A growing body of research is investigating the use of tabletop displays, in particular to support collaborative work. People often interact directly with these displays, typically with a stylus or touch. The current common focus of limiting interaction to 2D prevents people from performing actions familiar to them in the 3D world, including piling, flipping and stacking. However, a problem arises when viewing 3D on large displays that are intended for proximal use; the view angle can be extremely oblique and lead to distortion in the perception of the 3D projection. We present a simplified model that compensates for off-axis viewing for a single user and extend this technique for multiple viewers interacting with the same large display. We describe several implications of our approach to collaborative activities. We also describe other display configurations for which our technique may prove useful, including proximal use of a wall or multiple-display configurations.