This sample demonstrates usage of the EXT_structural_metadata extension for storing a property table with metadata that is looked up based on feature IDs.
The sample uses the EXT_mesh_features extension for storing feature IDs that are associated with vertices of a mesh. The basic structure and definition of the feature IDs for this example is the same as for the FeatureIdAttribute example.
Additionally, this sample defines metadata that is associated with the feature IDs.
The structure of the metadata is defined with an EXT_structural_metadata schema that contains a single class. The class only contains a single property, called example_VEC3_FLOAT32. The type of this property is a 3D vector with 32 bit floating-point components, as indicated by the type "VEC3" and the component type "FLOAT32".
The metadata entities are the actual instances of this class. They are defined with an EXT_structural_metadata property table. The rows of this table correspond to the feature IDs. The columns of this table correspond to the properties of the class. The data for each column is stored in a standard glTF bufferView.
Based on the type information from the metadata class, the contents of this buffer view is interpreted as four 3D vectors with 32 bit floating point components:
"example_VEC3_FLOAT32" : [
0.0, 0.1, 0.2,
1.0, 1.1, 1.2,
2.0, 2.1, 2.2,
3.0, 3.1, 3.2
]
This example can be viewed with the common sandcastle code.