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MathGroup Archive 2002

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Re: Mathematica Animation Problem

  • To: mathgroup at smc.vnet.net
  • Subject: [mg35449] Re: [mg35432] Mathematica Animation Problem
  • From: BobHanlon at aol.com
  • Date: Sat, 13 Jul 2002 03:48:20 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

In a message dated 7/12/02 6:55:08 AM, tofesi at web.de writes:

>I hope someone can give me advice concerning the following Mathematica
>(Version 4.1) problem:
>
>I am trying to produce an animation of a circular "walk" around a 3D
>plot. I get the animation, but it looks like sometimes I get nearer to
>the plot and sometimes the plot looks more distant, so that I don't
>get the impression of walking on a circle.
>
>My guess is that I have not yet understood how the options
>"ViewCenter" and "ViewPoint" work.
>
>So here is what I wrote to produce the image sequence:
>
>For [alpha = 0.0, alpha < 2 Pi, alpha = alpha + 0.1,
>  Plot3D[ Exp[-(x^2 + y^2)], {x, -2, 2}, {y, -2, 2}, 
>          {ViewCenter -> {0, 0, 0}, 
>           ViewPoint -> {5 Cos[alpha], 5 Sin[alpha], 0.5}}]]
>
>So all viewpoints should lie on a circle of radius 5 around the origin
>and with a constant height of 0.5. But the visual impression is
>different, as decribed above. Anyone knows what's wrong?
>

For[alpha=0, alpha<2 Pi, alpha=alpha+0.1,
    Plot3D[Exp[-(x^2+y^2)],
      {x,-2,2},{y,-2,2},
      ViewPoint->
        {5 Cos[alpha], 5 Sin[alpha], 0.5},
 
      SphericalRegion->True,
      Ticks->None]];

However, you are calculating the plot for each view.  Alternatively,

plt=Plot3D[Exp[-(x^2+y^2)],
      {x, -2, 2}, {y, -2, 2},
 
      DisplayFunction->Identity];

For[alpha=0, alpha<2 Pi, alpha=alpha+0.1,
    Show[plt,
      ViewPoint->
        {5 Cos[alpha], 5 Sin[alpha], 0.5},
 
      SphericalRegion->True,
      Ticks->None,
      DisplayFunction->$DisplayFunction]];


Bob Hanlon
Chantilly, VA  USA


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