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The blocks placed to make up the structures and constraints are called brushes. Although brushes can be made into various shapes and sizes, they must be solid in form. This means that they must have at least four sides, like a three-sided pyramid with a floor.
With at least four sides, they can be defined as solid, structural blocks in the game, which is important. The game performs some optimization techniques to help it to run smoothly. Part of this optimization depends on the ability of the game to define what the player can and cannot see. Because the game assumes that the player cannot see through solid brushes, this helps with that optimization.
Another restriction that brushes have is that they must be convex in shape. This means that you can’t have a single brush with a concave or U-like shape. This limitation reduces the work required by your processor during game play and, because you can place multiple brushes together to create any shape imaginable, it is a fair compromise to make.
Within each map, you must create specific boundaries with the placement of brushes. When creating buildings and other things in your map, you are confined to a single space. You have a large area in which to build; it’s kind of like building in outer space. However, if your computer had to calculate a virtual world that went on without boundaries, it would quickly run out of free memory and processing power and crash.
To avoid crashing the game, you must set the boundaries of your map. By creating a large, sealed room around all your other structures and elements, you can define these boundaries. Then, when the game begins putting your 3D world together, it won’t lose its cool and crash on you. This game-creation process is known as rendering. Rendering is the process of making your data visible on the computer screen. Your computer takes the code that has been written to the map file and turns it into visual data that makes up your game.
26 Part I: The ABCs of Modding_________________
Seeing in three dimensions
Earlier, I refer to the environment as a 3D world. What I mean by this is that, just like the world we live in, the game world also as three dimensions called the X, Y, and Z planes. One dimension runs from left to right and, in Quake 4, this is called the X plane. Another plane, the Y plane, runs from back to front. Last, the plane that runs from bottom to top is the Z plane. Together, they make up the three planes of the 3D environment. Figure 3-1 helps to illustrate these three planes.
Those of you with a background in mathematics or modeling might be confused by this configuration of axes. You would be more familiar with a vertical Y axis and a horizontal Z axis. However, in the world of gaming, these axes are reversed. This is because many games such as Quake 4 use the Cartesian coordinate system, which defines the third axis, the height, as the Z axis.
Chapter 3: Breaking Down the Game
If you were to measure a box, like the post office does before shipping, you would have to measure in these three dimensions. The width, length, and height of the box would relate to the X, Y, and Z planes respectively.
Measuring in units
The game world has its own way to express distance. Instead of using inches or centimeters, it uses units. Although it isn’t easy to picture how big a unit is in reference to real-world objects, it does relate to another digital medium of measurement: pixels. One unit in the game is equal to one pixel. This might be confusing at first, but after a week of being submersed in the mapping world, it will become second nature to you.
Measuring things this way makes it easy to create images for use within the game, but not everyone likes it. A large number of modders would rather this measurement relate directly to real-life measurements so they can more easily reproduce in the virtual world real-life environments such as their homes or offices. If you are one of these modders, the real-life conversion of units to inches is listed in Chapter 20. There you can also find other helpful measurements for reference when building your maps.
Toying with Textures
The virtual world of games is full of images. I don’t just mean the images invoked in your mind of the wonderful things you can do. Everything that you see in the game starts as unpainted objects. The walls begin as just plain boxes, and the players start out lacking in color, definition, and everything else that makes them look like players.
Painting the Walls
When the game is being built, the person doing the building puts the color into the game. This is done by placing images on everything, but these are not the same kind of images you can get with your camera. These images have additional features specified within them. These features define how light will bounce off of the image, how the image can convey the appearance of little bumps or scratches and other similar things. Altogether, these images and features make up what is referred to as a texture.