There have been a lot of requests for a tutorial of a basic Maya multi projection setup for matte painting. This is not a glamorous example of projections but I was going for simple and clear in order to teach the setup. I put this setup together a while ago and you can see a little of my frustration coming out with the way Maya does projections. The biggest problem with Maya projections is the complexity of the set up and Maya not giving good feedback if something is set up wrong. A lot of times if something is broken Maya does not give any ques of what is wrong--I guess that describes how Maya works in a lot of ways (arg!).
Here is the scene in Maya. On the left is a UVed obj that I based the projections from. The center is a multi projection setup of the same image. On the right there is a purple dot projection for you to test your knowledge. You can mess around with the file and see if you can understand how it was put together. And here is my challenge to you: take the purple dot and add it to the main (center) projection set up. Check it out and see if you can do it.
I can add here that I think it is quite strange but there is very limited resources on how to setup projections in Maya out there and to my knowledge this is the only one of its kind. So enjoy.
Here is the node graph in the hypershade.
Here is a render of the objs and a view of the alpha. Notice I have it set up that the projection is cutting out the alpha.