Getting started

About masks

A mask in Adobe After Effects is a path, or outline, that is used to modify layer effects and properties. The most common use of masks is to modify a layer’s alpha channel. A mask consists of segments and vertices: Segments are the lines or curves that connect vertices. Vertices define where each segment of a path starts and ends.

A mask can be either an open or a closed path. An open path has a beginning point that is not the same as its end point; for example, a straight line is an open path. A closed path is continuous and has no beginning or end, such as a circle. Closed-path masks can create transparent areas for a layer. Open paths cannot create transparent areas for a layer, but are useful as parameters for an effect. For example, you can use an effect to generate a running light around a mask.

A mask belongs to a specific layer. Each layer can contain multiple masks. You can draw masks in common geometric shapes—including polygons, ellipses, and stars—with the shape tools, or you can use the Pen tool to draw an arbitrary path.

In this lesson, you will create a mask for the screen of a desktop computer and replace the screen’s original content with a TV news promo. Then you’ll adjust the positioning of the new footage so that it fits the perspective of the shot. Finally, you’ll polish the scene by adding a reflection, creating a vignette effect, and adjusting the color.

Begin by previewing the movie and setting up the project.

1 Make sure the following files are in the AECS5_CIB/Lessons/Lesson07 folder on your hard disk, or copy them from the Adobe After Effects CS5 Classroom in a Book DVD now:

􀁴 In the Assets folder: news_promo.mov, office_mask.mov

􀁴 In the Sample_Movie folder: Lesson07.mov

2 Open and play the Lesson07.mov sample movie to see what you will create in this lesson. When you are done, quit QuickTime Player. You may delete the sample movie from your hard disk if you have limited storage space.

When you begin the lesson, restore the default application settings for After Effects. See “Restoring default preferences” on page 3.

3 Press Ctrl+Alt+Shift (Windows) or Command+Option+Shift (Mac OS) while starting After Effects CS5 to restore default preferences settings. When asked whether you want to delete your preferences file, click OK. Click Close to close the Welcome screen.

After Effects opens to display a new, untitled project.

4 Choose File > Save As, and navigate to the AECS5_CIB/Lessons/Lesson07/ Finished_Project folder.

5 Name the project Lesson07_Finished.aep, and then click Save.

Дата добавления: 2014-11-20