A unique identifier for each point in a point cloud. If you delete and add points in a cloud, indices may get re-used but the IDs will not.
The ID is automatically set by the Add Point and Clone Point nodes, as well as by compounds that contain them, such as the Emitters and Spawning compounds. You cannot set this attribute manually.
Even though it appears as though this attribute is available for points on objects other than point clouds, it doesn't exist and cannot be set or initialized in those cases.
