1. Colour in CAD Drafting Presented By: Noha Abbassy By: Ralph Grabawski Web Address: http://www.architectureweek.com/2001/0822/tools_1-1.html Topic Number:149 Date: 22 August 2001

2. Introduction All current CAD packages give you the freedom to use many colors in a drawing. Whereas CAD systems of yesteryear limited you to 255 or even just fifteen colors, today's CAD systems support the 16.7 million colors. That leaves new CAD users in a quandary: What color coding system? Why use colors at all? Consumer-oriented CAD systems, such as FloorPlan 3D, preassign colors and textures to predrawn objects. Other CAD systems use color numbers to assign textures to surfaces. FloorPlan 3D

3. The Case for Color CAD programs use color for two purposes: (1) operator cues, and (2) controlling the plotter. When a drawing contains colored elements, the colors provide cues to the operator, making him or her more efficient. It's easier to pick out a blue water pipe from a sea of red structural members than when pipes and steel beams are both drawn in black.

4. The Case for Monochrome One structural engineering firm did just that. When it came time to upgrade their CAD hardware, the firm's principals got the CAD operators involved. Since the operators are the ones who use the equipment, it made sense to let them have a say in the selection of the graphics display. The operators decided on a very high-resolution monochrome display system for two reasons: (1) the final output would always be monochrome, and (2) they would be more productive since the extra-high resolution meant less time-consuming zooms and pans. The money saved on losing color allowed the firm to spend that money on higher resolution and bigger screens.

5. Color Numbering Systems — What They Mean RGB: Red-green-blue is the system used by Windows. Each of the three primary colors ranges in intensity from 0 (black) to 255 (full color). HSL: Hue-saturation-luminance is an alternative color specification system. Hue starts with red (0) and goes through yellow (43), green (85), blue (170), and back to red (255). Saturation ranges from 0 (gray) to 255 (full color). Luminance, or brightness, ranges from black (0) to white (255). CYMK: A color system of cyan, yellow, magenta, and black, used by color printers.

6. How CAD Works with Colors CAD software doesn't work with color names but with color numbers. The software matches the number to a color. (Sometimes, the CAD software lets you specify a color name as a pseudonym for the number.) Assigning colors to layers via an AutoCAD dialog box.

7. Where to Assign Colors In general, there are two ways you can assign colors in a CAD drawing: (1) by layer; and (2) by object. The correct method is to assign color by layer. The reasoning is that you usually draft common elements on a single layer, which logically have the same color. In addition, when you change the color of a layer, the CAD system then automatically changes the color of all objects on that layer.

8. Why use colour at all? More accuracy & efficiency Less time consumption Categorization of similar elements Less monotony