Doubt regarding how to use reconstructShape

I am trying to use the ZC code for general shape analysis. I want to check how well the reconstruction is happening and decide if I should go for higher order. 

function shapeRecon = reconstructShape(gridRes, ZCm, ZPgrid)
gridres is the integer of how many voxels are there along certain axis. 
ZCm is ZC.Moments.Values
But what to put for ZPgrid?? 

Please let me know how to go about it.