1. A method for determining a rectangular area with a given aspect ratio within a global boundary formed on a projection surface by multiple projectors, the method comprising: repeatedly performing an iterated process at moved locations along the global boundary until a stopping condition has been met, wherein the iterated process comprises: selecting a point at a location of the global boundary, identifying directions aligned with a minimum rectangle positioned at the selected point in which the minimum rectangle with the given aspect ratio can be grown from the selected point, wherein for each such direction: growing the minimum rectangle with the given aspect ratio in the direction from the selected point until it intersects with a boundary of the global boundary, determining whether the grown rectangle can grow in another direction responsive to the grown rectangle intersecting with the boundary of the global boundary, growing the grown rectangle in the other direction responsive to a determination that the grown rectangle can grow in the other direction, comparing the grown rectangle with a largest rectangular area encountered previously, and replacing the largest rectangle encountered previously responsive to a comparison which indicates that the grown rectangle is larger than the largest rectangle encountered previously, wherein the method further comprises: delivering the largest rectangle encountered responsive to a determination that the stopping condition has been met.