Nspire and 3D plotting before it was a part of the software

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Can’t be done

In the early times of the Nspire I spent some time on some forums discussion Nspire. Quite many people where angry that Nspire could not do this or could not do that. What most of those people missed was that the Nspire is not designed as a tool for engineers, but as an educational tool.

On the other hand, that I think TI missed is how little extra would be added to satisfy nerds or geeks  (like me to a bit) too.  A few more functions, like the Gamma function (maths geeks love the gamma function), possibly some FFT and Laplace transforms, and 3D graphs (that the Nspire have now but not then).

Having added this would have turned the geeks more positive – and the value of that cannot be underestimated.

Anyhow, one of the things people complained about was the lack of a plot command. I.e. a command that would allow you to, under program control, add graphics elements to a window, like a point or a line. One reason for this anger was that people thought it made it impossible to at least write an own 3D-plot functionality since it was (then) missing.

Anyhow, the geek (or perhaps nerd) part of me thought of that a challenge, so I wrote a “program” that could do just that.

I remember a particular discussion on a forum where someone, yet again, said that the Nspire was a bad product because you could not even program it to do 3D plots. So I said, yes you can, I have just done it, and was immediately called a liar. Would it not have been better to ask me “Ok,could you show me”?  Internet is at times a dark place. I was by the way also called evil  just because I defended the Nspire as an educational tool.

Anyhow, back on track..

How to do what cant be done

 My idea was to use the scatter plot functionality on the Nspire, together with  the dynamic coupling between the data and the graph.  When changing the data in the built in spread sheet, the graph would change too, as in Excel. Then one can choose to connect the dots in the scatter plot. To make several separate parts one can put “_” as data in between the parts. This basically acts as a “Not a number” and will not be plotted.

The little table above could be used to make the following graph.

Not overly impressive, but at least a start.  The idea is now that we could add and remove rows in the tables to add and remove point, and change the numbers to other values to change coordinates. The values could for example be changed by adding a slider, and use the variable value to change the values in the table.

The 3D plotter

This is basically what I did to make the 3D plotter.  I calculated a bunch of points on a square grid using a fuction of the form z=f(x,y), Then I transformed the points to new coordinates using ordinary coordinate transformations (in this case rotations), then I did a perspective transform from 3D to 2D to get the where to plot the points on the screen.  The result looks like this.

The user can change the function, and it will automatically replot the graph. The user can also rotate the graph along all three axes.  If you want to try it you can download a copy here: 3d16.tns.

It was written before the Nspire had colours + I would have done it using more program control if if I would do it again. But anyhow, it shows what can be done.

The program won some kind of “best program” prize “back in the days”.

Up a level : Nspire and Lua
Next page : A bit more on graphing under software controlLast modified: Jan 5, 2019 @ 14:08