On Sun, 18 Apr 1999 22:39:41 +0100, "Andrew Cocker"
<and### [at] acockerfreeservecouk> wrote:

>Hi,
>
>Starting with the following code:
>
>sphere {
>    <0,0,0>,1
>    scale <0.25,1,0.25>
>    translate <-0.5,0,0>
>    texture { MyTexture }
>}
>
>plane
>
>    y, -1
>    texture { MyTexture }
>}
>
>I wish to rotate the sphere clockwise on the z axis by 180 degrees, at the same time
>translating it along the x axis by 1 unit, so that it ends up at <0.5,0,0>.
>The question is, how do I mathematically model the vertical motion so that the shape
>appears to be rolling along the plane?NOTE: I may wish to alter the scale of the
shape
>*during* the anim, so this must be taken into account in the equation.
>
>Any help appreciated.

Now, a 180 degrees' roll of this objects makes for a x translation of
3.14159265, if you want it to roll correctly. If I understand your
question correctly, you are trying to model the behaviour of, say, an
unrolling rug, right? I mean, it moves, rolls, gets smaller, and stays
on the ground all at the same time.

The radius is a simple linear function:
 r(clock) = startRad - clock*(startRad - endRad).

The y coordinate of the center is -1 + radius.

The x coordinate is found by integrating 2*pi*r(clock)*dclock in the
range from 0 to clock.

Am I getting the problem right? Is this of any help?

---------
Peter Popov
ICQ: 15002700

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