function Cosine_Interpolate(var a, var b, var x)
{
	double ft = x * 3.1415927;
	double f = (1 - cos(ft)) * 0.5;
	return  a*(1-f) + b*f;
}

//Perlin Noise Heightmap Generator
///////////////////////////////
//recommended default values:
// size_ 			= 128
// freq_				= 64
// height_min_		= -50
// height_max_		= 200
// iterations_		= 5
// persistence_	= 2
BMAP* perlin_noise(var size_,var freq_,var height_min_,var height_max_,var iteration_,var persistence_)
{
	var format;
	var pixel;
	var px;
	var py;
	var alpha_ = 100;
	var h[2];
	var h1[2];
	var freq;
	VECTOR temp1;
	VECTOR temp2;
	VECTOR temp;
	var i;
	var px1;
	var py1;
	var a;
	var g=0;
	var c=0;
	var t;
	var k;
	var f;
	STRING* temp_str="";
	STRING* temp_str2="";
	var hmaphandle;

	var freq = freq_;
	var hmap_size = size_;
	var height_min = height_min_;
	var height_max = height_max_;
	var var_iteration=iteration_;
	var var_persistence=persistence_;

	BMAP* ptr_bmap_temp = bmap_createblack(size_,size_,24);

	t= 1; c=0; while(c < var_iteration)
	{
		i=0; px=0; py=0; while(i < (hmap_size/(freq/t))*(hmap_size/(freq/t)))
		{
			temp1.x = integer(random((height_max+150)-(height_min+150))+(height_min+150));
			temp1.x = clamp(temp1.x-150, 0, 255);
			format = bmap_lock(ptr_bmap_temp,0);
			pixel = pixel_for_vec(vector(temp1.x,temp1.x,temp1.x),alpha_,format);
			pixel_to_bmap(ptr_bmap_temp, px, py, pixel);
			bmap_unlock(ptr_bmap_temp);
			px+=(freq/t);
			if(px > hmap_size-1)
			{
				px=0;
				py+=(freq/t);
			}
			i+=1;
		}

		a=1/(freq/t); px1=0; py1=0; px=0; py=0; i=0; while(i < (hmap_size-(hmap_size/(freq/t)))*(hmap_size/(freq/t)))
		{
			format = bmap_lock(ptr_bmap_temp,0);
			pixel = pixel_for_bmap(ptr_bmap_temp, px, py);
			pixel_to_vec(temp1,alpha_,format,pixel);
			h[0]=temp1.x;
			pixel = pixel_for_bmap(ptr_bmap_temp, px+(freq/t), py);
			pixel_to_vec(temp1,alpha_,format,pixel);
			h[1]=temp1.x;
			pixel = pixel_for_bmap(ptr_bmap_temp, clamp(px-(freq/t),0,hmap_size-1), py);
			pixel_to_vec(temp1,alpha_,format,pixel);
			h1[0]=temp1.x;
			pixel = pixel_for_bmap(ptr_bmap_temp, clamp(px+((freq/t)*2),0,hmap_size-1), py);
			pixel_to_vec(temp1,alpha_,format,pixel);
			h1[1]=temp1.x;
			temp.x = Cosine_Interpolate(h[0], h[1], a);
			pixel = pixel_for_vec(vector(temp.x,temp.x,temp.x),alpha_,format);
			pixel_to_bmap(ptr_bmap_temp, px+px1+1, py, pixel);
			bmap_unlock(ptr_bmap_temp);
			px1+=1;
			a+=1/(freq/t);
			if(px1 > (freq/t)-2)
			{
				a=1/(freq/t);
				px+=(freq/t);
				px1=0;
				py1+=1;
				if(py1 > (hmap_size/(freq/t))-1)
				{
					px1=0;
					py1=0;
					px=0;
					py+=(freq/t);
					a=1/(freq/t);
				}
			}
			i+=1;
		}	
		
		a=1/(freq/t); px1=0; py1=0; px=0; py=0; i=0; while(i < (hmap_size-(hmap_size/(freq/t)))*(hmap_size))
		{
			format = bmap_lock(ptr_bmap_temp,0);
			pixel = pixel_for_bmap(ptr_bmap_temp, px, py);
			pixel_to_vec(temp1,alpha_,format,pixel);
			h[0]=temp1.x;
			pixel = pixel_for_bmap(ptr_bmap_temp, px, clamp(py+(freq/t), 0, hmap_size-1));
			pixel_to_vec(temp1,alpha_,format,pixel);
			h[1]=temp1.x;
			temp.x = Cosine_Interpolate(h[0], h[1], a);
			pixel = pixel_for_vec(vector(temp.x,temp.x,temp.x),alpha_,format);
			pixel_to_bmap(ptr_bmap_temp, px, py+py1+1, pixel);
			bmap_unlock(ptr_bmap_temp);
			py1+=1;
			a+=1/(freq/t);
			if(py1 > (freq/t)-2)
			{
				a=1/(freq/t);
				py+=(freq/t);
				py1=0;
				px1+=1;
				if(px1 > (hmap_size/(freq/t))-1)
				{
					py1=0;
					px1=0;
					py=0;
					px+=1;
					a=1/(freq/t);
				}
			}
			i+=1;
		}
		
		str_cpy(temp_str, "hmap");
		str_for_num(temp_str2, c);
		str_cat(temp_str, temp_str2);
		str_cat(temp_str, ".tga");
		hmaphandle = file_open_write(temp_str);
		px=0; py=hmap_size-1; i=0; while(i < hmap_size*hmap_size)
		{
			format = bmap_lock(ptr_bmap_temp,0);
			pixel = pixel_for_bmap(ptr_bmap_temp, px, py);
			pixel_to_vec(temp1,alpha_,format,pixel);
			bmap_unlock(ptr_bmap_temp);
			file_asc_write(hmaphandle, temp1.x);
			px+=1;
			if(px > hmap_size-1)
			{
				px=0;
				py-=1;
			}
			i+=1;
		}
		file_close(hmaphandle);

		c+=1;
		t*=var_persistence;
		t = clamp(t, 1, freq);
	}
	
	px=0; py=0; i=0; while(i < hmap_size*hmap_size)
	{
		format = bmap_lock(ptr_bmap_temp,0);
		pixel = pixel_for_vec(vector(0,0,0),alpha_,format);
		pixel_to_bmap(ptr_bmap_temp, px, py, pixel);
		bmap_unlock(ptr_bmap_temp);
		px+=1;
		if(px > hmap_size-1)
		{
			px=0;
			py+=1;
		}
		i+=1;
	}

	f=c-1; k=0; while(k < c)
	{
		str_cpy(temp_str, "hmap");
		str_for_num(temp_str2, f);
		str_cat(temp_str, temp_str2);
		str_cat(temp_str, ".tga");
		hmaphandle = file_open_read(temp_str);
		px=0; py=hmap_size-1; i=0; while(i < hmap_size*hmap_size)
		{
			temp1.x = file_asc_read(hmaphandle);
			format = bmap_lock(ptr_bmap_temp,0);
			pixel = pixel_for_bmap(ptr_bmap_temp, px, py);
			pixel_to_vec(temp2,alpha_,format,pixel);
			temp2.x = (temp2.x+temp1.x)/2;
			temp2.y = temp2.x;
			temp2.z = temp2.x;
			pixel = pixel_for_vec(temp2,alpha_,format);
			pixel_to_bmap(ptr_bmap_temp, px, py, pixel);
			bmap_unlock(ptr_bmap_temp);
			px+=1;
			if(px > hmap_size-1)
			{
				px=0;
				py-=1;
			}
			i+=1;
		}
		file_close(hmaphandle);
		k+=1;
		f-=1;
	}

	i=0; while(i < c)
	{
		str_cpy(temp_str, "hmap");
		str_for_num(temp_str2, i);
		str_cat(temp_str, temp_str2);
		str_cat(temp_str, ".tga");
		file_delete(temp_str);
		i+=1;
	}

	return ptr_bmap_temp;
}