Palettes

Mandala Palettes

In Mandala, a palette is the name given to a set of five colors that specify the four snake colors and the background color. There are six different palettes in Mandala. They are:

Palette Name	Background Color	Snake Colors (1-4)
Classic	White	Cyan, Magenta, Yellow, Blue
Primary	White	Red, Green, Blue, Yellow
Monochrome	White	Four shades of gray
Inverted	Black	RGB(255,128,255), RGB(0,192,64), RGB(128,0,255), RGB(192,255,0)
Oriental	Red	RGB(255,255,0), RGB(0,192,64), RGB(128,0,255), RGB(128,128,255)
Custom	User set	User set

The current palette is selected from a drop-down list control on the View|Options dialog box. The custom palette snake and background colors can be changed through a second dialog enabled by selecting a button on the main dialog box. The RGB(X,Y,Z) syntax used in the table indicates the values of the red (X), green (Y), and blue (Z) intensity components of the color. A 0 to 255 (8-bit) range is used. Black, for example, would be represented as RGB(0,0,0). White is RGB(255,255,255). Red is RGB(255,0,0).

Combining Colors

The snake colors combine as the snakes move and overlap. Consider a pixel that is set to the background color. A single snake enters the pixel. By definition, the pixel is set to the snake color, regardless of the background color. When the snake leaves the pixel, when the tail finally gets to that point, the color of the pixel will revert to the background color. The situation becomes more interesting when snakes combine with other snakes, including themselves.

At the computer logic level, snake colors are combined with the XOR (exclusive OR) operation. This operation is often used for adding a color contribution to a pixel because a second application of the same operation will restore to the pixel to the original color. Colors are stored as a set of three, 8-bit (0 - 255) values which represent the red, green, and blue intensity. Snake combination colors are computed by XORing the snake colors with the background color. This XOR is applied to each color component, red, green, and blue.

Several interesting results arise from this algorithm.

If a snake backtracks over itself (and no other snakes are at the point), the point will revert to the background color. This is because a snake walking over itself is indistinguishable from a snake tail leaving a pixel. Both use the XOR operator. When the point finally becomes the tail from the first entrance into the pixel, the pixel will again become the snake color. It will finally revert to the background color when the tail from the second entrance leaves the point. In practice, this approach creates color regions which have intricate internal detail, as opposed to being solid blobs of color.

If the background color is black, the XOR operator will produce color mixing that mimics the real world. For example, a red snake would combine with a green snake to produce a yellow pixel. If the background color is white, however, the combined pixel color for a red and green snake will be blue. This happens because the RGB value of white, RGB(255,255,255), will invert anything which is XORed with it. Blue (RGB(0,0,255)) is the inversion of yellow (RGB(255,255,0)).

Last update: Monday, July 30, 2001 03:17:33 PM
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