Twelve and Twenty-four Color Mode
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The Viewer offers the option of displaying depth, surveys, and sections using either 12 or 24 colors. To change the number of colors, select "Options|24 Color Mode" from the menu bar. The 12/24 color modes also apply to the "Color By Depth" and "Color By Date" options in the Complex Plotting Feature.
Twelve Color Mode. The Viewer normally uses a rainbow-colored pattern of 12 colors to display things like depth, surveys, dates etc. These colors were chosen because they are available in the basic VGA palette of colors. This means that these colors can be used with virtually any video card or in any video mode. However, these colors have several shortcomings. First of all, they are not evenly spaced. Second, the small number of colors means that subtle feature in caves may be invisible.
Twenty-four Color Mode. Because of the limitations of 12-color mode, the Viewer also has the option of using a rainbow palette of 24 colors. These colors are evenly spaced, but they cannot be displayed in any video mode. They require that your video card be set to a video mode that has more than 256 colors. If you are running in a video mode that displays 256 or less, some of the colors will be lost. Most modern video cards support more than 256 colors with no speed penalties. Video cards have several different ways specifying the video mode. Here is a chart of common video modes and the number of colors:
Setting Color Modes. To set the video mode on your computer, go to "My Computer" and then select the "Control Panel" icon. Next, select the "Display" icon and choose the "Setting" tab. Select the number of colors from the "Colors" section. Also, some video cards have special tools that stay in the "System Tray" and allow you to quickly change video modes.
VGA Palettes. One option for dealing with a large number colors in 256-color mode is to maintain specialized color palettes. I have chosen not to do this because it would require at least four different palettes and would interfere with the colors in the bitmap backgrounds. Also, most modern video cards support more than 256 colors without any speed penalties. (If anyone has a pressing need for palette support, let me know.) For more information, see the discussion on dithered colors.