A system comprising: a first projector configured to project a first projector image; a second projector configured to project a second projector image stacked onto the first projector image, the first projector image and the second projector image initially out of alignment; at least one sensor configured to acquire a first image of the first projector image and a second image of the second projector image; a computing device in communication with each of the first projector, the second projector and the at least one sensor, the computing device being configured to: determine, in a common space, respective initial positions of each of the first projector image, from the first projector image, and the second projector image, from the second image; determine, in the common space, a virtual projector image, the virtual projector image located at a common target position, in the common space, for the first projector image and the second projector image; determine respective transforms for each of the first projector image and the second projector image to one or more of shift and transform each of the first projector image and the second projector image to the common target position of the virtual projector image; apply the respective transforms to each of further first projector images and further second projector images to respectively produce transformed first projector images and transformed second projector images; and, control each of the first projector and the second projector to respectively project the transformed first projector images and the transformed second projector images according to the common target position, the system being characterized in that the computing device is configured to, when determining the virtual projector image, use a continuously adjustable parameter to locate the virtual projector image at the common target position, the common target position being at a position at or between said respective initial positions in accordance with said continuously adjustable parameter. a first projector configured to project a first projector image; a second projector configured to project a second projector image stacked onto the first projector image, the first projector image and the second projector image initially out of alignment; at least one sensor configured to acquire a first image of the first projector image and a second image of the second projector image; a computing device in communication with each of the first projector, the second projector and the at least one sensor, the computing device being configured to: determine, in a common space, respective initial positions of each of the first projector image, from the first projector image, and the second projector image, from the second image; determine, in the common space, a virtual projector image, the virtual projector image located at a common target position, in the common space, for the first projector image and the second projector image; determine respective transforms for each of the first projector image and the second projector image to one or more of shift and transform each of the first projector image and the second projector image to the common target position of the virtual projector image; apply the respective transforms to each of further first projector images and further second projector images to respectively produce transformed first projector images and transformed second projector images; and, control each of the first projector and the second projector to respectively project the transformed first projector images and the transformed second projector images according to the common target position, determine, in a common space, respective initial positions of each of the first projector image, from the first projector image, and the second projector image, from the second image; determine, in the common space, a virtual projector image, the virtual projector image located at a common target position, in the common space, for the first projector image and the second projector image; determine respective transforms for each of the first projector image and the second projector image to one or more of shift and transform each of the first projector image and the second projector image to the common target position of the virtual projector image; apply the respective transforms to each of further first projector images and further second projector images to respectively produce transformed first projector images and transformed second projector images; and, control each of the first projector and the second projector to respectively project the transformed first projector images and the transformed second projector images according to the common target position, the system being characterized in that the computing device is configured to, when determining the virtual projector image, use a continuously adjustable parameter to locate the virtual projector image at the common target position, the common target position being at a position at or between said respective initial positions in accordance with said continuously adjustable parameter.