ol.layer.AnimatedCluster is a layer that animates clusters on zoom change.
The layer is created with an ol.source.Cluster as standard cluster vector layers.
ol.interaction.SelectCluster is a select interaction. On select cluster springs apart to reveal the features. The revealed features are themselves selectable. Revealed features are themselves a cluster with an attribute 'features' that contain the original feature.
The example uses the convex envelope calculation to draw a polygon around the points of the cluster (see ol3-ext convex hull example).