Rigging is the process of connecting a mesh with an internal poseable skeleton rig and bone structure. Rigged meshes allow mesh surfaces to rotate and move where internal bones are placed within the model during the modeling process. Rigging is often performed in conjunction with skinning, creating a natural looking stretch and bend when models are animated or repositioned. You can create rigged meshes with third-party software such as Blender or Maya.
See the following resources to learn the basics and intermediate steps required to skin models in Blender:
The rig, or bone structure, within a rigged mesh creates additional posable points for the 3D model in Studio. By rotating or moving the bones of a mesh, the parts of the mesh assigned to those bones can move independently from the rest of the mesh. The assignment of influence between meshes and bones, such as a LowerLeftArm bone driving the movement of the LowerLeftArm geometry, is set in a third-party application like Blender or Maya. When imported into Studio, Roblox saves this influence assignment data to the MeshPart asset data.
Once you successfully import a rigged mesh model into Studio, Studio represents this rig structure with Bone instances that you can then pose and animate. You can view bones in Studio by toggling Constraint Details in the Model tab, or when you are using the Animation Editor.
Rigged models use a naming convention starting with "R" and ending with the number of individual meshes that make up the model. This is used to quickly identify the type and number of meshes that a model has. Although R6 and R15 models are common, a model can be of varying subjects, sizes and can have any number of individual meshes, such as a R5, R20, or R200.
R1 refers to a single mesh that is rigged, or associated with an internal skeleton structure. Many models, such as a tree or accessory item, are good candidates to be made into an R1 model. Even humanoid characters, such as NPCs, can be created as R1 models but they will not be able to take full advantage of the animation and humanoid options available for R15 characters.
See Rigging a Simple Mesh for instructions on turning a basic mesh into an R1 model in Blender.
R15 typically refers to humanoid models used as player or avatar characters. An R15 model is made up of 15 specific meshes that are parented to a single rig. A R15 character model often includes skinning data to allow the model to bend and pose naturally. Roblox uses the R15 standard for all avatars, and requires the R15 technical specifications to ensure universal behavior and quality.
See Rigging a Humanoid Model for instructions on turning a character model into an R15 humanoid model in Blender.