Andrew Glassner’s Notebook http://www.glassner.com Digital Weaving, Part 3 ______________________________ n my last two columns I described the theory and al clothing, kilts, and other formal wear. Because some Ipractice of weaving, and I presented a language for clans and families are protective of their registered tar- creating woven patterns. This time I’ll talk about the tans, there arose a need for some shared patterns that important and interesting fabrics known as tartans, and people could wear when they gathered as a group. For Andrew then discuss writing a program to simulate a loom. example, if a traditional marching band got together and Glassner everyone wore their own family’s sett, it could look like a A quick review crazy mishmash of patterns. To help unify groups that Recall from part 1 that a twill is a distinctive pattern don’t have their own tartan, three setts (Hunting Stewart, type, formed by a tie-up that creates a diagonal design. Caledonia, and Black Watch) have been generally accept- Perhaps the best-known twill fabric today is denim, but ed as universal tartans that may be worn by one and all. close behind that is the Scottish tartan. Tartans are the The Hunting Stewart pattern (see Figure 2) has been familiar-colored plaids that have traditionally adorned around since the early 1800s. The Caledonia sett (Figure kilts and other formal Scottish clothing. 3) probably dates back to about 1800, and members of Tartans always use the same pattern of colors in the the British Army have worn the Black Watch (or warp and the weft; weavers say that such a pattern is Government) sett (Figure 4) since the 1740s. “tromp as writ” (for complete discussions of weaving Tartan colors are generally drawn from a palette of a terms and ideas, please see the previous installments of couple of dozen colors, with custom colors occasionally my column in the November/December 2002 and included for specific setts. Most colors are referred to with January/February 2003 issues). The result is that tartans labels that consist of just a few letters. I’m not aware of are made up of intersecting stripes of different widths and any standardized RGB list of these colors, so I examined colors. As Figure 1 shows, when two stripes of different and measured several hundred tartans and compared colors overlap, we get a blended color that mixes equal their actual colors against their labels. Some variation amounts of each. When two stripes of the same color exists, of course, but the colors are pretty consistent across overlap, we get a solid rectangle of that color. The color different manufacturers and sources. Table 1 summarizes pattern that describes a particular tartan is called its sett. Today’s tartan Today weavers regularly produce thousands of differ- ent setts. Tartan cloth is used casually and for ceremoni- 1 In a twill, when two stripes of differ- ent colors over- lap, we see an equal mix of their colors. When the two stripes have the same color, we see a solid block of that color. 2 The Hunting Stewart tartan. The AWL (recall that AWL is Andrew’s Weaving Language, which I described in detail in part 2) expression for this sett is B 9 G 4 B 9 K 3 B 3 K 8 G 27 R 4 G 27 K 8 G 5 K 13 G 4 K 13 G 5 K 8 G 27 Y 4 G 27 K 8 B 3 K 3 tartan. 80 March/April 2003 Published by the IEEE Computer Society 0272-1716/03/$17.00 © 2003 IEEE Table 1. RGB values for tartan colors, identified by their traditional initials and a more informative label. Initial R G B Name A 60 132 172 Aqua B 44 58 132 Blue DB 12 10 76 Dark blue LB 124 130 196 Light blue MB 20 26 68 Dark blue NB 4 2 36 Navy blue RB 4 2 100 Royal blue C 148 2 36 Dark pink VLC 220 170 172 Pink DG 4 50 20 Dark green FG 68 106 84 Blue-green G 4 82 36 Green LG 44 154 20 Light green MG 4 58 20 Darker green 3 The Caledonia tartan. The AWL expression for this K 20 18 20 Black sett is R 42 A 18 K 4 A 4 K 4 A 18 K 36 Y 6 G 42 R 26 K 6 R 26 M 116 26 52 Magenta W 4 R 26 tartan. DN 76 74 76 Dark gray LN 188 186 188 Light gray N 124 122 124 Mid-gray DO 220 90 4 Dark orange LO 236 114 60 Light orange O 252 74 4 Orange P 116 2 116 Purple DR 204 2 4 Dark red LR 204 42 44 Light red R 204 2 4 Red WR 100 2 44 Dark magenta S 228 86 4 Sandy yellow DT 68 18 4 Dark tan LPT 204 150 100 Slightly light tan LT 148 102 52 Light tan RT 244 90 44 Reddish tan T 84 62 20 Tan MU 204 122 20 Orangeish W 228 226 228 White DY 148 122 4 Dark yellow LY 244 218 4 Light yellow Y 236 194 4 Yellow 4 The Black Watch tartan. The AWL expression for this sett is B 22 K 2 B 2 K 2 B 2 K 16 G 16 K 2 G 16 K 16 B 16 K 2 B 2 tartan. ing with the user interface. Figure 5 (next page) shows a screen shot of the digital loom in action. This figure includes a graphical editor window that I didn’t include the tartan colors. Note that white and black aren’t at the in the screen shot from part 2 of this column. I built this limits of the RGB range. This is because natural wools because I thought it might be fun to enter AWL expres- have a more limited color gamut than CRT phosphors. sions by drawing them, rather than typing them in. The main control form in Figure 5b and the woven Building a digital loom fabric output in Figure 5c were the only two windows I I built my digital loom using C#, a new programming had for quite a while. The weaving display shows the language from Microsoft. For many years I’ve been hap- warp and weft patterns and the tie-up using tradition- pily programming in good, old-fashioned, vanilla C. al black-and-white matrices, with thread colors drawn I decided to use my digital loom as an immigration pro- outside them. This is mostly a read-only display, but you ject into the C# language and its associated .NET envi- can flip bits in the tie-up by clicking on them. ronment for writing Windows code. I was surprised by The panel in Figure 5b holds most of the basic con- how easy it was to write my program in this system, and trols. The upper left of this panel has counters to set the in the course of this one project I’ve become a C# convert. width and height of the displayed fabric in the weaving Let’s look at the digital loom from the outside–in, start- window. The other major controls are buttons to speci- IEEE Computer Graphics and Applications 81 Andrew Glassner’s Notebook (b) (c) (a) 5 A screen shot of my digital loom. Figure 5a shows the color chips. Figure 5b is the main control panel, and the window in Figure 5c holds the woven fabric. Figure 5d is my graphical AWL editor, and Figure 5e is the AWL evaluation window. (d) (e) fy some details about the display itself, saving and load- tern, and copies that into the corresponding box in the ing weaving files in the weaving information file (WIF) main form. That way you can see what your expression format, and a button to save the weaving in PostScript. translates to, while the AWL is still there and editable. A The left side of this panel has two sets of four text boxes. ninth box on this form lets you enter an AWL expression Each set (one for the warp threads, one for the weft) lets for the tieup. me enter expressions for the threading pattern, thread I thought it might be fun to write a graphical editor colors, thickness, and spacing. There’s also a numerical for AWL expressions, and you can see that window in counter for identifying how many threads are to be used Figure 5d. Like most such editors, you can create and for that pattern. delete nodes, drag them around, change the wiring, Because I specify colors by name in the text fields and so on. Once you have a drawing you like, you iden- (such as black or aqua), I provided a little color selector tify which AWL expression window you want to send it panel as well, shown in the upper right. It contains all to, and push the send button to translate the drawing the default colors in the .NET environment, as well as into AWL. If you like the expression you’ve created, then all the tartan colors named in Table 1. You can also cre- you press the button below that window as usual to ate your own colors and add them to the list. If you click evaluate it and pass it to the main form. The graphical on a color chip, its name is appended to the list of colors editor is interesting to play with, but I eventually found in either the warp or weft window, depending on which that I preferred to type and edit my AWL expressions of the two radio buttons you’ve selected.