Page 70 - Learn To Program With Scratch

the Looks Palette
You can draw images directly on the Stage using the pen commands, but
costumes provide another powerful, and sometimes much easier, way to
add graphics to your programs. The commands in the Looks palette will let
you manipulate costumes to create animations, add thought bubbles, apply
graphic effects, and change a sprite’s visibility. We’ll explore those com-
mand blocks in this section.

Changing Costumes to Animate
Animation .sb2 You know how to send a sprite from one point to another on the Stage, but
static sprites don’t look very lifelike as they jump around. If you use differ-
ent costumes and switch between them fast enough, you can make a sprite
appear as if it were really moving! Open the file Animation.sb2 to try out the
animation in Figure 3-1.

This application contains one sprite
with these seven costumes.

Figure 3-1: You can create the illusion of animation by
switching among different costumes .

This application contains one sprite with seven costumes along with
one script. You can see the seven costumes in the Costumes tab and the script
in the Scripts tab of the sprite. When you run the application by clicking the
green flag, the stick figure will appear to walk on the Stage. The key to its
motion is the next costume command, which tells the sprite to put on the
next costume in its list. If the sprite is wearing the last costume in the list,
it will roll over to its first costume.
When the green flag is clicked, the script starts a forever loop with a
wait block at the end to create a delay of 0.1 seconds after each costume
change. If you remove this delay from the script, the stick figure will appear
to run instead of walk. Experiment with different values for the move and
the wait blocks and see how they affect the animation.
Although you could draw this walking stick figure with the pen
commands, you would need to write a long script. On the other hand,
once you draw these costumes, programming the animation is a breeze.
Remember that you can create images using your favorite paint program
or with Scratch’s Paint Editor.

48 Chapter 3
www.it-ebooks.info