Stephen,
What you are looking for here is projection-mapping. You can do it manually – especially if you have a single projector, but if you want to create masks and simulate multiple surfaces you should really be looking at a projection-mapping application that allows you create masks, surfaces etc. By having multiple surfaces you can have different sources playing onto each surface. The surfaces can all be displaying on the same area – but you could for example, have your background on surface 1, then have an animation on surface 2 etc..
If you have apple – madmapper or GrandVj are two applications that spring to mind – GrandVJ also support windows.
Manually will be very, very time-consuming… I tried it and gave up – have been playing with GrandVJ for a while now – V2 has it built in.
Just one point to note – at 150ft – even indoors you will need a decent projector. For example (and I know it is a totally different situation) – the ‘India gate’ projection referenced in Abhi’s post used 4 x 22000 (yes 22K) lumens barco projectors..
At 150′, any standard lens will create an image so large it will be almost invisible even in very low-light. You will need a projector with a long-throw lens, and at 150′ it will need to be bright – I don’t believe many of the conventional consumer projectors would work satisfactorily from that distance.
For example, a Panasonic PT-DW6300US at 150′ throw will create an image of approx 25′ diagonal. That device pushes out around 6000 lumens, and costs around €5000… I would certainly recommend renting something decent.
There maybe more informed people on the forum here – I am only a hobbyist, but these are my experiences…
Stewart