AL Preparing Drawings in CAD or BIM for Enhancement RI Communicating design ideas with plans, elevations, and section drawings is second nature to TE MA related disciplines. Many professionals subconsciously assume that everyone is aware of what is D actually an obscure set of graphic conventions sur- TE rounding measured drawings. These conventions GH are either learned in design school or integrated RI through osmosis early in one’s career.
chapter 1: P r e pa r i n g D r aw i n g s i n C A D o r B I M f o r E n h a n c e m e n t ■ 2 Photo courtesy of iStockphoto, © Vasko, Image #502782 Making Drawings Readable by Everyone Does the average man or woman on the street know what a section drawing is, let alone how to read a section tag referencing a drawing? What do dashed lines represent to someone not in the design world? How do centerlines appear, and what do thicker lines indicate? More important, who cares? For those working with desi
Preparing Drawings in CAD or BIM CAD and BIM programs are primarily vector tools. Software engineers have programmed intelligence in these programs in the form of numerous parameters that control the appearance of building components for most conceivable real-world situations.
The first time you go through this procedure, you’ll need to create a raster print driver in order to export single-pixel-width lines from AutoCAD. In addition, you’ll create a custom “paper size” (actually specified in pixels) and create a custom plot style to properly export lines as pixels. Once these drivers are set up, you can use them indefinitely to convert vector drawings into raster images.
Note: If you do not follow “clean” drafting practices in CAD, your job in Photoshop will be much harder. It is best to spend some time in CAD cleaning up legacy drawings before working on them in Photoshop. Setting Up a Printer Driver and Paper Size in AutoCAD 2. Double-click the Add-A-Plotter-Wizard (as shown in Figure 1.2). Figure 1.2 Plotter driver folder 3. On the Introduction screen, click Next to open the Begin screen. 4.
Figure 1.3 Configuring the driver to be managed locally Figure 1.4 Selecting the PNG image format 6. Click Next and Next again to accept the defaults on the Import PCP or PC2 and Ports pages. 7. Click Next again and type ImagePrinter as the Plotter Name (Figure 1.5). chapter 1: P r e pa r i n g D r aw i n g s i n C A D o r B I M f o r E n h a n c e m e n t ■ 6 Figure 1.
Note: The name ImagePrinter is used in the AutoLISP file on the accompanying DVD. Please use this name so that the LISP program functions properly later in this chapter. Next, you’ll need to get rid of all the default “paper sizes,” which for this virtual image plotter driver are actually pixel sizes. You’ll then create your own custom size that is larger than any of the presets. Continue with these steps: 8. Click Next and then click the Edit Plotter Configuration button. 9.
Figure 1.7 Specifying pixel dimensions for the custom paper size chapter 1: P r e pa r i n g D r aw i n g s i n C A D o r B I M f o r E n h a n c e m e n t ■ 8 Figure 1.8 Naming the custom paper size Note: The name ImageSize is referenced in the AutoLISP program used later in this chapter. It is important that you use this name exactly. It is now time to limit the color depth that your ImagePrinter driver uses so you can create images with black and white pixels only.
19. Finally, click the Finish button in the Add-A-Plotter Wizard to create the ImagePrinter.pc3 file on your hard drive. Creating a Plot Style Table for Images In manual drafting, architects used to press harder on the pencil to make important lines thicker. These days, plot styles control line thickness in AutoCAD. When you convert vector line work, ideally you want the lines showing up as single-pixel-width lines in the image.
Here’s how to create a custom color-dependent plot style to use in creating output with your new ImagePrinter: 1. Type STYLESMANAGER and press Enter. 2. Double-click the Add-A-Plot Style Table Wizard. 3. Read the introductory message and then click Next. 4. Make sure the Start From Scratch radio button is selected on the Begin screen and click Next (Figure 1.10). Figure 1.10 Creating a color-dependent plot style table 5.
7. Click Next again and then click the Plot Style Table Editor button. 8. Click the Form View tab if it is not already selected. 9. Drag out a selection window in the Plot Styles list box that shows the color numbers (see Figure 1.12). Keep dragging until the list automatically scrolls and all 255 colors are selected. 10. In the Properties group, click the Color drop-down and select the Black option. 11. Click the Lineweight drop-down and select 0.0000 mm (see Figure 1.13).
. Click the Save & Close button. A file called Images.ctb is automatically created in the Plot Styles folder on your hard drive. 13. Click Finish to close the Add-A-Plot Style Table Wizard and close the Plot Styles folder. Now you have configured the ImagePrinter as a raster printer driver that you can use to convert vector line work in AutoCAD to the pixels of an image that you’ll be able to manipulate with Photoshop.
■ Wo r k i n g w i t h Au t o C A D 2 0 11 D r aw i n g s Figure 1.14 Plot dialog box Figure 1.15 Selecting plotter, paper size, and plot style table Figure 1.
With the drawing stretched to the maximum size relative to the image size, 1 pixel in the plot equals 0.1924 units (which are inches in imperial units). We must rationalize this arbitrary measure to the nearest common fraction in order to maintain graphic scale in Photoshop. In other words, rationalizing in this context means changing 0.1924 units to 0.25 units. Continue with these steps: 8. Deselect the Fit To Paper check box in the Plot Scale area of the Plot dialog box. 9. Change the unit value from 0.
Make a mental note of the final equation (in this case, 4 pixels = 1 inch) or write it down. We will input this equation into the LISP program next. If you were plotting a drawing depicting something larger than my house, you would likely require a different plot scale to fit the building within the fixed grid of 3000 × 2000 pixels. Perhaps 8 pixels = 1 inch would rationalize a larger building (1⁄8″ scale).
chapter 1: P r e pa r i n g D r aw i n g s i n C A D o r B I M f o r E n h a n c e m e n t ■ 16 Figure 1.18 lay2img.lsp open for editing in AutoCAD’s Visual LISP integrated development environment 7. Switch back to AutoCAD, type lay2img, and press Enter to open the Save Image Files Of Each Layer dialog box, which prompts you to choose a path and a prefix name to save the image files of each layer. Make a subfolder called Output on your hard drive, type the prefix name Home, and click Save.
Note: If you own AutoCAD and Revit Architecture as many architects do, you’ll gain the most flexibility in Photoshop by exporting a DWG file from Revit, cleaning it up in AutoCAD, and proceeding to follow the AutoCAD instructions in the previous section. Carrying Revit’s Default Treatment of Lineweight into Photoshop Revit has built-in export functionality that supports raster image creation directly from Revit’s vector database. Perform the following steps to export an image from Revit: 1.
Figure 1.20 Exporting an image from Revit 6. Select Current Window in the Export Range area and set PNG as the format for nonshaded views (Figure 1.21). chapter 1: P r e pa r i n g D r aw i n g s i n C A D o r B I M f o r E n h a n c e m e n t ■ 18 Figure 1.
7. Click OK to create the Level2.png image file (Figure 1.22). Figure 1.22 Image created through Revit’s export feature In Revit Architecture 2011, the export image feature does not respect Revit’s Thin Lines mode. Thin Lines mode is useful if you want to forgo lineweights in Revit entirely. If you have a large monitor with a graphics card that supports a high enough resolution, you can take a screen capture to use as the basis for enhancement in Photoshop.
Thin Lines chapter 1: P r e pa r i n g D r aw i n g s i n C A D o r B I M f o r E n h a n c e m e n t ■ 20 Figure 1.23 Activating Hidden Line and Thin Lines modes 4. On the Mac, the default keyboard shortcut to save a picture of the screen as a file is Shift+Command+3. The keyboard shortcut for this feature can be changed under the Apple menu > System Preferences > Keyboard And Mouse > Keyboard shortcuts. On Windows, press the Print Screen key to copy everything on the screen to the Clipboard.
7. Choose Layer > Flatten Image And File > Save. Save the image as Level2thin.png. The final image is shown in Figure 1.24. 21 Note: Neither of the methods for exporting images from Revit preserves graphic scale. Use AutoCAD or another CAD program that enables you to map a specific number of pixels to the drawing unit (such as inches or centimeters) if you want your enhanced drawings to print to scale. ■ Wo r k i n g w i t h R e v i t A rc h i t e c t u r e 2 0 11 M o d e l s Figure 1.
