3D screen-space widgets for non-linear projection

Abstract

Linear perspective is a good approximation to the format in which the human visual system conveys 3D scene information to the brain. Artists expressing 3D scenes, however, create nonlinear projections that balance their linear perspective view of a scene with elements of aesthetic style, layout and relative importance of scene objects. Manipulating the many parameters of a linear perspective camera to achieve a desired view is not easy. Controlling and combining multiple such cameras to specify a nonlinear projection is an even more cumbersome task. This paper presents a direct interface, where an artist manipulates in 2D the desired projection of a few features of the 3D scene. The features represent a rich set of constraints which define the overall projection of the 3D scene. Desirable properties of local linear perspective and global scene coherence drive a heuristic algorithm that attempts to interactively satisfy the given constraints as a weight-averaged projection of a minimal set of linear perspective cameras. This paper shows that 2D feature constraints are a direct and effective approach to control both the 2D layout of scene objects and the conceptually complex, high dimensional parameter space of nonlinear scene projection.