Previewing

Though it is common to speak of rendering as if this term only applies to final output, the processes of creating previews for the Footage, Layer, and Composition panels are also kinds of rendering.

You can preview all or part of your composition as you work, without rendering to final output. Many of the controls for previewing are in the Preview panel.

After Effects allocates RAM to play video and audio in the Timeline, Layer, or Footage panel at real-time speed. The number of frames that can be stored for real-time playback depends on the amount of RAM available and the settings in the Preview panel.

The default preview behavior is configured to produce a preview that represents a real-time playback. When you press spacebar (the default keyboard shortcut), After Effects starts a preview with audio, and caches frames until the available RAM is filled.

You can configure the Preview options to suit your working style. Controls in the Preview panel allow you to configure preview behaviors for each keyboard shortcut (Spacebar, Shift+spacebar, Numpad-0,Shift+Numpad-0, Numpad-, or Option/Alt+Numpad-) audio, looping, caching, range, and layer controls.

To configure settings for Preview, do the following:

You can stop a preview using any of the following:

• Press any of the preview keyboard shortcuts: Spacebar, Shift+spacebar, Numpad-0, Shift + Numpad-0, or Option/Alt+Numpad-0.
  
• Click the Play/Stop button in the Preview panel.
• Choose Composition > Preview > Play Current Preview.
• Press the Esc key.

The following actions also cause After Effects to stop a preview:  

• Click into the previewing viewer panel. Clicking on the tab of the viewer panel will not stop the preview.
• Adjust a property of time, such as the Work Area bar or Time Navigator bar.
• Drag the current-time indicator (CTI) or click in the time ruler, without the Option (Mac OS) or Alt (Windows) key held down. This action also changes the current time.
• Change the composition settings of a previewing composition.
• Hide the previewing viewer panel behind another panel in the workspace. For example, click a different panel in the same group or open a new viewer panel in the same group.
• Start the render queue.

The Play/Stop button in the Preview panel and Composition > Preview > Play Current Preview are linked to the shortcut currently displayed in the Preview panel. Using these actions to stop a preview has the same result as pressing the currently displayed keyboard shortcut.

The following are the default preview settings for each of the preview keyboard shortcuts:

When you preview only audio, it plays immediately at real-time speed, unless you’ve applied audio effects other than Stereo Mixer, in which case you may have to wait for audio to render before it plays.

Set the sample rate for audio for the entire project in the Project Settings dialog box (File > Project Settings).

The Audio Hardware and Audio Output Mapping preferences determine the behavior of audio previews. The output module settings determine the quality of audio in final output. In the Audio Hardware pane of the Preferences dialog box (Edit > Preferences > Audio Hardware), you can select the device class, map the default output and change the settings, and set the latency.

• To manually preview (scrub) video in the Timeline panel or go to a specific frame, drag the current-time indicator.
• To scrub audio in the Timeline panel, Ctrl+Alt-drag (Windows) or Command+Option-drag (Mac OS) the current-time indicator (CTI).
• To scrub audio and video in the Timeline panel, Ctrl-drag (Windows) or Command-drag (Mac OS) the current-time indicator (CTI).

If you stop moving the current-time indicator (CTI) with the mouse button depressed while scrubbing with audio, a short section of audio loops.

During previews, the Audio panel volume unit (VU) meter actively displays audio volume levels. At the top of the VU meter, signals indicate when the audio is clipping—a distortion that occurs when the audio signal exceeds the maximum level that the audio device allows.

To view the VU meter and levels controls in more detail, increase the height of the Audio panel.

Choose Options in the Audio panel menu to specify the following options:

• With all previewing methods—as with rendering to final output—a layer is visible in rendered previews only if its Video layer switch is selected.
• The following are some of the factors that influence the speed with which previews are rendered:
  • Layer switches
  • Fast Previews settings
  • Preference settings
  • Composition settings

Use the Resolution/Down Sample Factor settings menu which is one of the simplest and most influential of the preview settings controls. Choose a value other than Full from this menu to see all previews at a lower resolution.

• When possible, preview on the same kind of device that your audience use to view your final output. For example, you can preview on an external video monitor.
• If color management is enabled, you can preview a composition, layer, or footage item as it appears in the output color space. (See Simulate how colors will appear on a different output device.)

The most basic way of previewing frames is to manually preview by moving or dragging the current-time indicator (CTI).

The time ruler visually represents the time dimension of a composition, a layer, or a footage item. In a Layer or Footage panel, the time ruler appears near the bottom of the panel. For a Composition panel, the time ruler appears in the corresponding Timeline panel. The time rulers in different panels represent different durations. The time ruler in a Layer or Footage panel represents the duration of the contents of that panel; the time ruler in the Timeline panel represents the duration of the entire composition.

On a time ruler, the current-time indicator indicates the frame you are viewing or modifying.

• To go forward or backward one frame, click the Next Frame or Previous Frame button in the Preview panel, or press Page Down or Page Up.

• To go forward or backward ten frames, Shift-click the Next Frame or Previous Frame button, or press Shift+Page Down or Shift+Page Up.

• To go forward a specific period of time or number of frames, click the current-time display, and then enter the plus sign (+) followed by the timecode or number of frames to advance. For example, enter +20 to go forward 20 frames or 1:00 to go forward one second. Precede the value by the minus sign (-) to go backward. For example, enter +-20 to go backward 20 frames or +-1:00 to go backward one second.

• To go to the first or last frame, click the First Frame or Last Frame button in the Preview panel, or press Home or End.

• To go to the first or last frame of the work area, press Shift+Home or Shift+End.

• To go to a specific frame, click in the time ruler; click the current-time display in the Footage, Layer, Composition, or Timeline panel; or press Alt+Shift+J (Windows) or Option+Shift+J (Mac OS). You can also drag the current-time display in the Timeline panel to modify the value.

• Shift-drag the current-time indicator to snap to keyframes, markers, In and Out points, the beginning or end of the composition, or the beginning or end of the work area.

• In the Timeline panel, click the Zoom In button or the Zoom Out button , or drag the zoom slider between the buttons.
• On the main keyboard, press the = (equal sign) key to zoom in or press the – (hyphen) key to zoom out in time.
• Drag the Time Navigator Start or Time Navigator End brackets to zoom in or out on a section of the composition time ruler.

• To zoom out to show the entire composition duration, press Shift+; (semicolon) with the Composition panel or Timeline panel active. Press Shift+; again to zoom back in to the duration specified by the Time Navigator.
• To zoom out to show the entire composition duration, Shift-double-click the Time Navigator. Shift-double-click it again to zoom back in to the duration specified by the Time Navigator.
• To zoom in to show individual frames in the time ruler, double-click the Time Navigator. Double-click the Time Navigator again to zoom out to show the entire composition duration.
• To zoom in the Composition, Layer, Footage, and Timeline panels using multi-touch gestures using two fingers, pinch your fingers closer together to zoom out or move your fingers farther apart to zoom in.

For additional ways to zoom and scroll in time using the mouse scroll wheel, see Scroll or zoom with the mouse wheel.

Designating a viewer as the default panel to preview is especially useful when you have a Composition viewer that represents your final output and you always want to preview that viewer, even when you’re changing settings in other panels.

The panel that’s set to always preview appears frontmost for the duration of the preview.

• Click the Always Preview This View  button in the lower-left corner of the panel.
  
  OR

• Click the Primary Viewer  button in the lower-left corner of the panel. 
  

The Primary Viewer button is located next to the Always Preview This View button in the lower left of the Composition, Layer, and Footage viewer panels.

Primary Viewer functions similarly to Always Preview This View, except that Primary Viewer only defines which viewer or view is used for audio and external video preview.

• Only one view can be set as Primary Viewer; enabling it for a viewer or view disables it in any other viewer or view where it had previously been enabled. 
• When Primary Viewer is disabled, the most recently active viewer or view is used for audio and external video preview. 
• When you switch to a different viewer or view, that viewer or view takes control of audio and external video preview.

After Effects provides several options for previewing that make various tradeoffs between speed and fidelity.

Each preview mode provides a different balance between quality and speed for playback and for updating of images during interactions, such as when you drag a layer in the Composition panel or modifying a property value in the Timeline panel.

Draft 3D and Live Update modes apply to all views of a composition.

The Fast Previews options range from higher quality but slower performance (Off), to lower quality but higher performance (Wireframe).

• In Draft, Fast Draft, and Wireframe modes, the Current Renderer menu button's lightning bolt appears orange. In Adaptive Resolution, it appears orange when the composition is downsampled. In these modes, the name of the mode appears in the upper-right corner of the Composition view.
• If adjusting a property or scrubbing through the Timeline takes a long time in Final Quality mode, Adaptive Resolution, or Draft modes, the scene temporarily switches to show wireframes. The frame finishes rendering when you stop moving the mouse.
  
• If you are in a ray-traced 3D composition in Draft mode, and then switch to it to a Classic 3D composition, the fast preview mode automatically switches to Adaptive Resolution.
• If you want to update more than one active view when scrubbing while holding down the Ctrl (Windows) or Command (Mac OS) key, enable the "Share View Options" option in the Select View Layout pop-up menu.
• Click the Current Renderer menu button in the upper-right corner of the Composition panel to quickly open the current renderer settings in the Composition Settings dialog box. This method is applicable to a 3D layer, camera, or light in the composition.

In the Previews preferences category, you can choose the quality and speed of color management and zoom operations used in previews.

From the Zoom Quality or Color Management Quality menu, choose one of the following:

• Faster
• More Accurate Except Cached Preview
  
• More Accurate
  

The Zoom Quality preference affects the quality of scaling performed for pixel aspect ratio correction in the Composition and Layer panels.

The region of interest (ROI) is the area of the composition, layer, or footage item that is rendered for previews. Create a smaller region of interest to use less processing power and memory when previewing, thereby improving interaction speed and increasing preview duration.

By default, changing the region of interest does not affect file output. You can change the size of your composition and select what portion is rendered by cropping to the region of interest.

• To draw a region of interest, click the Region Of Interest button at the bottom of the Composition, Layer, or Footage panel, and then drag to select a viewable area of the panel.

• To switch between using the region of interest and using the full composition, layer, or footage frame, click the Region Of Interest button.
• To move or resize the region of interest, drag its edges or handles. Shift-drag a corner handle to resize while preserving aspect ratio.
• To crop the composition to the region of interest, choose Composition > Crop Comp To Region Of Interest.
• To crop the output to the region of interest, choose Use Region Of Interest in the Crop section of the Output Module Settings dialog box. (See Output module settings.)

The work area is the part of the duration of a composition that is rendered for previews or final output. In the Timeline panel, the work area appears in a lighter shade of gray.

• To set the work area start time or end time to the current time, press B (begin) or N (end), respectively.
• To set the work area, move the start and end work area markers in the time ruler.

• To move the work area, drag the center of the work area bar left or right.
  

• To expand the work area to the size of the composition, double-click the center of the work area bar.

• To show the duration of the work and the times of its beginning and end in the Info panel, click the work area bar.

When you want to compare one view to another in a Composition, Layer, or Footage panel, take a snapshot. For example, you may want to compare two frames at different times in a movie.

Snapshots taken in one kind of panel can be displayed in another kind. For example, you can take a snapshot of a Layer panel and display the snapshot in a Composition or Footage panel. Displaying a snapshot does not replace the content of the panel. If the snapshot has a different size or aspect ratio than the panel in which you display it, the snapshot is resized to fit the current view.

Snapshots are for reference only and do not become part of the layer, composition, or rendered movie.

A sound is generated when you take a snapshot.

• To take a snapshot, click the Take Snapshot button at the bottom of the panel or press Shift+F5, Shift+F6, Shift+F7, or Shift+F8.
• To view the most recent snapshot taken with the Take Snapshot button or Shift+F5, click and hold the Show Snapshot button at the bottom of the panel.
• To view a specific snapshot, press and hold F5, F6, F7, or F8.
• To purge a snapshot, hold down Ctrl+Shift (Windows) or Command+Shift (Mac OS) and press F5, F6, F7, or F8.
• To free all memory used to store snapshots, choose Edit > Purge > Snapshot.

You can preview the contents of your Layer, Footage, or Composition panel on an external video monitor. Previewing on a video monitor requires additional hardware, such as a video capture card or a FireWire port.

Previews can be displayed on a second monitor connected to your video display card, such as via DVI, DisplayPort, or HDMI. If you are using a video capture card to connect an external video monitor, install the appropriate drivers and connect the monitor to view previews. If you are using a FireWire port, first connect a digital camcorder or similar device to the port; then connect the video monitor to the device. For more information on setting up FireWire previews, see the documentation for your digital camcorder, VCR, or other devices.

The video preview sent to an external monitor using Mercury Transmit is color-managed (treating the external video preview monitor as an HDTV Rec. 709 device). For more information, see the Video preview using Mercury Transmit article.