Chapter 3. Structuring Movies and Laying Out Content

After elements are in Flash, whether drawn or imported, graphics or sound, bitmap or video, you must specify where they should go, when they should appear, and when they should disappear.

Like the canvas of an image editor, or the page of a page layout program, Flash has the stage. By default, the Flash stage is 550 pixels wide by 400 pixels in height, with a white background and pixels as the default unit of measurement. But you can modify any of these settings to meet your needs.

To facilitate document layout and element positioning, Flash has rulers, a customizable grid, and guides. Rulers run along the horizontal and vertical edges of the page, enabling you to see exactly where a given coordinate appears relative to the stage. The grid, like the lines on graph paper, is a regular rectangular pattern that facilitates the creation of proportionate elements. Guides are horizontal or vertical lines that you can add to a document in custom locations to be used for alignment and layout purposes: they do not appear in the output file.

Another useful layout tool is Flash's Align panel, which you can use to align various elements to each other and/or the stage. In addition, the Align panel enables you to distribute multiple elements so they are spaced out evenly.

Flash also provides controls on the stacking order of elements. That is, if two or more elements overlap, you can control which appears on top of the other. In general, more recently added elements are automatically stacked on top of older elements. If you draw a circle, and then add a line of text in the same place, the text will block the original circle where the two overlap. As discussed in Chapter 1, Flash's unique drawing system is an exceptionnewer shapes and lines can crop and blend with older shapes when they overlap.

Flash offers a more powerful system of control over stacking order than this automatic stacking, however, called layers. Layers enable you to separate elements onto discrete planes; even when drawn elements on two layers overlap, they never crop or blend.

To those familiar with traditional graphics applications, such as image editors and page layout programs, all the features mentioned so far are familiar. But Flash also enables you to specify where elements are positioned in the fourth dimension: time. That is, when you are creating animations or interactivity, you must specify when elements appear or disappear, when changes occur, and how the stage should look after these changes take place.

The primary interface element used to control stage elements as they change over time is the timeline. The timeline contains frames, which may contain content. When a frame has content, this content is displayed (if graphic), played (if audio), and so on during playback in the Flash Player. If a frame lacks content, then it is empty, and nothing is played or displayed in the Flash Player. Every movie has at least one layer and one frame, but you can add as many frames as you needup to 16,000. Each layer has its own frames, which means that one layer can have static content, while another layer has animated content, and a third layer may not have any content in a given moment at all.

Working with multimedia can be overwhelming at first, because you have to consider the composition on the stage, the vertical and/or logical organization in layers, the position and changes over time, and the architectural implications of symbols and the library. The key is to work with a movie's elements one at a time, rather than all at once. You should always try to isolate elements from each other, which you can accomplish by using layers, the timeline, and the library correctly. Once isolated from each other, it is easy to determine when and where elements should appear, how they should animate, and so forth.