Gabe Newell: The railings are models. We call them static props. Static props are LOD'd and culled by area portals. They are created in a modelling package (we use XSI primarily). They light just like the world. Most of the time you think of them as world geometry with attractive performance characteristics that you probably build in XSI. If you were building something very complex, say a domed and engraved roof with really intricate detail, you would probably use a static prop.

Gabe Newell: Not in the first release. It's a feature our partners have asked for, in addition to the level developers.

Gabe Newell: We continue to have a mix of GUI and command-line tools. Face Poser is a new tool for building character performances. Given what you do with it, it has to have a GUI. For something like sprgen, given our work-flow, it didn't occur to us that a GUI would really be necessary or all that useful.

Gabe Newell: Probably not, for the reason you suggest. Before hacking got so annoying, we would have done it, but now the positives for developers is swamped by the negatives for players.

Gabe Newell: Materials are described in text files, but that's pretty much where their resemblance to Quake 3 shader definitions end. For example physics properties are also included in VMT files, whereas shader algorithms are not. Source materials are scalable, whereas Quake 3 materials are not. And so on.

Gabe Newell: Yes, there are sprites. Yes, they are more advanced (you can select a VMT to use as a sprite). In many cases where you used to use sprites you would now use something else (e.g. per-pixel lit particles).

Gabe Newell: We use a combination of dynamic and static lighting. Objects that move cast dynamic shadows whereas static objects cast, well, static shadows that are cheaper. On DX9 you get soft dynamic shadows as well. We also have a full radiosity solution for static bumped lighting (bump maps work with static lights). If you were to put a static light next to a bump-mapped object, the light direction would be correct (traditionally light maps and bump maps have been mutually exclusive).

Gabe Newell: Sure. You could build your helicopter out of brushes or props, build your doors out of brushes or props, have everything lit correctly, have hierarchical structures, etc...

Gabe Newell: About half.

Gabe Newell: Because we are teasing you.

Gabe Newell: Do not shoot the G-Man. Bad bad idea.

Gabe Newell: Yes (rain, fog, snow ...). Weather effects are traditionally implemented with a combination of sprites, particles, screen space effects, detailed props, and these sub-systems will make it very easy for MODers to either use our weather effects, modify our weather effects, or create their own. Weather gets more interesting when you start tying it to game logic and physics - for example one of the developers built a mini-tornado that not only looked like a tornado, it would push the player around, and pick up everything that was light enough and swirl it around.

Gabe Newell: Say hello to my little ichthyosaur ;-)

Gabe Newell: At points in the game there are teleports and monsters will use them.

Gabe Newell: Sure.

Gabe Newell: How come no one ever asks about hedgehogs. Hedgehogs are pretty darn cute if you ask me, and they eat slugs, which in the Pacific Northwest is a total bonus feature.

Gabe Newell: That's a good idea.

Gabe Newell: You don't see your hands when you are driving and you don't see your feet pretty much ever.

Gabe Newell: The G-Man is actually a hermaphrodite. Don't tell anyone ;)

Gabe Newell: That's pretty much all they sell at the Gap in the future :)