Gradient map for shatter

Question

Hi
I've ceated this shatter map with After effects.
http://img388.imageshack.us/img388/2644/bild2yr8.png
It's made out of 256 solids via Scripts and expressions.
Now,how can i create a gradient map so i have got control over all pieces .
I'd like to reveal them in a specific order.First row reveals from left to right then second row from right to left and so on...one row after the other.
Any expressions to give them a slight color change?

Answer 1

Position:
//===begin expression===
//grid size
gSize=16;
//grid spacing
gSpace=30;
//rows and columns
pRow=Math.ceil(index/gSize);
pCol=Math.ceil(index-(pRow-1)/gSize);
//positions
X=pCol*gSpace-gSpace*gSize*(pRow-1);
Y=pRow*gSpace;
[X,Y]
//===end expression===
Opacity:
//===begin expression===
//grid size
gSize=16;
//rows and columns
pRow=Math.ceil(index/gSize);
pCol=Math.ceil(index-(pRow-1)/gSize);
iStart=pRow*gSize-(gSize-1);
iEnd=pRow*gSize;
oStart=100/Math.pow(gSize,2)*(pRow-1)*gSize;
oEnd=100/Math.pow(gSize,2)*pRow*gSize;
if(pRow % 2 == 0)
mOpa = linear(index,iStart,iEnd,oStart,oEnd) //even row
else
mOpa = linear(index,iStart,iEnd,oEnd,oStart) //odd row
[mOpa]
//===end expression===
Use this in a pre-comp with white solids on top of a black solid to generate a b/w gradient.
Mylenium