Q1: What is MegaTexturing technology?

John Carmack: MegaTexture technology is something that addresses resource limitations in one particular aspect of graphics. The core idea of it is that when you start looking at outdoor rendering and how you want to do terrain and things in general, people almost always wind up with some kind of cross-fade blended approach where you tile your textures over and blend between them and add little bits of detail here and there. A really important thing to realize about just generally tiling textures, that we're so used to accepting it in games, is that when you have one repeated pattern over a bunch of geometry, the texture tiling and repeating is really just a very, very specialized form of data compression where it's allowing you to take a smaller amount of data and have it replicated over multiple surfaces, or multiple parts of the same surface in a game since you generally don't have enough memory to be able to have the exact texture that you'd like everywhere.

The key point of that is what you really want to do is to be able to have as much texture as you want to use where you have something unique everywhere. Now normally, you just can't get away with doing that, because if you allocate a 32,000 by 32,000 texture, the graphics curve can't render directly from that. There's not enough memory in the system to do that, and even when you have normal sized textures, games are always up against the limits of the graphics card memory, and system memory, and eventually you've got hard drive or DVD memory on there, but you wind up with a lot of different swapping schemes, where you'll have a little low-res version of a texture, and then high res versions that you bring in at different times, and a lot of effort goes into trying to manage this one way or the other.

So when Splash Damage was starting on, really early with Enemy Territory: QUAKE Wars, they were looking at some of these different ways to render the outdoor scenes with different blends and things like that. And one of my early suggestions to them was that they consider looking at an approach where you just use one monumentally large texture, and that turned out to be 32,000 by 32,000. And I - rather then doing it by the conventional way that you would approach something like this (i.e. - chopping up the geometry into different pieces and mapping different textures on to there and incrementally swapping them for low res versus high res versions), just let them treat one uniform geometry mesh and have this effectively unbounded texture side on there, and use a more complicated fragment program to go ahead and pick out exactly what should be on there, just as if the graphics hardware and the system really did support such a huge texture.

In the end what this winds up getting us is the ability to create a great outdoor terrain texture that has far more complex interactions than anything that you would get with any kind of conventional rendering, where you've built it up out of pieces of lots of smaller textures on there, where they do some sophisticated things with growing grass up between bump maps. And then you can go back and do hand touch ups in a lot of different places to accent around features that are coming out of the surface. And this type of thing is, I'm very sure, going to become critically importance as we go forward into kind of next generation technologies on there. We've seen this over and over as we've gone through graphical technology improvements over the years, where there will be certain key elements that you start looking at in games that look really dated because they don't have the capabilities that people are seeing in sort of the cutting edge things there. And this type of unique texturing over the coming generation of games, I think, is going to be one of those, where when people start looking back at a game that's predominantly piled and doesn't have that unique artist touched sense about all of the scenes, it's going to look very previous generation.