How would you define the difference between these three. The Engine is the complete package for example, it has everything, graphics, sound, physics, AI, particles ... The level editor is a substantial program also however. How is the level editor such as Hammer/Radiant, different to say Maya/3D Max, and how is the rendering different(if it is) from the actual Game Engine. For example in a level editor, you load your pre-made models/terrain that you made in say Maya, you then drag and drop these models into the level design grid, you can add effects such as lighting or physics effects, you can add sounds points, and various other effects. When you create a level you then save/export this data to some format, either custom, or a more accepted standard such as Collada, obj, xml or just a text file with ascii values. The engine then loads these files, parses through them and renders the data.

So as I said the lines between say Maya and Hammer must be pretty blurred in a lot of areas, essential level editors are similar to modelling software, is this correct.

I am really trying to understand the architecture of a level editor.

Usually the game engine contains subsystems that the game can use. Many times it reads in text files that define what resources to load. Aside from that it also lets you code new features without doing everything from scratch.

A level editor is used to create levels. That's it. Most times you can place objects, adjust properties and export this information to a resource file the engine is able to load. A property of an object could be the model to give it. The level editor is very different from the game engine. It doesn't contain gameplay, and usually the renderer isn't great. A level editor doesn't even have to render anything. You could technically even use a text-based UI to create the level... Some level editors however actually use the rendering subsystem of a game engine to preview some effects.

The model editor is creates the models. You don't set the positions inside a level or anything like that. Most level editors don't have a model editor build-in, so you will need to create models using a model editor. I don't understand all your questions, but rendering a model inside a model editor is very different than rendering from a game engine. The game engine is made for real-time rendering, the model editors renderer is probably not.

If you want to get down to it a level editor -is- similar to a modeling program in that it is just outputting vertex data for you to render. That said, game editors can be a lot of different things. Hammer is about as close as you would get to a model editor since the levels are built with brushes and are basically hand placing geometry, on top of that you add in things like entities and other objects.

But keep in mind that those editors tend to output a lot of data besides just geometry, depending on the tool and engine an editor might output seperate files related to npc placement, triggers, links to scripts, all kinds of game specific data which may either be in different files or could even be built into the map data file if it uses a data format that suits it.

Also not all editors are like hammer, think of an editor for an RTS or something, or for building areas in an MMO, or an rpg even. Some editors don't stick to geometry placement like hammer does, they may have you morphing terrain with different tools or placing models like buildings and doors and things, it entirely depends on how the tool(s) are set up.