x-y plane questions

On Sun, Mar 18, 2012 at 10:12 AM, Steve Thomas <[hidden email]> wrote:

Scott,

I started looking at the code and was able to change the tick mark width's for the number lines and playing with the marksWidth/marksHeight.

Part of the issue I was having was that the GraphPaper's line width was 1, but the mark's with was 2, so there was no way to center them.

See samples below:

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.

Also any hints on how can I set the rotational center of the number line to its "0" point?  I can do it with Etoys tiles, But need hints on where would I modify the code and figure out the zero point.

Hi Steve,

I think you can change the rotation center to its 0 point by evaluating this:

For horizontal number lines:

self rotationCenter: ((self left + self offset + (0 - minValue * pixelsPerUnit)) @ (self top + self marksHeight)) - self topLeft / self extent * 1.0

 

For vertical number lines:

self rotationCenter: (self left + self legendsWidth) @ (self bottom - self offset - (0 - minValue * pixelsPerUnit)) - self topLeft / self extent * 1.0

To keep it updated this would have to be hooked up everywhere the number line can change its size. And (maybe) something should be done in case the 0 point is not visible.

Cheers,

Richo

Thanks,

Stephen

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Hi, 

I made a couple of changes to the number lines that I would like you to check:

* 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).

Cheers,

Richo

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

On Sun, Mar 18, 2012 at 6:16 PM, Scott Wallace <[hidden email]> 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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