"Mock26" <nomail@nomail> wrote:
> I would first like to thank Julius Klatte for posting some spiral tutorials
> on his website (http://members.tripod.com/~klatte/pov/helix.html).  All
> credit for the following information belongs to him.
>
> His basic tutorial is as follows:
>
> camera { location <0,2,-10> look_at <0,0,0> }
> light_source { <-30,40,-50> rgb 1 }
> light_source { <60,20,-30> rgb 1 }
>
> #declare Tex = texture { pigment { color rgb <0.95,0.65,0.55> } finish {
> phong 1 phong_size 100 } }
> #declare S = sphere { 0, 0.25 texture { Tex } }
>
> #declare Precision = 0.5;
> union {
>   #declare T = 0;
>   #while (T<360)
>     object { S translate <0,T/180,-2> rotate 4*y*T }
>     #local T = T + 1/Precision;
>   #end
> rotate x*-20 }
>
>
>
> Now, my question is, "Is there is any way to cause each subsequent sphere to
> have a smaller or larger diameter than the one before it?"
>
> Unfortunately, I'm only just dabbling with macro's and such and I'm not all
> that good at it.  I can understand this macro only because Julius Klatte
> explains it very well and "breaking it down" backwards isn't that hard for
> me.  However, trying to create my own macro, even using his as a guide, is
> a bit beyond me at the moment.  I appreciate any help that anyone can offer
> on this, especially if it is in the form of a macro that I can copy and
> paste into my POV file!  Thanks!
>
>
> Take care and have a great day....
>
>
>
> ciao,
> john.


Yes.  Right now you're translating it using the changing variable T.  All
you need to do is also scale it by something that changes with T.  Just
make sure you scale before you translate or the scale will affect the
position of the sphere as well.   E.g:
>     object { S scale 1.5-T/360 translate <0,T/180,-2> rotate 4*y*T }

or whatever numbers look good.

Charles

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