DPlot

Question: I have used the PLAYBACK feature to draw a curve "real time" so to speak. But what I'd like to is to draw that same curve in a different way, using an actual animation.

Let me clarify: the curve that I want to draw is the CYCLOID, given by the parametric equations:

x = 4* (t - sin(t)) y = 4* (1 - cos(t))
By using PLAYBACK, I can draw the above curve as some function of time...great....

But what I want to do is to draw that same CYCLOID, starting with a circle, say of radius = 4. Take a point on the circumference of the circle, and now roll the circle on a flat surface for (say) one revolution. The point on the circumference will have traced the same CYCLOID that is given by the parametric equations.
I've tried using POWERPOINT to accomplish the same thing, but was only partially successful. Can DPLOT help me??

http://mathworld.wolfram.com/Cycloid.htm

ps the above website shows exactly what I want to do! I just need to know how to get there, but by using DPOT if possible...

Regards Mike

The only way to do this in DPlot would be to wipe out the circle every time step and redraw it. You can erase curve #1, for example, with

DPlot_Command(DocNum,"[SelectCurve(1)][EditErase()]");

This will work, but I would think would result in a lot of annoying screen flashing since the entire graph will be redrawn every time step.

If you're wanting to build a movie from a sequence of bitmaps instead of showing this in DPlot, that's certainly doable though of course quite a bit more work. Save a bitmap every time step, using a numeric sequence for your BMP-naming scheme, then use something like Video Edit Magic to build your AVI/MPG/whatever movie.

Thank you David for your prompt reply - that animation technique seems analogous to the age-old cartoon animation where the viewer flips thru a series of sequentially altered figures. Doable, but as you stated, probably laborious.

Mike Z

It's definitely a bit of work but the results are better than page-flipping, assuming you save frames frequently enough. Of course the downside is the more frames you save, the larger the file will be.

The wing animation on the Features page was made in this way.

This has my curiosity up about whether the flashing in DPlot will be acceptable or not; I'll try a test of this late tonight and let you know how it turns out.

Look fwd to hearing from you...


Regards Mike Z