private void EnsurePointPairListLength(PointPairList ppl, int length)
{
int delta = length-ppl.Count;
if(delta > 0)
{ // Add additional points.
for(int i=0; i<delta; i++) {
ppl.Add(0.0, 0.0);
}
}
else if(delta < 0)
{ // Remove excess points.
ppl.RemoveRange(length, -delta);
}
}