Faking Reflection and Refraction

Building windows reflect the world around them and bend light as it passes through (refraction). A 3D program such as Autodesk VIZ can accurately calculate reflection and refraction of the surrounding environment using a time-consuming rendering process called raytracing.

Fortunately, you don't have to wait long in Photoshop because you can reasonably fake these optical phenomena by pasting photographic images into the glazed surfaces of the image. In this section, you'll learn techniques for making windows more realistic by varying the lighting intensity with a paint brush. We'll use liquify and warp techniques in reflected images to slightly hint at refraction that takes place in the real world.

Although reflection and refraction aren't as accurate in Photoshop as in a complete 3D model, you'll find that you can get reasonable quality in a short time. These faked techniques effectively convey the idea of glazing and still reflect a bit of a building site's context to the viewer.

I'm taking you through these steps because this is something that will most likely happen in a real project. You have spent a lot of time working on your elevation in Photoshop, only to discover that you need some additional line work from CAD. Or worse yet, the design has changed again at the last minute! You don't have to start over or worry once you see how easy it is to reimport additional image layers and integrate them into your project.

1. Before you dive in, you need to import a hidden layer from the original CAD file. Launch AutoCAD, and open the file Elevation.dwg from the companion CD.

2. On the Command line, type LAYER and press Enter to open the Layer Properties Manager dialog box. Click the lightbulb icon next to Elev-7 to turn on this layer (see Figure 6.24).

3. Click the lightbulb icons next to all the remaining layers to turn them off. A warning dialog asks you whether to keep the current layer on; click No. Click OK to close the Layer Properties Manager dialog box.

4. Press Ctrl+P to open the Plot dialog box. (Click OK if you see a warning dialog box.) Choose <Previous plot> from the Name drop-down list box in the Page Setup group. All the settings you used earlier in this chapter should appear. (If they don't, refer to the "Converting AutoCAD Drawings" section of this chapter, and use the settings given there in the Plot dialog box.) Click OK, and save the plot file as E1evation-Mode12.tif on your hard drive. Close AutoCAD without saving.

Figure 6.24

Turning on a hidden layer in AutoCAD

Figure 6.24

Turning on a hidden layer in AutoCAD

5. Launch Photoshop if it is not already running. Open the file E1evation-Mode12.tif from your hard drive or from the companion CD. Press Ctrl+A and then Ctrl+C to copy the file's entire contents to the Clipboard. Once the file is on the Clipboard, you can close it without saving.

6. If you have E1evation3.psd open from the previous exercise, you can continue here; if not, open that file in Photoshop from the companion CD before continuing.

The imported layer will contain both black and white pixels. You will use the Darken blending mode to show only the black pixels.

TIP Alternatively, you could erase the white pixels on the CAD Linework layer with the Magic Eraser.

7. Press Ctrl+V to paste the image from the Clipboard into your Elevation project. Rename Layer 1 to CAD Linework, and drag it to the top of the Layers palette if it is not already there. Change CAD Linework's blending mode to Darken.

8. Press V to select the Move tool. Drag the CAD Linework layer up until it is centered in the window openings (see Figure 6.25).

Let's create a layer set to stay organized and make new layers for each of our tasks. We'll fill the window frames with black, apply layer style effects, and mask off the window area on a new layer, all in preparation for painting.

9. Create a new layer set called Windows. Then create a new layer called Frames. (This layer will appear in the set automatically.) Zoom into 100% magnification around the window area. Select the Paint Bucket tool, and make sure that Use All Layers is checked on the Options bar. Click inside each of the three window frames to fill them with black. Apply the following layer style effects to the Frames layer:

Color Overlay Select a medium gray with HSB vales of 0,0,50.

Bevel And Emboss Select Inner Bevel Style, Smooth Technique, 100% Depth, Up Direction, 5 px Size, and 0 px Soften

Figure 6.25

Reimporting CAD data: move the CAD line work up and center it in the window openings.

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10. Create a new layer called Intensity. Select the Magic Wand tool; click the Add To Selection button on the Options bar. Click inside each of the three windows to create a selection. Convert the selection to a mask by clicking the Add Layer Mask button in the Layers palette. Click the Intensity layer thumbnail to select it.

11. Select the Brush tool in the toolbox, and build up a lighting intensity by painting in grayscale. There is really no right way to do this; feel free to make brush strokes however you see fit—the point is to create variation on the glass surface—but here is what I did:

♦ I choose a 250-pixel soft brush and used the square bracket keys to change sizes and hardness.

♦ I changed the foreground color to dark gray (HSB values of 0,0,25).

♦ I painted a few diagonal brush strokes across the windows.

♦ I changed the foreground color to light gray (HSB values of 0,0,75).

♦ I painted a few more brush strokes across the windows, obscuring all the blue areas (see Figure 6.26).

At this point, you could leave the windows as they are for an abstract look. For more realism, however, you'll paste a photograph of the sky into the window area in step 14. Before this, you will need to recall the window selection from the Intensity layer mask.

12. Select the Intensity layer mask thumbnail by clicking it in the Layers palette. Right-click this mask to open the context menu shown in Figure 6.27, and select Add Layer Mask To Selection. The marching ants appear in the window boundaries.

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