The Complete glTF to OBJ Conversion Guide

General Information

This guide is part of the RapidPipeline 3D Formats Knowledge Database. It shows how to convert glTF to OBJ, if you'd like to know more about the formats, please check out the following links:

• Learn more about the glTF format
• Learn more about the OBJ format
• Limitations of a glTF Files to OBJ Conversion Workflow

What are glTF and OBJ files commonly used for?

The glTF file is a format mostly used for interactive 3D, on the Web and elsewhere (e.g., in XR).
The OBJ file is a format mostly used for 3D modeling and generalized 3D applications.

Limitations of a glTF Files to OBJ Conversion Workflow

The following limitations should be taken into account when converting glTF files to OBJ format:

glTF Feature (not supported by OBJ)	Limitation Details
Geometry Compression	Geometry Compression: supported in glTF, but not in OBJ. Geometry compression describes the process of compressing the representations of a 3D model's geometry, usually a triangle mesh. 3D geometry compression does not change the topology of a 3D model, but just changes the way that a 3D model and its 3D positions and related vertex data is stored. Geometry compression can be lossy (just like JPEG compression in image processing can be lossy, for example), in which case one might notice slight artifacts like variations in 3D vertex positions (compared to the uncompressed 3D model). However, such differences are often not noticeable. There are only very few standards for geometry compression, like glTF's support of Draco compression and similar extensions.
Texture Transforms	Texture Transforms: supported in glTF, but not in OBJ. Texture transforms describe transformation operations that are applied to 2D texture images or UV coordinates when using 2D texture data on a 3D surface. They can be used, for example, to make sure that material patterns are using real-world scale when rendered on the 3D surface. In this example, such a pattern is used and scaled with the help of a texture transform. Without support for this feature, the texture pattern shows up at the wrong scale.
Texture Compression	Texture Compression: supported in glTF, but not in OBJ. Texture compression refers to a process of compressing 2D texture images for memory-efficient rendering (and sometimes for efficient transmission). The decompression of compressed texture data is therefore performed on-the-fly during rendering, so that it never has to be stored in unpacked form, but can be kept as-is in GPU memory. Formats supporting texture compression methods, such as the ones offered by glTF through KTX2 containers, therefore allow 3D models to use a smaller memory footprint on the client device during rendering. This can speed up rendering time, and also make it possible to store and use larger amounts of texture data than it would otherwise be possible.
Multiple UV Channels	Multiple UV Channels: supported in glTF, but not in OBJ. Multiple UV channels allow the optimized and sophisticated use of various 3D modeling features at once. For example, one can use one set of UVs and 2D texture data to model a tiling texture or procedural material, and another UV set to leverage a global lightmap or occlusion map of the 3D model. In this example, a combination of tiled texture (UV channel 1) and baked ambient occlusion map (UV channel 2) is used. Without support for this feature, one needs to either give up the tiling property (e.g., by using a tool like RapidPipline to bake a single texture atlas), or give up the ambient occlusion map, as only one UV channel will be usable.
Embedded Textures	Embedded Textures: supported in glTF, but not in OBJ. Embedded textures allow the storage and exchange of an entire 3D model and its materials within a single file, by embedding the texture images directly into the 3D file (and not storing them as separate image files). Without support for this feature, textures have to be stored in separate image files, and referenced from the main 3D model file.
Normal Mapping	Normal Mapping: supported in glTF, but not in OBJ. Normal maps are used to model shading differences that are arising from small geometric details on a surface, such as fabric structures, visible gaps between bricks forming a wall, or rough rock surfaces. In this example, a normal map is used to model a fabric structure. Without support for this feature, the rendered fabric will look smoother than it actually is in the real world, as the fabric structure won't be visible.
PBR Materials	PBR Materials: supported in glTF, but not in OBJ. PBR materials enable Physically-Based-Rendering (PBR) for a standardized, photorealistic look of rendered images. PBR uses concepts like metallic-roughness or specular-glossiness properties and a microfacet-based modeling of the surface, using a concept called BRDF (Bi-Directional Reflectance Distribution Function). In this example, PBR materials are used to achieve realistic looking plastic and metal materials. Without support for PBR materials, only basic colors and shading can be used (for example, based on more simple shading models, such as the Blinn/Phong model).
Vertex Colors	Vertex Colors: supported in glTF, but not in OBJ. Vertex colors allow the attachment of colors to each vertex of a 3D model. This can be useful in scenarios such as scientific visualization, or when converting/meshing data from a colored 3D point cloud, for example. On the polygonal surface connecting the vertices, the respective vertex colors are usually smoothly interpolated. In this example, different colors are attached to the different corners of a cube. Without support for this feature, the cube won't have any colors.
Animations	Animations: supported in glTF, but not in OBJ. Animations are an important part of many interactive 3D assets, for example in real-time rendering (including games, XR training, assembly instructions, product demos, and other use cases). There are various kinds of animations that can be used on 3D models. In this example model, a rigid animation is used to make the gears spin. Without support for this feature, in this example, the gears won't move.
Skinned Animations	Skinned Animations: supported in glTF, but not in OBJ. Skinned animations are commonly used for 3D character models in interactive applications, such as games or virtual worlds. They make it possible to easily animate the 3D model using a helper structure based on virtual bones, composing a virtual skeleton for animation control. In this example, a skinned animation is used to pose a 3D character. Without support for skinned animations, the 3D model will remain in its default pose, such as the default T-pose.
Morph Targets	Morph Targets: supported in glTF, but not in OBJ. Morph Targets, or "Blend Shapes", are commonly used to animate facial expressions and soft surfaces, for example cloth under a cloth simulation. They model various states of the animations with different vertex positions. In contrast to skinned animations, morph targets do not use any virtual bones, but work solely on the vertex data. In this example, a facial animation is achieved through morph targets. Without suport for this feature, in this example, the face will not show the animation.
Rigid Animations	Rigid Animations: supported in glTF, but not in OBJ. Rigid Animations are typically used to animate mechanical parts. In this example, the door of this 3D model of a microwave can be interactively opened or closed, using a rigid animation that gradually changes the 3D transformation of the door. Without support for this feature, in this example, the door will just stay in place and won't move.
Hierarchical Scene Graph	Hierarchical Scene Graph: supported in glTF, but not in OBJ. Scene graphs are one of the most common concepts in 3D computer graphics. By structuring the scene in a hierarchical way, logical parts of it can be easily addressed and transformed. This is useful in many applications, like games or 3D configurators. Without support for this feature, a 3D scene cannot be structured hierarchically, for example objects cannot be logically composed of smaller objects.
Standardized Format	Standardized Format: supported in glTF, but not in OBJ. Standardization plays a huge role in 3D model formats. With a format being standardized, every application will have a clear way of how to load or store data using this format. This makes it easier to re-use the 3D model across different applications, but also to make sure it will still be accessible and usable after a couple of years.

Converting and Optimizing glTF Files to OBJ

There are various ways to convert between glTF and OBJ. With RapidPipeline, you can easily convert and and optimize glTF files, at scale. It supports OBJ, as well as many other file formats (examples: 3dsMax, FBX, PLY, STEP, STL, USD, USDZ, VRM), at high quality.

Due to the potential limitations aforementioned on the table above, in principle, one cannot always perfectly convert 3D data between OBJ and other formats. In the following, you can find conversion guides between OBJ and the most important other formats, along with a rough score for compatibility of this workflow:

What's the best way to get glTF files into my 3D applications, and are there alternatives to using OBJ?

Doing 3D conversion right, especially at scale, can be tricky, as 3D data is in general a rather complex (yet very powerful!) medium. This also applies to glTF and OBJ files - the conversion guide above provides a rough first idea about that. Once you know what you would like to do, tools like RapidPipeline can help you perform the necessary steps, and to even automate the process for thousands or even millions of files.

Especially when introducing pipelines and workflows at scale in an enterprise context, it is usually good to rely on dedicated tools and expertise, making sure you do not introduce any steps into your 3D workflow that are detrimental to the final output's quality, or that take your team too much time (and money).

If you're interested to hire dedicated expertise from the best in the field to help your company reach your goals fast and reliably, please do not hestitate to contact DGG. Being the creators of RapidPipeline, and ambassadors for open 3D standards for more than a decade, we have been building some of the world's most advanced 3D pipelines, having processed many millions of 3D assets.

Therefore, our expertise will help you to reach your goals faster, at scale, and with the least possible friction, since we are focused on maximum interoperability.

To get started with 3D data conversion and optimization today, sign up for a free account!

If you have any questions, feel free to chat with our human team.