I'm trying to edit an expression which makes a perfect 3D Xmas tree spiral which a particle generator then follows.

I know this subject has come up before and I have tried to use some tips from this thread

http://forums.creativecow.net/thread/227/12276
However nothing looks as good as my first attempt.

So the current expression begins at the top of tree and builds outwards and downwards.

I need the expression to start at the bottom and build upwards and inwards.

Original Expression:

radius=-time*30

angle=-time*300;

x=radius*Math.cos(degreesToRadians(angle));

y=radius*Math.sin(degreesToRadians(angle));

z=time*50

center=[190,400,100];

add(center,[x,y,z]);

Any help/point in the right direction would be greatly appreciated.