Line Tracing

[Roger Guay]

Thanks to all who have responded to this Line tracing thing.  Here is 
another iteration.

> Date: Sat, 1 Feb 2003 04:51:22 -0800
> To: use-revolution at lists.runrev.com
> From: Jim Hurley <jhurley at infostations.com>
> Subject: Line tracing

> I think I see the problem. It is not a difficulty with refreshing the
> screen but the very large sampling times in the  trajectory
> equations. If you  change "add 1 to T" to "add .05 to T" you  will
> get a much smoother motion.  At least it does on my PowerBook running
> OS 8.6

I have no problem with the motion . . . it's very smooth on my new iMac 
and several PC's I use. But you're right about the sampling time being  
a critical consideration.

> But I thought you wanted a line drawn in the  wake of the graphic  
> motion?

Yes, that's exactly what I am trying to do.  What I am trying to do 
reminds me of an oscilloscpoe where the persistence of the screen 
results in a line/trace from a moving spot on the screen.

> I couldn't try your sound effects. They should add a nice touch to
> the visual. I have seen discussions on this list of problems with
> sound effects timing; that could be a conflict for you. I can't help
> you there.

Since you're interested, I've emailed you privately to offer the 
download of my stack along with it's sound files.
I've experienced no timing problems with the sounds on my machines.

> You  will find a number of these problems in dynamics illustrated in
> the demo on the RR web site on the Education page including  the
> projectile motion you are working on as well as planetary motion,
> Kepler's 2nd law (planets sweep out equal areas in equal times), the
> voyager sling shot effect as it moved around Jupiter and others. The
> graphic I use there is the turtle, which I represent with an arrow
> icon, which allows me to show heading as well as position. But it is
> easily modified to move any one or more RR controls (buttons, fields,
> graphics, images, etc.). You have the option of leaving a line in the
> turtle's wake or not.

I've briefly looked at your TurtleGraphicsDemo and I'm very impressed.  
I haven't had time to understand the "Turtle" aspect yet, but I will 
have a closer look.  I've been toying with the idea of simulating a 
typical Science Museum Foucault Pendulum, where a beautiful pattern is 
traced in the sand by the pendulum.  I would like to generate those 
patterns by running the equation of motion of the Foucault Pendulum.  I 
think this is not going to be easy because if I recall correctly, this 
is a non-linear differential equation.  But, I'm ignorant enough to 
proceed anyway.

Thanks, Roger