       Re: Mathematica Animation Problem

• To: mathgroup at smc.vnet.net
• Subject: [mg35452] Re: [mg35432] Mathematica Animation Problem
• From: "Eric L. Strobel" <fyzycyst at comcast.net>
• Date: Sat, 13 Jul 2002 03:48:25 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

```on 7/12/02 4:28 AM, Tobi at tofesi at web.de wrote:

> Dear all,
>
> 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?
>

If I walk a circular path about a square object, when I pass the corners,
I'm nearer to the square than at other times.  Is this what you're talking
about?  If so, then you'd have to make the viewpoint follow a path such that
the apparent angle subtended by the plot is a constant.  (In order to avoid
this perceptual problem.)

- Eric.

--

Eric Strobel (fyzycyst at NOSPAM^mailaps.org)

=====================================================================
END RADIOPHOBIA!!!                          More nukes, less kooks!!!
=====================================================================

```

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