The shadow of an occluder obstructing the projection surface is responsible for decreasing the efficiency of the projection system. The situation becomes critical when there is no option to place the camera between the occluder and the projection surface. Such a situation calls for installing multiple projection systems over the same projection surface. The authors present a technique that employs multiple overlapping projection systems to remove the shadow of the occluder.

This technique estimates the projection surface and occluder shape measurement in order to remove the shadow of the occluder in a projected image. This shadow removal technique employs multiple overlapping projectors and cameras that estimate the projection surface by synthetic aperture capturing and visual hull reconstruction. Synthetic aperture capturing measures the projection surface and estimates an approximate shape measurement of the occluder. The authors apply the visual hull technique to “obtain the shape of an object as an intersection of multiple silhouettes captured from different positions.” This enables the extraction of object silhouettes from the background surface providing 3D information for the occluder.

For experimentation, the authors use four projectors and five cameras, connected and controlled by a PC. The authors provide an extension in the shadow removal technique to balance the visibility of the projectors, the likelihood of new shadow emergence, and the spatial resolution of projected results.

The performance of a multiple overlapping projection system depends on the way it detects the occluder and removes its shadow. The synthetic aperture capturing and visual hull reconstruction techniques to remove the shadow of the occluder make the paper worth reading.