2.3: Animate a sprite

Standards

• • CSTA 2-AP-12: Design and iteratively develop programs that combine control structures, including nested loops and compound conditionals.

  • CSTA 2-AP-16: Incorporate existing code, media, and libraries into original programs, and give attribution.

CSTA

Code tracing is a method in which the programmer uses paper and pencil to hand trace the execution of a code segment in order to track changes and to determine the output of the code. Code tracing leads to better code writing and is an effective tool in debugging, as the programmer can isolate a segment of code to determine if it is working correctly.

Using skills developed in lesson 3.2, students work in pairs tracing the following code segment. Code Tracing Loops

Students use videos, on student page to add special effects to an animation.

Animation is the "art of illusion": a series of still frames that looks like movement to our eyes. ( Persistence of vision).

Students read/ watch about animation techniques and tips:

• a sprite will get bigger as it moves forward in a scene. Tip1

• gradually increase a special effect, using a loop, to make it the effect grow. Tip2

• add a sound effect for atmosphere. Tip3

• add a backdrop for atmosphere. Tip4

• flip costume to opposite direction and have the sprite walk out in the opposite direction Tip5

Students are expected to use at least two animation techniques in their animations.

Animation Goals:

• decide on starting costume. ( strong start )

• decide on ending costume. ( strong ending )

• choose frame rate ( wait amount). ( how the animation will vary ( from choppy to smooth) depending on the frame rate)

• add two animation techniques. ( explore two techniques that will assist storytelling goals)

Computer science Concept Goals:

• decide on starting costume. ( reinforces RESET - initialization)

• count number of times in the loop so that it will end on the correct costume - ( reinforces paper walkthrough of code)

• realize that loops take less code and are more efficient than writing repetitive statements.

• realize that loops are a good solution if you'd like to gradually change a special effect (eg. shrink or grow), using code.

Discuss the following questions:

• 1. When does a "forever loop" end?

  2. "I made a sprite, but can not find the motion commands?" Can you troubleshoot this problem?

  3. Why is it useful to trace through code, eg. counting what costume sprite is using, for each iteration of a loop?

  4. If you have more than one sprite animation, why should you offset the timing of each sprite?