A game can be roughly divided in 3 parts:
- common logic
Reusable stuff that you bought, downloaded, or programmed yourself. This could be a complete engine, or at least standard libraries such as DirectX/OpenGL(3D graphics), Newton(physics) or FMOD(sound). Although the borderline is vague sometimes, this part should be isolated from the actual game more or less, meaning it can be reimplemented in another game, as it does not contain specific rules or restrictions.
- game logic
This part tells how the actual game is played. Game rules, how to control the "player"(whatever that is), when to win or lose, enemy AI, et cetera. It's based on what the common logic provides you, so the implementation depends on it as well. It could be just some more code in the same application. But also DLL's or script files.
3D models, 2D textures, animations, audio, game maps, and everything else you could load from a disc. Usually these assets are made by the artists, and loaded into your game depending on the game-mod, current level or current location the player is.
>> Is it part of the Engine features? Or is everything programmable?
That really depends. If you program your own game or game-engine, then of course everything is programmable. In that case, you are responsible for rendering ("drawing") your 3D stuff, as well as for loading the resources (image, animation and 3D model files). When using an engine, those functions are likely done for you. Though you still have to tell which files to load, or what drawing options are used to render something. As said, its really different for each approach, although the raw basics are the same.
As for your 3D example. This is how I would do it:
1- Artist makes a 3D file in Max, Maya, or whatever
* This contains: the 3D model itself, one or more textures(images) applied on that model, some animations eventually
2- Some editor or convertor tool provided by the engine, or self-made, will convert the Max/Maya/Image/xyz/ file to our own internal format
* This internal format is basically the same, but is assured to contain everything we need in our game, and loads fast.
3- In another map-editor, I place this 3D object I just imported into a map. So, an instance of this object is placed at a certain location. This is saved within the map data.
4- Now when playing the game, the engine loads the map files, and creates those object instances I made in step 3.
* This creation basically means that I'll make usable "objects" in engine & computer memory. An object for the map(s), an object for the player, objects for enemies, decodations, audio fragments, textures et cetera
* The engine knows what to do with those objects. How to play them, or how to draw them in case of visual objects.
* Visual objects are usually a bunch of vertices & triangles (a "mesh"), linked to a material (textures & shader) and maybe some animation. All this data is available in the computer RAM and/or videocard memory now.
5.- X(60?) times per second, the engine draws everything you should see.
* This is based on the loaded resources, how the graphics pipeline in the engine was made, shaders, and the underneath rendering API (OpenGL, DirectX, ...)
>> Who does this?
Someone who can draw textures, someone who can model 3D meshes, and someone who can code its own engine or at least knows how to use an existing engine. Look at any game "credits" screen.
>> How can it be done?
>> Is it too hard?
Hard? Yeah, I'm programming 13 years and still don't know half of it. But you don't have to start with super advanced things of course. What is your role in this? Are you a programmer? Ifso, just start with some basic programs. Tons and TONS of OpenGL / DirectX demo's that show you how to setup a first drawing screen.
Or, another route is to start editing existing games. Just make your own map in Halflife Source, Unreal UDK or CryEngine Sandbox. You don't have to code anything, but you get in touch with very typical game engine design. How a map is made, what kind of resources are needed, and in which programs to make them.
>>What does it take to accomplish such task?
Patience my friend. And a lot of love for the subject. If your goal is to quickly create something to earn some cash or whatever, then forget about it.