Here is an awards show from a recent meeting. The screen was over 80′ wide and was run from a single PPT computer (with a backup computer inline as well).
To do this and keep really high quality display, the screen uses three slightly overlapped projectors – 3 blend projection. There is a lot of specialty equipment between the PPT computer and the projector. But getting there creates a smooth, single image. If you look at this image, you can see the three projector fields (this is before the projectionist adjusted the levels to make all uniform).
– Troy @ TLC