Integrating 3D Graphics in Flash - Flash 3D: Animation, Interactivity, and Games - page 346

Bitmap Caching
Illustrator created vector-based 3D graphics in the previous examples. Once imported
into Flash, the rendered image consisted of several graphic symbols. This works fine for
static-based imagery, but what happens if we want to animate the chess piece or 3D
text? Flash has to keep track of a lot of information to move what appears to be a sim-
ple shape. In some cases, a raster graphic may be a better choice of file format. The
creators of Flash thought of this and incorporated runtime bitmap caching.
Open 10_2_MoveChessPiece_DONE.fla in the Chapter 10 folder. The chess piece was
converted into a movie clip symbol and motioned-tweened across the Stage. When
published, it moves very slowly. This is a result of Flash updating all the vector shapes
on each frame. Let's see what effect bitmap caching has on performance.
Select the movie clip on the Stage. Go to the Properties panel and select “Use runtime
bitmap caching” (Figure 10.9). Publish the movie again. The image moves much faster
across the Stage. Flash converted the contents of the movie clip into a bitmap image.
As a result, the runtime engine doesn't have to process as much data. This works well
when animating the same image over time. If the contents of the movie clip change,
Flash regenerates the bitmap image.
Figure 10.9 Using runtime bitmap caching