Masking and Adjusting a Displacement

Using different techniques in creating your displacement map for varying needs, you must keep in mind the scale of the source image and how much displacement you want to apply to generate motion.

In the image Reflect.jpg found on the DVD, we just want to put a slight motion in the water without affecting the shoreline (Figure 2.18). We need a denser displacement map for this project because we don't want to create a lot of violent motion in the water.

Starting with a new file, 720 x 480 pixels, Grayscale, apply the Difference Clouds filter (Filter > Render > Difference Clouds). Repeat the filter application at least a dozen times (F/Ctrl+F) until you have a detailed swirl pattern with a lot of contrast (Figure 2.19). Next, add a new layer and apply the Clouds filter to it. Adjust the opacity of the layer to 50%, and the resulting image is softened but the details still show through the surface (Figure 2.20).

Figure 2.18 This image will require a displacement map with more density for a smaller scale water surface texture, plus a mask to keep from affecting the shoreline or the trees in the background.

u Figure 2.19 Reapplying the Difference Clouds filter over itself several times creates an intricate swirl pattern.

u Figure 2.19 Reapplying the Difference Clouds filter over itself several times creates an intricate swirl pattern.

Using the new displacement map you just created and the Reflect.jpg image from the DVD, create a new project in After Effects and follow the steps in the previous project for setting up and importing. Similarly to the previous displacement map project, follow the steps to create an animated pre-composition of the displacement map layer. Use the same Offset settings for the speed of the animation loop.

Apply the displacement map effect to the reflection image, selecting the pre-composition layer as the displacement source, and use Luminance for both Horizontal and Vertical displacement. For this project, leave the default settings for pixel movement, as we need a more subtle effect applied to the image, and the scale is much lower.

Figure 2.20 A 50% Cloud layer added above the swirl pattern softens it without losing detail.

We now need to mask the upper portion of the displacement map so the effect is applied only to the water in the image. Open the displacement map composition in the Composition window. Add a solid color layer (Layer > New > Solid), and set the color to 50% gray (128 R, 128 G, 128 B). To quickly apply an adjustable mask, we'll use a fixed Linear Wipe transition (Effect > Transitions > Linear Wipe). Set the Wipe Angle to 0° and the Transition Completion to 30%. This will place the edge of the effect close to the tree line, but adding a Feather of 75 pixels will make a smooth transition into the water and scale back the amount of movement in the water near the shoreline (Figure 2.21).

Figure 2.21 Adding a solid layer and applying a static transitional wipe will mask the effect of the displacement map to the image.

Run a RAM Preview to test the animation of the displacement map effect and adjust the speed and pixel displacement as necessary.

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