This Eucalyptus in glass vase is combination of three dimensional vase and water, but the Eucalyptus it self is texture on plane. For this reason the object should be always directly facing the camera.
Second plane is invisible to the camera, but it casts shadows in scene where the light is coming from the side.
This 3D model is ideal for still images and scenes with lowpolygon count. Very closeup scenes might reveal the 2D plane, but when the camera is one meter or more away from the object it looks totally real.
Great thing also is that the vase and water are 3D, because this always makes sure that the object is in right perspective which is a problem when adding similar object in post processing.