Scratch

DB88 · 2010-06-13 22:30:44

The standard coordinate system everyone learns in trig has positive x to the right, positive y up, zero degrees along the positive x axis, and angles increase positively in the counter-clockwise direction. This is based on the Right Hand Rule. With this convention, sin of an angle is y/r (where r is the magnitude of the position vector), cos is x/r, and tan is y/x. The angle system used by Scratch does not work with this system, which means you must use sin for the x component and cos for the y component. Is there a good reason for why the standard Right Hand Rule convention was not followed?

scmb1 · 2010-06-13 22:50:16

Well, I don't know the answer to your question, but I do agree that it is strange and a little hard to work with... I hope someone who knows answers this- I'm curious too.

Chrischb · 2010-06-14 03:02:08

There were suggestions about changing this earlier, and I think it got a positive response... hmm

coolstuff · 2010-06-14 06:50:43

Yes, angles are measured a little weirdly and it's quite difficult to use compared to the standard way, where I can actually visualise the angle prior to testing it out...

Paddle2See · 2010-06-14 08:50:29

It is unusual...I wish I knew why as well.

Note that zero degrees being "up" is the convention used in navigation map/compass work where true North is zero degrees and true North is usually vertically up on the map. If you think of the sprite as navigating it's own little "world" consisting of the computer screen, it is consistent with that convention.

juststickman · 2010-06-14 10:57:36

Yeah, I was wondering this too... I guess Paddle2See explains it... Sorta.

Greatdane · 2010-06-14 14:11:18

I agree with Paddle2See, and also for the sake of simplicity. It's easier to think of a "world" with little kids than it is with thinking about advanced trigonometry and Right Hand Rule. tongue

juststickman · 2010-06-14 14:17:05

Greatdane wrote:
I agree with Paddle2See, and also for the sake of simplicity. It's easier to think of a "world" with little kids than it is with thinking about advanced trigonometry and Right Hand Rule.

Yeah...

I guess the only problem is that this teaches a bad habit when learning other programming languages.

coolstuff · 2010-06-14 15:37:56

juststickman wrote:
Greatdane wrote:
I agree with Paddle2See, and also for the sake of simplicity. It's easier to think of a "world" with little kids than it is with thinking about advanced trigonometry and Right Hand Rule.
Yeah...

I guess the only problem is that this teaches a bad habit when learning other programming languages.

Not to mention the negative angles... What's with that?

DB88 · 2010-06-14 17:56:45

Paddle2See wrote:
It is unusual...I wish I knew why as well.

Note that zero degrees being "up" is the convention used in navigation map/compass work where true North is zero degrees and true North is usually vertically up on the map. If you think of the sprite as navigating it's own little "world" consisting of the computer screen, it is consistent with that convention.

I understand zero being "up", but in navigation are positive angles measured clockwise, as Scratch does, or CCW?

Scratch

archived forums

#1 2010-06-13 22:30:44

Why are angles measured in a nonstandard way?

#2 2010-06-13 22:50:16

Re: Why are angles measured in a nonstandard way?

#3 2010-06-14 03:02:08

Re: Why are angles measured in a nonstandard way?

#4 2010-06-14 06:50:43

Re: Why are angles measured in a nonstandard way?

#5 2010-06-14 08:50:29

Re: Why are angles measured in a nonstandard way?

#6 2010-06-14 10:57:36

Re: Why are angles measured in a nonstandard way?

#7 2010-06-14 14:11:18

Re: Why are angles measured in a nonstandard way?

#8 2010-06-14 14:17:05

Re: Why are angles measured in a nonstandard way?

Greatdane wrote:

#9 2010-06-14 15:37:56

Re: Why are angles measured in a nonstandard way?

juststickman wrote:

Greatdane wrote:

#10 2010-06-14 17:56:45

Re: Why are angles measured in a nonstandard way?

Paddle2See wrote:

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