This sample demonstrates usage of the EXT_mesh_features extension for storing feature IDs for vertices of a mesh.
The sample contains a glTF asset with a single mesh primitive. The mesh primitive consists of 4 quads (each formed by 2 triangles). The vertices in this mesh primitive have the usual POSITION and NORMAL vertex attributes.
Additionally, each vertex has a feature ID. In this example, the feature ID is given by the _FEATURE_ID_0 attribute of the mesh primitive. This attribute refers to a standard glTF accessor with type "SCALAR" and component type UNSIGNED_BYTE, so that each vertex is associated with one UNSIGNED_BYTE value as its feature ID.
The following image shows the mesh primitive with its vertices, their indices, and their feature IDs:
This example can be viewed with the common sandcastle code.