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Pete
Bauer on Photoshop Textures and the Lighting Effects filter can make an image jump right off the page or screen. Using a texture to create 3D, however, is a scary thing for most Photoshop users. We'll take some of the mystery out of the process. Before we get into the nuts and bolts of this week's column, I'd like to take a moment to congratulate Adobe Systems, Inc. on the successful release of Photoshop 6. The product has started arriving and is being put into production. And, judging from the nature of the requests for assistance I've received, the transition is going smoothly for most. (The problems that have arisen are, almost exclusively, user inexperience or hardware issues.) I'd also like to congratulate Adobe for its support of The Hunger Site (www.thehungersite.com), a worthwhile, United Nations-affiliated project that supplies food to hungry people around the world. The Hunger Site is just one of the causes that receives support from Adobe -- check out www.adobe.com/aboutadobe/philanthropy/main.html to learn more. I jokingly
pointed out to a colleague recently that Photoshop has a specific
learning pattern for most users: Textures are grayscale images that can be used by certain features in Photoshop to represent 3D (among other functions). The primary employer of Textures as 3D in this manner is Lighting Effects (Filter> Render> Lighting Effects...). This filter uses variations in color to represent variations in "elevation" of an image. We'll use the analogy of elevation, such as that in a relief map, throughout this discussion. Think
of land, in reality and as represented on a map, as consisting of
points above ground level (hills and mountains, primarily) and points
below ground level (valleys, bottoms of lakes and oceans, riverbeds).
If we think globally, we can think of "sea level" as the average,
with mountains being higher and oceans being lower. This leads to
the key relationship among grayscale colors in a texture: Figure 1 shows a texture image set up to demonstrate how this works. The background is neutral gray, with an RGB value of 128/128/128. The triangles and their labels were also colored using RGB values. Each of the three component colors was set to the value shown to create the appropriate shade of gray. For example, the triangle labeled 170 has a color value of R-170/G-170/B-170. Using the grayscale slider in the Color Palette, this is equivalent to 40%. (Note that 50% gray using the slider has an RGB value of 147/147/147.) The triangles on the right are white and black, with respective values of 255/255/255 and 0/0/0. The gradated image has a standard black-to-white gradient.
To the far left are the first triangles in the series. On top is a triangle (and label) filled with a gray value of 130. This is difficult to see because the background is 128 gray. The 2-point variation is virtually imperceptible. Below is a barely-visible triangle and label with values of 125. The 3-point difference can be picked up by the human eye. To
prepare this image for use as a texture, it must first be flattened
and saved as a grayscale psd file. Images in other color modes cannot
be used. To use a texture with the Lighting Effects filter, it must
appear in the target image as an Alpha channel (a mask).
Dragging the Gray channel. After the channel is dropped, it become active and visible. Click on the RGB channel to make the composite visible and de-activate the Alpha channel. The target image in this case consists of an RGB image filled with red (255/0/0). We'll use the simple red fill to show the changes in "elevation." Figure 5 shows the settings that were used. Note that the channel Alpha 1 must be loaded in the lower part of the dialog box. Figure 6 shows the result.
Observe how the shadow and highlight effects on the pairs up and down triangles are of virtually the same magnitude, and are reversed. With the settings shown in Figure 5, the left-most triangles and labels are now visible. However, there are virtually no differences among the effect at the more extreme "elevations." Looking at the gradated shape, you can see that past about the halfway mark in each direction the effect becomes uniform. To see more clearly how changes in gray values can produce different "elevations," the filter was undone and re-applied. The only change that was made was a reduction in the Flat/Mountainous slider from 76 to 2. (The slider can be seen at the bottom of Figure 5.) Textures in the form of images can also be applied using Filter> Texture> Texturizer. The dialog box is shown in Figure 8, and the result in Figure 9. Texturizer doesn't require that the texture map be an Alpha channel within the image. Rather, the Load Texture button allows you access to any .psd image. Results are far more predictable with grayscale, but color images can also be used as textures with the Texturizer. Part 2 of this two-part series will look at using textures and the Lighting Effects filter with photographic images. SIX
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