[Edu-sig] News about turtle graphics

Gregor Lingl glingl at aon.at
Thu Jun 29 17:06:58 CEST 2006

Brad Miller schrieb:
> Hi Gregor,
> The more I play with the new xturtle the more I like it.  Thanks!  
> I've been thinking about the following extension to TurtleScreenBase 
> and I wonder what you and others think of the idea.
> I like the fact that the turtle starts out in a coordinate system with 
> 0,0 in the middle of the window, and I like the fact that for 
> beginning students 1 unit == 1 pixel on the screen.  But, I think that 
> after a student has used the turtle to plot a sin or cos curve and 
> learned about scaling the values to make the plot visible in the 
> window it would be nice to place the turtle in a world coordinate 
> system that matched whatever application the student was working on.  
> For example the gravitaion examples could be done in meters.  Let 
> TurtleScreenBase take care of the translation and scaling after for 
> you.  The API could be extended by a single call 
> setWorldCoordinates(llx,lly,ulx,uly) that specifies the world 
> coordinates of the lower left corner of the screen and the upper 
> right.   (This is very similar to the ortho2 call in openGL.  Note, if 
> the student does not call setWorldCoordinates then the turtle 
> functions just as it does now.
> I've already added this capability to the turtle.py that Vern wrote 
> for Python 2.5 and I don't think it would be too hard to add to 
> TurtleScreenBase.  What do you all think?  Would this be a useful 
> addition?  Gregor, is this something you already have on your todo 
> list?  Would you be interested?
I've thought about this,but abandoned it for the moment. The xturtle API 
is already
rather 'fat' as the core developers complained.

I'll appreciate your proposal. So do it, for now as an experiment.
At the moment I'm very busy (and have to concentrate on my Europython talk),
but I've several points to say on this. Please wait until end of next 
week, then
I'll be ready to discuss this in depth.

Thanks again for your idea

(P.S.: When you have done his enhancement, perhaps you could devise
some interesting gravitational systems with real world coordinates?)

> Thanks,
> Brad

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