This is part of the Rendering Tutorial
Let me introduce the pictures I'm about to use to explain my thoughts on how you can easily build a 3D renderer. You can see the picture we'll be using in the following section at your right.
On the left panel, a world view of a scene is depicted, so you can see what's going on in the 3D world while we're trying to display the objects in our world. You can see a very basic house in a 3D world, 3 axes denoting the X, Y and Z axes of our three dimensional world, and a very basic interpretation of what a camera looks like. You can probably figure out that the grayish cube is the body of the camera, the black cube on top of it is the camera's lens, and the line coming out of the camera's bottom is supposed to depict a leg at the bottom of the camera, so we can understand what's up and down from the camera's viewpoint.
In the right panel of the picture you can see what the camera sees, it's a camera view of our world, but I left out the axes and the camera in order to get a good view on our object, the house, we're trying to display. There is no floor in the house, so, as we're looking to the house from the bottom, you can see how the blue roof sits on top of the red walls. If you look closely at the houses in both panels, you can also see that I'm using a dashed wireframe of the house for more clarity in the world view, but I'll be leaving the wireframe out of the camera view as it is not wanted there. And that's exactly what's being done with the camera view.