@ Brian Kim (3/14/2023)

OBJ

About

These are the most commonly used 3D file types, created by Wavefront Technologies in the 1980s, and any 3D model user should be familiar with this file type. For instance, it is the most popular file type on Free3D.

Pros

• Default 3D model, widely used and accepted by pretty much any software, including Blender and Unity

• Very flexible, uses a text-based language instead of a binary language

• Can store unlimited colors

Cons

• Usually larger than other file types due to using a text-based language

• Very expensive and time-consuming for high-quality rendering and modeling

• Cannot store information about animations or skins

• Cannot easily store information about subcomponents and submeshes

FBX

About

FBX files were designed to be used with a film capture tool made by Kaydara in 2005, but have since become one of the most popular and best-suited file types for high-end gaming rendering, working particularly well with Unity. This is my recommended format for students working with Unity.

Pros

• Extremely detailed, can include skins, animation data, bones, scene hierarchies, lighting, material attributes, etc.

• Capable of heavy complexity, including multiple topologies and subdivided surfaces

• Relatively fast file format using binary code

• Easily integrated with official Software Development Kits (SDKs)

• Works well with CAD files like STEP, can more safely transfer NURBS data to FBX formats (see entry on STEP)

Cons

• Closed file format that only works with official SDKs, not usually a problem with Unity or Unreal Engine but could be in other contexts

• Some of the standards used by FBX are becoming outdated, so some files might need rerendering

• Not as fast as some newer file types

gITF

About

gITF stands for GL Transmission format, and is a close competitor with FBX for the most popular model type in sophisticated modeling. It is open source and was first developed by the Khronos collective in 2015, and it was designed to act as a lightweight 3D file format for the web and web browsers.

Pros

• Maximizes web browser compatibility and is kept up to date by developers, in contrast to FBX

• Huge speed and size advantage, in particular much smaller and faster to read than OBJ files

• Optimized to handle animations

• Overall, extremely well-suited for web-based AR and VR experiences

Cons

• Can suffer from image quality issues, not preferred for gaming or special effects

• Lack certain features that FBX models contain, such as shader networks

• Not optimized for CAD and other 3D printing systems, so difficult to convert with STEP models or similar file types

usdz/usd

About

USD and USDZ files were originally developed by Pixar for their animated films and were subsequently picked up by Apple for their AR software. USD stands for Universal Scene Distribution and the "Z" in USDZ just indicates that the file has been zipped.

Pros

• Cutting edge of 3D modeling in terms of detail and render quality, particularly for ultra-realism

• Can store models and images with multiple topologies, creating more detailed surfaces and realistic lighting situations

• Extremely fast processing speed

Cons

• Only works on software programs made by Apple and models only run properly on Apple machines

• Not backwards compatible with older standards, such as OBJ

• Files produced with this standard are usually extremely large and expensive to handle

Blender

About

Blender is an open-source modeling and animation software maintained by the Blender Foundation. It uses its own file type, .blend, to store information about scenes and projects, which can be imported into Unity and certain other VR development softwares. However, I recommend instead exporting scenes as a direct model in a specific model format before pulling the objects into Unity or a similar setup.

Pros

• Directly integrated with Blender, a popular free modeling and animation choice

• Capable of holding a great deal of information, due to being designed to contain entire scenes

• Supports a workflow from Blender directly to a VR development software

Cons

• Due to the need to keep scenes editable, .blend files are quite large and not optimized for space

• Can be computationally expensive to import .blend files rather than more specialized model file types

STEP

About

STEP (Standard for the Exchange of Product Data) files are designed for CAD modeling, and in that area, are one of the most successful file types. These files might come up for VR developers if they are looking for specialized models online, but they should know that these are not designed for 3D graphics and will probably have to be processed through Blender into another file format before going into a system like Unity.

Pros

• Will be the preferred file type if downloading specialized models from CAD workshops or databases

• Instead of a polygon system, uses mathematical functions called NURBS to store data, making STEP models extremely precise

• Thanks to NURBS, can also store extremely smooth and complex 

Cons

• Can only contain data about shapes, cannot hold information about texture or color

• Because it was made for CAD, it is usually impossible to use the files directly for 3D modeling

• Converting the file into polygon-based formats, such as using Blender, can lead to distortions as well as extra work