CSE 203 Closed Lab 10 Instructions
Table of Contents
1. Objectives
To learn more about sprite rotations, including other methods
available for handling them.
2. Set Up
- Two students should work together at one workstation.
- In one student's account, follow the instructions given
below in section 3, Method. Remember, trading roles (driver and
non-driver) for each new session is a very good
idea.
3. Method
- Open file LOGO_Style_Sprites_Timed_W_Snd_N_Msg.kpl from the
Week04
folder in the OSU folder.
- Find the method call "Spider.FlipVertical()" and comment that
line out. Run the program. Notice now that the up arrow key
(which causes a call to "Spider.Forward( speed )") moves the sprite
forward, but that the forward part of the sprite is the back end of the
spider! The default initial forward direction of a sprite (before
any call to TurnLeft or TurnRight) is down, that is to say, in the
positive Y direction, or the direction labeled 0 degrees. Now
stop the running program and make sure its window is closed.
- Let's put that call "Spider.FlipVertical()" back in, by
uncommenting it, so we don't get confused. Now let's change the
sprite property ForwardDirection of Spider by inserting the assignment
statement "Spider.ForwardDirection = 45" after the call to
FlipVertical(). Run the program. Notice that the up arrow
key
moves the sprite
forward, but that the forward part of the sprite is now, from the
spider's point of view, 45 degrees to the spider's left. If we
now rotate the spider 45 degrees to the spider's right, the up arrow
will now take the spider forward straight down. The behavior of
property ForwardDirection seems backwards to me, but, if we need it, we
need to deal with it the way it is! Now
stop the running program and make sure its window is closed. Feel
free to comment out the change to ForwardDirection so that the changes
you make in the next step are not so confusing.
- The ForwardDirection property affects the behavior of the
following methods: Forward, Back, MoveLeft, and MoveRight. See if
you can modify this program so that the Down key causes the spider to
crawl backward (Back), and that some other keys cause the spider to
move left and right. How about the F1 key for left, and F2 for
right?
- How did that work for you? Now change the ForwardDirection
property back to 45, or to any angle you prefer, to see what happens.
- Use Intellisense to see if you can discover other
things available for Sprite objects that might interest and/or help
you. As
you do so, keep in mind that not all things in Phrogram are as
advertised. For example, I can't seem to get SetRotationOffset to
work for me in a way that's even close to its advertisement: so far
I've just been unable to figure it out. If you have similar
problems, you can ask us directly or through Carmen, or you can visit
on the WWW phrogram.com, go to Forums, Phrogram Questions and Answers,
and ask your question there.
- If you've been wondering what colors are available for the pen
and for rectangles, open the Utilities folder in Phrogram, and open and
run ColorComparison.kpl.
- Similarly, good information about fonts available for
PrintInRectangle can be found by running StandardFonts.kpl from the
Utilities folder.
4. Proctor Help
If you have a question or get stuck,
raise your hand and one of the proctors will come by to chat.