In this paper, we describe a novel multifocal projection concept that applies conventional video projectors and camera feedback. Multiple projectors with differently adjusted focal planes, but overlapping image areas are used. They can be either differently positioned in the environment or can be integrated into a single projection unit. The defocus created on an arbitrary surface is estimated automatically for each projector pixel. If this is known, a final image with minimal defocus can be composed in real-time from individual pixel contributions of all projectors. Our technique is independent of the surfaces' geometry, color and texture, the environment light, as well as of the projectors' position, orientation, luminance, and chrominance.

We show how view-dependent image-based and geometric warping, radiometric compensation, and multi-focal projection enable a view-dependent stereoscopic visualization on ordinary (geometrically complex, colored and textured) surfaces within everyday environments. Special display configurations for immersive or semi-immersive AR/VR applications that require permanent and artificial projection canvases might become unnecessary. We demonstrate several ad-hoc visualization examples in a real architectural and museum application context.