[etoys-dev] x-y plane questions

Ricardo Moran richi.moran at gmail.com
Sun Mar 18 20:52:41 EDT 2012


I made a couple of changes to the number lines that I would like you to
* I added two tiles: "transform to pixel" and "transform to graph" (the
names could be improved but I didn't know how to name them). This tiles
take a number as a parameter and return it transformed to the other
coordinate system. It's a general way of using the number lines and I think
it could be very useful.
* I changed "x on graph" and "y on graph" to take into account the object's
rotation center. However, I could have messed up with this and it could
have undesired side effects, so testing would be needed.

I attached a project that uses the x-y plane for ploting bars (open it on
Etoys 5.0 beta 2).


P.S. I just found the "attached watcher" option and it's great!

On Sun, Mar 18, 2012 at 6:16 PM, Scott Wallace <scott.wallace at squeakland.org
> wrote:

> On Mar 18, 2012, at 6:12 AM, Steve Thomas wrote:
> > But I couldn't figure out how to change the pixel width of the graph
> paper, could you point me in the right direction, thanks
> Hi, Steve,
> Open the attached fileout in a change-list browser (click "changes" button
> in file-list); the diffs that will show between the versions in the fileout
> and what's in the image will answer your question :)  In the versions I've
> sent, the grid-line-width is parameterized instead of constant, and in both
> cases, for illustration, that grid-line-width parameter is set to 2.
> If wider-than-single-pixel grid lines seem viable and useful and don't
> introduce new issues (need to be sure to test everything with "scale to
> fit" turned on), perhaps we could add the grid-line-width as another
> parameter in the graph-paper panel.
> With scale-to-fit on, it seems that with both 1-pixel and 2-pixel
> grid-line widths we end up with round-off phenomenon such that some of the
> grid lines are thicker than others.  I'm not sure if this is an intractable
> mathematical consequence or something fixable, but I suspect that it's the
> former.
>  -- Scott
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