I'm working on creating a set of 3D landscaped tectured and lit to appear 2D for a project, and i'm running into a little confusion.

This is the scene as it appears in the perspective and camera veiws. The only lighting is an ambient light.
However, this is the same scene in render veiw and as rendered.

Notice that there now appears to be shading, as if the scene is now using the default lighting? This persists when using all other methods for mental ray including mental ray, and i have no idea how to alter it. any suggestions?