Format of the mesh index buffer data.
Index buffer can either be 16 bit (supports up to 65535 vertices in a mesh), or 32 bit (supports up to 4 billion vertices).
Default index format is 16 bit, since that takes less memory and bandwidth.
Note that GPU support for 32 bit indices is not guaranteed on all platforms; for example Android devices
with Mali-400 GPU do not support them. When using 32 bit indices on such a platform, a warning message will be
logged and mesh will not render.
Note: the maximum possible vertex index (for example, 0xFFFF for a 16 bit index format) might not be usable. Some graphics APIs and GPUs skip rendering triangles with maximum vertex indices.
Changing indexFormat sets subMeshCount to one and clears the index buffer.
Refer to Mesh.MeshData.GetIndexData for an example.
Additional resources: IndexFormat, ModelImporter.indexFormat, SetIndices, SetTriangles, SetIndexBufferParams, SetIndexBufferData, MeshData.