Of course it's the "fence" that allows this second solution to work.
If your student didn't know about the "fence", I suppose he/she felt
an urge to use "bounce" in an attempt to contend with the situation at
the boundary, and that led to the complications we've seen.
This is probably a case where trying things out very early in the
authoring process would have been helpful. Trying out the simple
"forward" script would have revealed that it already worked, with the
only task remaining being to experiment with different values for the
scaling factor to get the best "feel," and hence the siren song of
"bounce" might have been avoided.
Cheers
-- Scott
On Feb 23, 2008, at 4:56 PM, polishookm wrote:
Scott, thanks very much for both solutions (and that great
explanation about the fence).
The solution you've proposed here is pretty much what the student
began with. Except his scaling factor was slightly higher.
I'll see if I can post the project once it's finished.
Ab,
Mark
Scott Wallace wrote:
And here's a very different, and perhaps nicer, one-line solution.
------------------------------------------------------------------------
Cheers,
-- Scott
On Feb 23, 2008, at 2:10 PM, Scott Wallace wrote:
"Bounce" is particularly unsuited to this example, because it
reverses the direction the paddle is "heading" and hence reverses
the motion brought about by "forward" commands. This makes it
hard to retain an intuitive relationship between the joystick and
the motion of the paddle.
FWIW here's a script giving good, or at least intuitive, joystick/
paddle action:
<positionPaddle.jpg>
Cheers,
-- Scott
On Feb 23, 2008, at 5:30 AM, Herbert König wrote:
Hi Mark,
p> That's an interesting observation. Did you, perchance, play
with it to
p> see what a more intuitive (for you) solution would look like?
I had the
thanks for asking, that made me try :-))
p> All suggestions welcome ...
Nearly everything i know about Etoys is from the Squeak video
DVD. So
I opened the viewer of the paddle and it has a tile "PongPaddleA's
heading" which jumps between 0 and 180 when bouncing.
So the simple solution would be to add a "PongPaddleA's heading =
0"
to the script. I thought I'd just have to drop the tile onto the
script. But this doesn't work, the script doesn't accept the tile.
This reminded me of several posts on squeak dev that 3.9 is not
good
for etoys. So I guess the Thing to do is follow Scott's advice
and use
a Squeakland image.
Dropping the Project onto a 3.8 image doesn't work, this is also
known.
So I redid it from Ground up in my 3.8 image using an arrow as the
pong paddle (guess why). It made the sound but didn't turn on
bounce.
There I learned that one has to drag a tile by the arrow to get it
into a script.
Then I tried this in 3.9 and in 3.9 the arrow also didn't turn
and the
the trick with fixing the heading of the sketch also worked.
So I proved my accusations on 3.9 unfounded, Sorry 3.9 :-))
Now drop the one who did (against better knowledge) something the
first time and let the project leader speak up.
What I did with fixing the heading of the paddle in the script
was "an
ugly hack". The price to pay is more uglyness if we ever want to
use
"Paddle turn by Joysticks leftRigt" by having to simulate
differential
geometry by "absolute geometry".
So the way to go is find out what makes the Sketch (the inspector
shows the paddle is a SketchMorph) misbehave on bounce. Maybe
there is
a reason and then you should use a wide line as your paddle.
Finally:
- Attached is my changed 3.9 Project. --> Not to the list but
private
mail
- Maybe this is off topic here, at least you might get better
advice
on the squeakland mailing list (where I'm not subscribed).
- I'd be curious and willing to comment on further development of
the
project, maybe by private mail unless somebody here also wants to
follow this.
Cheers
Herbert mailto:herbertkoenig@xxxxxxx
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--
Mark Polishook, D.M.A.
Technology Coordinator
Morehead Hall, Rm 132
Center for Academic Advising and Adult Learning
Montclair State University
Montclair, NJ 07043
(973)-655-7114
http://www.montclair.edu/AcademicAdvising/html
polishookm@xxxxxxxxxxxxxxxxxx
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