.
Popularity and future prospects:
X3D aims to be the standard 3D file format for the web. In particular, X3D applets can run in a browser and use OpenGL 3D graphics technology to display content in 3D. X3D is also designed to integrate seamlessly with HTML5 pages, just like the SVG format for images. However, to date, this format has not been widely accepted.
What industries use it?
web application.
6.9 AMF
AMF (Additive Manufacturing File Format) is used to store and describe objects to be processed by 3D printing.
It was launched in 2011 as the 3D printing standard file format by the American Society for Testing and Materials, as a replacement for the widely used current industry standard STL, aiming to address the deficiencies of STL files.
Main features of the AMF format:
- AMF is an XML-based 3D file format. AMF supports everything STL does (ie shape geometry) and is able to store colors, materials and orientations.
- AMF is also a more efficient file format than STL, so more accurate models can be stored without unreasonably bloated file sizes. Additionally, curved polygons can be stored, meaning faces can resemble surface profiles.
Popularity and future prospects:
AMF aims to be the perfect 3D file format for 3D printing, so it has attracted some interest, especially since it is well suited for full-color 3D printing. However, it was never widely used and most people continued to use STL files.
The upcoming 3MF file format is also getting some attention, and if STL loses the top spot in 3D printing, it seems likely that it will replace AMF as the next!
What industries use it?
3D printing, rapid prototyping and computer-aided manufacturing.
6.10 3MF
3MF (3D Manufacturing Format) is an open source project developed by the 3MF Consortium founded by Microsoft. Similar to AMF, 3MF aims to address the shortcomings of STL and become the new standard for 3D printing applications.
3MF logo
Key features of the 3MF format:
- 3MF uses the same compression as ZIP archives, allowing you to store everything an AMF file can, while also saving details such as printer configuration files, manually created supports, G-code commands such as pauses for filament changes, including Thumbnails and modifiers, while taking up less space than STL with only geometry.
- It is also a safer file format for 3D printing, as 3MF files cannot be created with non-manifold edges.
Popularity and future prospects:
Its adoption has been relatively slow, but with some of the bigger players in the 3D printing space showing support for it, more and more 3MF files are being used and shared, and it looks like it will soon replace STL for the top spot.
With the recent popularity of multi-material printing and full-color printing -- made easier to use thanks to Prusa's MMU, mosaic palettes, and other such options -- 3MF seems to have come at just the right time.
What industries use it?
3D printing, rapid prototyping and computer-aided manufacturing.
Original Link: 10 Most Popular 3D File Formats—BimAnt