  Since their introduction more than two decades ago, light fields have gained
considerable interest in graphics and vision communities due to their ability
to provide the user with interactive visual content. One of the earliest and
most common light field operations is digital refocus, enabling the user to
choose the focus and depth-of-field for the image after capture. A common
interactive method for such an operation utilizes disparity estimations,
readily available from the light field, to allow the user to point-and-click on
the image to chose the location of the refocus plane.
  In this paper, we address the interactivity of a lesser-known light field
operation: refocus to a non-frontoparallel plane, simulating the result of
traditional tilt-shift photography. For this purpose we introduce a generalized
shift-and-sum framework. Further, we show that the inclusion of depth
information allows for intuitive interactive methods for placement of the
refocus plane. In addition to refocusing, light fields also enable the user to
interact with the viewpoint, which can be easily included in the proposed
generalized shift-and-sum framework.
