Remove "gray grid" from levelplot

[Jan Marius Hofert]

Hi,

If I use the levelplot function of the lattice library, I always see  
small "squares" in the plot. They indicate the region for which the  
same color is used. If you have a levelplot of a function which is  
evaluated at 25x25 equally-spaced points you obtain 26 squares in x  
and 26 squares in y direction. That does not bother too much (but  
still bothers somehow...), but if you want to plot a function which  
is evaluated at 1000x1000 equally-spaced points, then the "thickness"  
of this gray grid cause the grid lines to hit each other so there is  
no space for the color in the square anymore (since the "squares" are  
actually not visible anymore)... this might change the color of the  
whole levelplot!. (I tried it with the plot of f(x,y)=max(x+y-1,0)  
for x,y in the unit interval, i.e. the Lower Frechet copula). So my  
question is, if it is possible to remove this gray "grid" form the  
levelplot graph?

Thanks in advance

marius