"drape.color" <-
function (z, 
 col=tim.colors(64),zlim=NULL,transperent.color="white") 
{
#slight increase for range 
  eps<- 1e-7
  
# range if zlim not supplied
  if( is.null( zlim)){ zlim <-  range( c(z), na.rm=TRUE)}

  NC<- length( col)
  M<- nrow(z)
  N<- ncol(z)
# find average z value for a facet
  zm<- ( z[1:(M-1),1:(N-1)] + z[2:M, 1:(N-1)] + z[1:(M-1),2:N] + z[2:M,2:N] )/4
# spacing for grid to assign  colors
# 1+eps included so that if z== zlim[2] it gets a color
  dz<- (zlim[2]*(1+eps)- zlim[1])/NC
# discretize the z-valuez
  zcol<- floor( (zm -zlim[1])/dz  +1)
# assign colors if in range 1;NC otherwise it is the transperent color
  
 ifelse( zcol >NC, transperent.color, col[zcol])


}