Texture Map File Types

I'm going to wrap up this section with some of the primary image formats you'll be using when saving your work. Each file format offers different techniques of saving image information, content, and compression. Your general file-format options are these:

The format in which you save your texture map depends on the game engine you're using. See Table 1.3 later in this chapter for a list of different engines and their respective texture specifications.

The default image format in Photoshop is PSD. When you create an image, all the components of the image such as layers, styles, channels, and paths are stored in the PSD file. Always save your original work in this format first, and then save it in another format. If you don't save your image as a PSD but need to go back to make a modification, you'll simply open a flattened image without the original layers.

This is the Windows Bitmap file, based on an 8-bit (256) color palette. Typically, you'll create an image in 24bit color mode; when you save it as a BMP file, the colors in the image are palletized to 8-bit. The original Half-Life engine uses this format. The BMP format has been updated from its original format to handle 24-bit images in addition to 8-bit.

JPG (JPEG)

This is the Joint Photographic Experts Group file format, invented primarily for optimizing file sizes for things like the World Wide Web. It offers decent quality with high compression.

ZSOFT developed this popular format as a proprietary format for its PC Paintbrush program back in the DOS days. PCX has a better compression ratio than BMP but retains the same image quality. The Unreal and Unreal Tournament engines use this format.

The Portable Network Graphics format is one of the best ways to preserve image data and have compression at the same time. I'm not sure why PNGs aren't used more often; this graphics format has lossless, high compression with the capability of storing alpha (transparency) information. This format was designed to replace the popular GIF format and be seamlessly portable between computer systems. Garage Games' Torque engine uses the PNG format.

The Targa format, developed originally for the TrueVision video board, is used often when saving animation frames in 3D programs due to the high-quality image content-to-compression ratio. TGAs also store layers and transparency channels, and they're used within the Quake engine for images requiring transparency information.

TIF (TIFF)

The Tagged Image File Format is another high-quality image format that allows for storage of layers and transparency, just as with PSD files. The downside is its compression. TIF files are high quality, but they're usually huge.

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