Blender to Roblox: Which Format, OBJ, FBX or GLTF?

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Both Blender and Roblox Studio use the same scaling to define their base units of measurement, metres. This ensures objects exported from Blender are the exact same size in Roblox Studio. However, depending on the format used, OBJ, FBX or GLTF (GLB), models may appear incorrectly scaled, a pain-point for productivity that raises questions on how best to make models for export from Blender to Roblox Studio, and what mesh (file) format to use.

OBJ vs. FBX vs. GLTF

The three main mesh or model formats Roblox can import and use are; OBJ, FBX and GLTF (GLB).

OBJ

OBJ (Object) files are safe for static, non-animated objects or environment pieces as they’re a low overhead text-based format that’s mesh-specific. Data typically exported include mesh, UV, vertex colours, textures, and PBR materials to a limited degree.

FBX

FBX (Filmbox) files can be used for both static and animated objects, characters, environment pieces or other content. Data that’s typically accommodated includes mesh, UV, vertex colours, textures, and PBR materials. Along side this, both skeletal (Armature) and morph (Shape Key) animations can be included.

GLTF

GLTF (Graphics Library Transmission Format) can be used for both static and animated object, characters, environment pieces and other game content. Data typically includes mesh, UV, vertex colours, texture, and PBR materials. Alongside this, both skeletal (Armature) and morph (Shape Key) animations are supported.

Design note: export limitations… [more]
While each format is subject to different limitations and capabilities, they can all be augmented in Roblox Studio to create effects or animations not otherwise exportable from Blender. For example, OBJ models cannot be animated in Blender but can in Studio, when included as part of a game object or entity that creates an editor specific effect or action. The same is true for FBX and GLTF, models can be bound to game objects, which are further enhanced by the ‘animated’ element exported from Blender.

Which Format is Best

In practice, OBJ, FBX and GLTF perform equally well for MESH data, so usage is largely down to availability, familiarity or workflow preference rather than strict utility. For ANIMATED objects and content, FBX and GLTF perform much the same from a workflow perspective. However, because FBX is a much older format its more broadly available than GLTF but lacks support for more modern data types or complex structures.

Important: FBX scaling issues in Roblox… [more]
FBX is subject to scaling issues when used for Roblox content creation – on export of an FBX from Blender, or importing and FBX into Roblox, be sure to set the ‘Scale‘ value to 0.01 to properly compensate for the size difference.
Design note: types of relational skeleton… [more]
Both FBX and GLTF files can export bone-based or object-based skeletons, that is, skeletal structures made exclusively from Armature objects, structures made from objects that form a ‘skeletal relationship’, or a combination of the two. In all cases, Armatures, nodes (Empty’s) and mesh objects, can be linked through a Parent » Child relationship that forms a structure that accommodates the conditional manipulation or animation of an object or objects in Roblox.

Animated object in Blender
A simple game object configured for animation using an Armature in Blender.

Export format for Roblox
For static content like accessories OBJ, FBX and glTF are functionally the same. For animated or more complex items FBX, or preferentially glTF, should be used.

Object Size

For Roblox content creation, objects should be made at-scale in Blender, that is, the size they need to be in Roblox. As both applications use the same underlying units of measurement, models should appear the same size/scale in Roblox Studio as they do in Blender – a 1 x 1 x 1 cube should be the same size regardless. While Blenders grid and Unit properties can be tailored to Roblox, the defaults function just as readily for proper scaling. Alternatively, for more accuracy, or for a better fit, reference objects can be exported from Roblox and imported into Blender for scaling, either a Part that’s a defined size (e.g. 1 x 1 x 1 block), or an R6 or R15 character base (mesh export only).

Design note: which Roblox avatar to use… [more]
The default character used in-game is based on either the Mesh Avatar (2012) or Mesh Avatar (2016), so these should be used for general scaling unless there is a specific need or experience content is being made for. To do this, from the Home or Avatar tab, click on the Charactericon. In the Generate Rig popup set the Rig Type, Body Shape, then click an available ‘Avatar‘ option below – My Avatar, Skinned Avatar, etc. Once in the scene, from the Explorer, right-click the instance and select Save/Export » Export as OBJ/Export as glTF. The same process can be done for Part objects (meshes).

Roblox base character export
Exporting a base character from Roblox to use as a size/scale reference in Blender.

Model at size in Blender
When making content for Roblox in Blender, as they both use the same unit of measurement, model ‘at scale’ as they obejct should appear in-game.