A SIMPLE IMPLEMENTATION OF NOISE
		     ================================
                 ( From Watt: 3D Graphics)

       procedure initialise_noise;

	 var
	   x,y,z,xx,yy,zz: nrange;

       begin
	  {set up the noise lattice}
	  for x:=0 to max_noise do
	     for y:=0 to max_noise do
		for z:=0 to max_noise do
		   begin
		      noise_table[x,y,z]:=round(random(1)*10000);
		      if x=max_noise then xx:=0 else xx:=x;
		      if y=max_noise then yy:=0 else yy:=y;
		      if z=max_noise then zz:=0 else zz:=z;
		      noise_table[x,y,z]:=noise_table[xx,yy,zz]
		   end;
	end  {initialise_noise};


	function frac(r:real):real;

	begin
	   frac:=r-trunc(r);
	end {frac};


	function noise(x,y,z:real):real;

	  var
	    ix,iy,iz:integer;
	    ox,oy,oz:real;
	    n:integer;
	    n00,n01,n10,n11:real;
	    n0,n1:real;

	begin
	   {offset x,y,z to ensure they are positive}
	   x:=x+15000; y:=y+15000; z:=z+15000;

	   {find lattice coordinates and real offsets}
	   ix:=trunc(x) mod max_noise;
	   iy:=trunc(y) mod max_noise;
	   iz:=trunc(z) mod max_noise;
	   ox:=frac(x); oy:=frac(y); oz:=frac(z);

	   {interpolate to get noise value at (ix+ox,iy+oy,iz++oz)}

	   n:=noise_table[ix,iy,iz];
	   n00:=n+ox*(noise_table[ix+1,iy,iz]-n);
	   n:=noise_table[ix,iy,iz+1];
	   n01:=n+ox*(noise_table[ix+1,iy,iz+1]-n);
	   n:=noise_table[ix,iy+1,iz];
	   n10:=n+ox*(noise_table[ix+1,iy+1,iz]-n);
	   n:=noise_table[ix,iy+1,iz+1];
	   n11:=n+ox*(noise_table[ix+1,iy+1,iz+1]-n);

	   no:=n00+oy*(n10-n00);
	   n1:=n01+oy*(n11-n01);
	   noise:=(n0+oz*(n1-n0))*0.0001;
	end  {noise};