Pal files

Introduction
This article describes the structure of the proprietery PAL palette file format that was used in Fallout 1 and Fallout 2.

Purpose of PAL files
Palette files provide a conversion table from RGB values (called "rgb" in this article) to Fallout's color index (called "colorIndex" in this article) and vice versa.

Structure

 * 33536 bytes total, devided in two parts
 * First 768 bytes: RGB values for colorIndexes 0 - 255. colorIndex >> rgb conversion table
 * colorIndex 0 serves as transparency colorIndex
 * If a FRM file contains colorIndex 0 in his data section the pixel will be displayed transparent in the Fallout 1/2 engine
 * All color components for colorIndex 0 are set to 255 in the color.pal file
 * colorIndexes 1 - 228 contain real RGB values (rgb values between 0 -> 63)
 * colorIndexes 229 - 254 contain fake values (255 for each color component) and are used for animated colors
 * The real rgb values for these special colorIndexes are hardcoded in Fallout2.exe (rgb values between 0 -> 255)
 * colorIndex 255 seems to be ununsed in Fallout .FRM files and is set to 255 for each color component.
 * Last 32768 bytes: colorIndexes for a 32 * 32 * 32 cubic matrix of rgb values. rgb >> colorIndex conversion table

colorIndex >> rgb
The first 768 bytes of a PAL palette files are simply an array of 256 R,G,B structures. For those who don't know, the RGB color triplet represents the red, green and blue component of a color. Each component uses a single byte and can only range from 0 to 63(dec) in brightness. These 768 first bytes are important if you want to convert the colorIndexes of a .FRM file into useful RGB values to display the image or manipulate it.

The first part of the palette file got this structure: colorIndex:0 (r,g,b); colorIndex:1 (r,g,b,); ...; colorIndex:255 (r,g,b,)

The Fallout engine used a special brightness modifier (called brightnessMod in this article) to create a day / night lighting system. So before the final rgb values were painted on the screen, they were multiplied with the brightness modifier: 1 -> night 2 -> morning, dawn 3 -> forenoon, afternoon 4 -> high noon

rgb >> colorIndex
All data after the first 768 bytes is the rgb >> colorIndex conversion table. We assume that this table is needed as Fallout used a special lighting system. What we can say for sure is that you'll need this second part of the palette if you want to create new .FRM images. If you create new images with image editing software it will use the standard rgb palette. If you want to save it as a .FRM file now the programme needs to find the best matching colorIndex for the each single pixel.

General information
The colorIndexes from 229 till 254 are used for animated colors in Fallout; details about it can be found in a seperate article. The Fallout developers decided to hardcode the RGB values for these animated colors in the Fallout2.exe althought there was space for them in the color.pal. They've set the RGB values for the colorIndexes 229-255 to FF(hex) / 255(dec) in the .pal file and read the real RGB values just from the Fallout2.exe. This is a rather strange decision in our opinion.

Links

 * PAL animation example programme for Win32