In most projects an architectural visualization artist will try to simulate sunlight on both external and internal visualizations for architecture. If the project is an internal view the sunlight will get into the room mostly through a window. An interesting tutorial created by an artist called Jason Clarke show how to create a simple room with a window, and make the sunlight to get into the room through the window. All of that using Blender and LuxRender for the final render. In the tutorial below you will learn some basic, but important concepts about LuxRender like light setup and how to work with portals.
If you want to learn how to create a scene and render it with LuxRender from scratch, I strongly recommend you to watch this tutorial:
Very nice. Great quality, very informative with great results. Thank you for your time in putting this together, I am inspired.