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Lesson 2. Ballet Special Bumper >  Using Motion Sketch to create a motion path

Using Motion Sketch to create a motion path

The Motion Sketch plug-in is a feature within After Effects that allows you to create fluid motion paths by drawing. Rather than setting individual position keyframes, you will draw your own freehand motion path using Motion Sketch. As you draw a motion path with the mouse or pen, Motion Sketch records and sets keyframes for the position of the layer as well as the speed at which you draw. This path can be drawn anywhere within the composition window or even on the pasteboard. If you speed up, slow down, pause, and start again as you draw a path, this motion will be recorded in the keyframes that are created.

While you sketch a path with Motion Sketch, After Effects plays the audio files in the composition. (The Audio button in the Time Controls palette must be clicked to enable audio playback.) This feature is useful if you want to create a motion path that will match cues in the audio.

Here you'll use Motion Sketch to animate a snowflake that flutters in the background to the music as the type animates and dances off the screen.

Preparing the snowflake layer

Before you create the motion path, you'll import the snowflake layer, set up the work area, and then set some transform values for the layer.

  1. Choose File > Import > Footage Files.

  2. Select the file Snow.ai from the 02Lesson folder, and then click Open.


Note: When you import an Adobe Illustrator file as a file instead of as a composition, After Effects adds Merged/ to the filename to indicate that layers in the file have been combined, or merged.

  1. Select the file Audio.mov, click Open, and then click Done.

  2. Set the current-time marker to 00:00.

  3. Drag Audio.mov from the Project window into the Time Layout window.

  4. Resize the Composition window so you can see more of the pasteboard area around the frame. This lets you create a motion path that extends outside the composition frame.

    Because you want to position the snowflake, you'll drag it into the Composition window instead of dragging it into the Time Layout window, which would center it. Regardless of whether you drag an item into the Composition window or the Time Layout window, the item appears in both windows.

  5. Drag Merged/Snow.ai from the Project window into the Composition Window, placing it wherever you want it to begin. For the final movie the snowflake was placed on the pasteboard (the gray area just outside of the composition frame) to flutter in from off screen.

    Figure .

  6. In the Time Layout window, display the Scale, Rotation, Opacity, and Position properties for the snowflake layer. You can use keyboard shortcuts to display just these properties: press the S key, Shift+R, Shift+T, and Shift+P.

    Figure .

    Next, you'll set scale and opacity values for the entire Merged/Snow.ai layer. Because these values won't change over time, you don't need to set keyframes for them.

  7. Set the scale value to 75%, and set the opacity to 80%, but do not set keyframes. Then set an initial Rotation keyframe at 00:00 with a value of 0.

  8. Go to 7:00 and change the rotation value to 1 revolution. This will create one slow revolution over the 7 seconds during which the snowflake is on-screen.

  9. Click the Quality switch icon for the snowflake layer to select Best quality, indicated by a forward solid slash.

  10. Turn on motion blur for the snowflake layer by selecting the layer's Motion Blur switch.

    Figure .

    Motion blur enhances motion that you have applied to an object. In addition to turning it on for the snowflake layer, you need to enable motion blur so it is used in previewing and rendering. Motion blur can slow down previewing and rendering, but if you don't need to see it while you work, you can speed up processing by disabling motion blur. In this case, you'll enable motion blur.

  11. Click the Enable Motion Blur button at the top of the Time Layout window.

    Figure .

  12. If the snowflake is not the top layer in the layer stack, drag it to the top position in the Time Layout window.

  13. Click Switches/Modes at the bottom of the Switches panel to display the Transfer Modes panel, and then Choose Soft Light from the appropriate menu in the mode column. Click Switches/Modes again to display the Switches panel.

    Figure .

    Soft Light is a transfer mode that will let various elements in the background footage and type elements show through the snowflake as it flutters over them. Transfer modes are applied to a top layer so that the color and luminance values of its pixels are affected by the pixel values of the layer(s) below it. This allows the snowflake to blend better as it interacts with the footage behind it. For more information and practice with transfer modes, see Lesson 4, "Multimedia Animation," or the After Effects User Guide.

    The last step before creating the motion path is to define the start and end points for the animation. This is the time frame in which the new keyframes will be set. Motion Sketch will stop automatically when it reaches the end of the work area.

  14. Set the work area to begin at 00:00 and to end at 7:00.

  15. Select the snowflake layer in either the Time Layout or Composition window.

Creating the snowflake motion path

Now that you've set up the work area and modified the snowflake layer, you are ready to create the motion path using the Motion Sketch plug-in.

  1. Choose Window > Plug-in Palettes > Motion Sketch to open the Motion Sketch palette.

  2. Leave the Capture Speed set to 100%. The motion you draw will be captured at real-time.

    Increasing this number increases the playback speed in relation to the drawing speed, giving you more time to draw the path. Decreasing this number will slow down the playback speed by the percentage you choose.

  3. Leave the Show Wireframe option selected to see the outline of the layer as you draw the motion path.

  4. Leave Keep Background deselected. If selected, this lets you view the background layers as you sketch.

    Read through the next couple of steps before clicking Start Capture so you'll better understand how Motion Sketch records your movement.

  5. Click Start Capture.

    As soon as you click the mouse, After Effects begins recording its movement, setting new position keyframes for the selected snowflake layer based upon what you draw.

  6. Position the pointer where you'd like to begin the motion path, and click and hold the mouse button and drag to draw the path for the snowflake.

    After Effects stops recording when you release the mouse button or go beyond the end of the work area.

    Figure .

  7. Expand the outline to display the Position property for the snowflake layer.

    Notice all the new keyframes. They are very close together because there is one on each frame. To view them individually, use the zoom slider to zoom into the timeline.

    Figure .

    Now you'll preview the motion created using a Wireframe preview. If your system has sufficient RAM installed, you can use RAM Preview instead. See "RAM Preview" .

  8. Ensure that the snowflake layer is still selected.

  9. Choose Composition > Preview > Wireframe or press Alt+0 (Windows) or Option+0 (Mac OS) on the numeric keypad.

  10. To revise the motion path created, delete all of the keyframes by clicking Position for the snowflake layer, press delete, and repeat steps 5 through 6 and preview again.

Smoothing motion

Because After Effects is creating a new keyframe for each frame as you draw using Motion Sketch, the resulting motion is often somewhat jerky. To create smoother motion you can apply The Smoother. The Smoother removes some of the keyframes based on a tolerance level that you choose, resulting in much more fluid motion.

  1. In the Time Layout window, click Position in the snowflake layer to select all of the position keyframes.

  2. Choose Window > Plug-in Palettes > The Smoother to open The Smoother control palette.

  3. For Apply To, choose Spatial Path.

  4. Set the Smoother tolerance to 10, and click Apply. Notice that in both the Composition window and the Time Layout window a number of keyframes are removed, and the direction handles in the Composition window are set to create smooth curves along the motion path.

  5. Preview the new motion using a Wireframe preview or RAM Preview.

  6. If you are not satisfied with the way The Smoother altered the motion path, choose Edit>Undo to undo the smoothing. Select the keyframes again and choose a different tolerance value.

  7. Save the project.

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