A major problem with interactive displays based on front-projection is that users cast undesirable shadows on the display surface. This situation is only partially-addressed by mounting a single projector at an extreme angle and warping the projected image to undo keystoning distortions. This paper demonstrates that shadows can be muted by redundantly-illuminating the display surface using multiple projectors, all mounted at different locations. However, this technique alone does not eliminate shadows: multiple projectors create multiple dark regions on the surface (penumbral occlusions) and cast undesirable light onto the users. These problems can be solved by eliminating shadows and suppressing the light that falls on occluding users by actively modifying the projected output. This paper categorizes various methods that can be used to achieve redundant illumination, shadow elimination, and blinding light suppression, and evaluates their performance. Index Terms — Shadow elimination, blinding light suppression, projector calibration, multiple projector display