I also stick my nose here.
The notion of "in computer graphics Y goes down" is not as true as some
people think. The graphics you are looking at right now on your computer
most likely to have gone through some programs that use "Y goes up" scheme
(such as GLSL).
Only if you are talking about pixels and raster graphics, you could say
that there is a dominant convention to make Y go down, but in with vectors,
there is no such dominance.
For end-users, why does it matter how actually pixels are stored in the
actual memory? Computer is medium that can simulate anything; so the
decision should not be based on what computer does at the lower levels.
Once we leave from what computer does at low-level, there are math text
books, which are dominantly "Y-up". Why do they have to know two different
conventions? Unless, of course, learning the fact that the coordinate
system is just a convention and can be different.
Also there may be a case where the particular turtle graphics
implementation is tied to the lower level pixel representation. But is
basically mixing different abstraction levels, and unless you want to teach
about mixing abstraction levels, it is a bad starting point.
In summary: the statement "in computer graphics Y goes down" is a wrong
argument for turtle graphics to use Y-down coordinate system. Then, for
turtles and for end-users, there is an existing convention to make Y go
down. So that should be a better default.
On Mon, Jun 18, 2018 at 9:54 AM, Kevin Cole <
kevin.c...@novawebdevelopment.org> wrote:
> Sticking my nose in where it don't belong. ;-) But that's never stopped me
> before. ;-)
>
> First "I are not a teacher". At least, not in any formal sense of the
> word. Second, some would say "I are not a programmer". I don't listen to
> those people.
>
> In spite of the common "in computer graphics Y goes down", does that make
> sense to new learners? I've gotten used to various coordinate systems, but
> the first time I had to work with graph paper and plotting (and, for that
> matter, maps) one goes "up" ("north", "forward") for Y. Then again, maybe
> the average learner isn't quite as flexible these days, and telling them
> after they've gotten used to a system that they have to flip everything
> upside down and backwards isn't a great idea. I attribute my own
> flexibility not to any innate ability but rather to learning during a time
> when architectures OS's and languages were changing fast enough that there
> wasn't time to become set in one's ways.
>
> [Note: Grammatical "mistakes" above are meant as weak -- very weak --
> humor. At least, most are.]
> --
> *Kevin Cole*
> <http://novawebdevelopment.org>
> NOVA Web Development Co-Op
> http://novawebdevelopment.org/
> Arlington, VA
>
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>
>
--
-- Yoshiki
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