Maya Paint Effects is a module that allows you to paint custom effects directly in your scene. You can paint either in 2D, just like painting on a traditional canvas or you can paint directly within 3D space.
The Paint Effects Panel
Go to Window > Paint Effects to open the Paint Effects Panel. The Paint Effects Panel defaults to the perspective view, but you can switch to orthogonal views by selecting the Camera menu along the top toolbar. The Paint menu allows you to switch between working on a canvas and the current scene.