3D/2D Shadows

CATEGORIES: After Effects, Tutorials | Steve Holmes | October 07, 2005

Getting an object in After Effects to appear to cast a shadow on a 3D-rendered background, when in fact it’s nothing more than a 2D layer, is quite a challenge-but more than easily achievable using the incredible Displacement Map filter along with a few tricks.

The specs for this project are an NTSC D1 composition at 720×486, 29.97 frames per second, at a length of 10 seconds. We’re using an Artbeats Digital Film Library clip (www.artbeats.com) from their Digital Dimensions series (clip DD111). Please note that the Displacement Map filter only ships with the Professional Bundle of After Effects 6.5, so maybe now is a good time to upgrade?

STEP 1:

Start with a new project window open (default when you launch After Effects) and double-click that window to access the Import dialog. Locate and import the Artbeats footage item to use in your animation. Create a new NTSC D1 composition (720×486), and then drag the Digital Dimensions clip into the Timeline. Because this clip was rendered from a computer, the dimensions to the comp are the same; however, if you use an actual video clip for your background, the sizes will vary, and you’ll need to hit Option-Command-F (PC: Alt-Control-F) to stretch the clip to fit the composition.

STEP 2:

Making sure the Current Time Marker is at 0 seconds (hit Home), select the Type tool from the Tools palette, click in the center of the comp, and create your title. You can always turn on the Safe Areas to make positioning the type easier. In the Character palette, we chose Industria Solid, 125 px, Optical Kerning, 10 Tracking, then changed the Fill Color to a fairly bright yellow, and applied a black stroke of around 5 pixels. Make sure that Fill Over Stroke is selected in the small pop-out menu next to the stroke width.

STEP 3:

Choose the Selection tool and go to Effect>Perspective>Radial Shadow (I never use Drop Shadow; it’s too rigid and unrealistic). In the Effect Controls palette that appears, change the Opacity to 40% and move the Light Source to 360, 90 (which is centered just above the wording), the Projection Distance to around 14 pixels, and the Blur value to around 8 pixels. This stylizes the shadow to suit the environment. Now we need to get it bending as the background rotates-this is where the Displacement Map comes into play.

STEP 4:

We can’t apply the displacement to the shadow only so we need to separate the shadow from the logo. The only way to do that is through pre-composing (or, as I like to call it, semi-rendering). Deselect the type layer and then select it again (to avoid duplicating the shadow effect by mistake), press Command-D (PC: Control-D) to duplicate the type layer, and then go to Layer>Pre-Compose. Make sure Move All Attributes. is selected (it should be the only option), check Open New Composition, name the comp something like “Shadow Only,” and click OK.

STEP 5:

In the new shadow composition, click the Transparent Background icon at the bottom of the comp window, and you’ll see the type and the shadow it casts. Next select the type layer in the Timeline and press F3 to bring up the Effect Controls palette. Check the Shadow Only option and the type disappears, nicely isolating the shadow on a transparent backdrop. Now close that comp to return to the main one, and drag the shadow pre-comp down in the Timeline to below the text layer. We have two shadows now; one is still being cast from the text layer, which needs to go!

STEP 6:

Click the small f switch next to the text layer in the Timeline to disable its effects. Now the only shadow visible is the pre-comp. Select the pre-comp, and go to Effects>Distort>Displacement Map. You’ll see a slight shift in the shadow because it’s using its own pixel values (by default) to displace itself. In the Effect Controls palette, set the Displacement Map Layer to the third layer, DD111.mov. In both of the Use For. options, choose Luminance. Now, for the Horizontal value, key in 0, and for the Vertical value, crank it up to around 70 or so.

STEP 7:

As you can see, the shadow is very broken up. A preview of the animation (0 on the keypad) will show the shadow bending, but it’s broken up because there are too many sharp variations in the pixel colors being used to displace it-and those come from the DD111 movie layer. Let’s take control of that. Select the DD111 layer in the Timeline, and press Shift-Command-C (PC: Shift-Control-C) to activate the Pre-Compose option. In the dialog, change the name to Smooth Backdrop, check Open New Composition, and click OK.

STEP 8:

In the new pre-comp, select the DD111 layer and go to Effects>Adjust>Hue/Saturation. In the Effect Controls palette, drag the Master Saturation to -100 to make the movie completely grayscale. Then go back to Effects>Adjust and choose Levels. In the Effect Controls palette, drag the Shadows black triangle marker to the right until it hits the main part of the histogram. This darkens the shadow areas a little, giving the image a little more contrast, which will help define the displacement areas better. Finally, go back to Effects and choose Blur & Sharpen>Gaussian Blur.

STEP 9:

Change the Gaussian Blur value to around 6 pixels to soften the edges of the image. This provides a smoother transition between the main contrast areas, which will soften out the aggressive displacement we saw earlier. Let’s give it a test run. In the Timeline, click the main comp tab to switch across to it and you’ll see the shadow looks much better-but still not smooth enough. Now switch back to the backdrop comp, adjust the Blur value to around 15 pixels, switch back again, and see the difference! Much better!

STEP 10:

Lastly, we need to get the original background in-we’re currently seeing the blurred, grayscale version. Drag another DD111.mov from the Project window to the Timeline (at 0 seconds), making sure it goes above the bottom layer to become layer 3. This now covers up the blurred one (which can even have its visibility turned off) to complete the animation. A final preview or render shows a beautifully distorted drop shadow, working from a customized, softened version of the backdrop movie. Explore this technique-it really can do so many wonderful things. Enjoy!

Steve Holmes is the Creative Director of Energi Design in Sausalito, California, as well as the co-host of the Total Training for After Effects video training series, and host of others such as InDesign CS, Creative Suite 2 Workflow, and Digital Video Workflow. He lives in Sausalito, California, and can be reached at steve@clickenergi.com when he’s not out training in the mountains on his road bike.

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