Virtual 3D camera composition from frame constraints

摘要

We have designed a graphical interface that enables 3D visual artists or developers of interactive 3D virtual environments to efficiently define sophisticated camera compositions by creating storyboard frames, indicating how a desired shot should appear. These storyboard frames are then automatically encoded into an extensive set of virtual camera constraints that capture the key visual composition elements of the storyboard frame. Visual composition elements include the size and position of a subject in a camera shot. A recursive heuristic constraint solver then searches the space of a given 3D virtual environment to determine camera parameter values which produce a shot closely matching the one in the given storyboard frame. The search method uses given ranges of allowable parameter values expressed by each constraint to reduce the size of the 7 Degree of Freedom search space of possible camera positions, aim direction vectors, and field of view angles. In contrast, some existing methods of automatically positioning cameras in 3D virtual environments rely on pre-defined camera placements that cannot account for unanticipated configurations and movement of objects or use program-like scripts to define constraint-based camera shots. For example, it is more intuitive to directly manipulate an object's size in the frame rather than editing a constraint script to specify that the object should cover 10% of the frame's area.