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#1 2011-03-14 04:16:34
- s_federici
- Scratcher
- Registered: 2007-12-18
- Posts: 500+
Point in Direction 0
Does someone know why in Scratch direction 0 is UP whereas in all geometry books I know direction 0 is RIGHT? Is there some other reason I'm not taking into account? This is weird as, having Scratch a cartesian system, if you calculate the direction of a straight line, direction 0 should be LEFT/RIGHT (not UP/DOWN).
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#2 2011-03-14 09:01:09
- scimonster
- Community Moderator
- Registered: 2010-06-13
- Posts: 1000+
Re: Point in Direction 0
True. There is a diagram here.
I think this should go in AAS though.
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#3 2011-03-14 09:22:58
- Paddle2See
- Scratch Team
- Registered: 2007-10-27
- Posts: 1000+
Re: Point in Direction 0
Yes, it certainly does make it interesting to try and apply standard Cartesian trig equations!
However, I kind of like it. It is consistent with the coordinate system used in navigation. Zero degrees is North, which on most maps and charts, is "up". I suspect it was done that way in Scratch because it seemed more natural - and at the time there were no trig functions in Scratch!
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#4 2011-03-14 10:39:24
Re: Point in Direction 0
That is intresting, but when you think about it, it's for a simple straight line. It could be used in Scratch if y = 1 always. 
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#5 2011-03-14 12:40:09
- TheSuccessor
- Scratcher
- Registered: 2010-04-23
- Posts: 1000+
Re: Point in Direction 0
It's easier for younger Scratchers to understand, as it's a more natural way of doing it. Also, if we used the mathematical convention that you number angles going anticlockwise, imagine how confused people could get. Still, at least it has (0,0) in the middle, with the normal coordinate system being used, which is more than most computerised things (including Squeak!) can say, having (0,0) at the top left and the value of y increasing the further down you go!
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#6 2011-03-14 13:44:11
Re: Point in Direction 0
TheSuccessor wrote:
It's easier for younger Scratchers to understand, as it's a more natural way of doing it. Also, if we used the mathematical convention that you number angles going anticlockwise, imagine how confused people could get. Still, at least it has (0,0) in the middle, with the normal coordinate system being used, which is more than most computerised things (including Squeak!) can say, having (0,0) at the top left and the value of y increasing the further down you go!
Even having (0,0) at center screen is sometimes not helpful for graphs it might be great, but for programming it's a pain as you have to take -ves into account. Problem is, Scratch uses a hybrid of programming standards and graph standards. We should somehow have an option in some remote menu which chooses which type of standard to use.
(0, 0) in top left, current directional system : programming standards
(0, 0) in center, standard slope/gradient (ranges from 0 to undefined) : graph stds.
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#7 2011-03-14 14:58:16
- floppy_gunk
- Scratcher
- Registered: 2008-11-14
- Posts: 500+
Re: Point in Direction 0
LS97 wrote:
(0, 0) in top left, current directional system : programming standards
(0, 0) in center, standard slope/gradient (ranges from 0 to undefined) : graph stds.
No, better programming standards would be to have 0º facing right.
Get it now! 
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#8 2011-03-15 05:05:04
- s_federici
- Scratcher
- Registered: 2007-12-18
- Posts: 500+
Re: Point in Direction 0
Paddle2see wrote:
at the time there were no trig functions in Scratch
I didn't know trig functions were not in first Scratch. But I read a recent paper by the Scratch Team stressing the fact that Scratch has a coordinate/cartesian system. Which is not strictly true at this moment.
LS97 wrote:
We should somehow have an option in some remote menu which chooses which type of standard to use.
I think this is really interesting. I'm working a lot with Jen's excellent BYOB lately, and there are a lot of settings you can select in the Edit menu: sprites off/in Stage, thread safe/unsafe scripts, etc. Settings are saved into each project, so that they don't interfere with how projects work. I would then suggest the following cases:
(0, 0) in top left, current directional system : programming standards
(0, 0) in center, standard Scratch system (for compatibility, or simplicity as someone highltighted)
(0, 0) in center, standard slope/gradient (ranges from 0 to undefined) : graph stds.
Would do you think Team?
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