varying vec3 FragVertexCoord;

uniform vec3 campos;

uniform vec3 BoxStart;

uniform vec3 BoxLen;

uniform vec3 sun_dir;
uniform float density_factor;
uniform vec3 sun_light;

uniform sampler2D tex; //cloud density map this case its 2d texture since OpenGL ES 2.0 doesn't support 3d textures...
//61 - 76 pixels from atmosphere scaterring texture (128x128)
uniform vec3 global_ambient; //taken every height pixel and divided by the amount (this case 76-61 = 15)
uniform float ambient_shiness;
uniform float ambient_shade;
uniform vec3 sky_amb;


float modulo(float x, float y)
{
	return x - y * float(int(x/y));
}

vec2 ArrI(int x, int y, int z)
{
int modulo_z = int(modulo(float(z),8.0));
int ax = x+ (modulo_z * 32);
int ay = y+(z / 8) * 32;
return vec2(float(ax)/256.0, float(ay)/256.0);
}

vec3 vectorAB(vec3 A, vec3 B)
{
return B-A;
}

vec3 point_to_grid_cell(vec3 vector)
{
	vec3 dist = vector - BoxStart;
	vec3 result;

result.x =  (dist.x / float(BoxLen.x)) * 32.0;
result.y =  (dist.y / float(BoxLen.y)) * 32.0;
result.z =  (dist.z / float(BoxLen.z)) * 32.0;
          return result;
}




bool RayAABB(vec3 vdir, out vec3 ipoint)
{
    vec3 invR = 1.0 / vdir;
    vec3 tbot = invR * (	BoxStart			-	campos);
    vec3 ttop = invR * (   (BoxStart+BoxLen)	-	campos);
    vec3 tmin = min(ttop, tbot);
    vec3 tmax = max(ttop, tbot);
    vec2 t = max(tmin.xx, tmin.yz);
  float  t0 = max(t.x, t.y);
  t = min(tmax.xx, tmax.yz);
  float  t1 = min(t.x, t.y);
    ipoint = FragVertexCoord + vdir*t0;
    return t0 <= t1;

}

bool same_cell(vec3 a, vec3 b)
{
	if ( int(a.x) != int(b.x) ) return false;
	if ( int(a.y) != int(b.y) ) return false;
	if ( int(a.z) != int(b.z) ) return false;
		
		return true;
}

void main()
{

int i;
float x = BoxLen.x / 32.0;
float y = BoxLen.y / 32.0;
float z = BoxLen.z / 32.0;

float dens = 0.0;
vec3 grid_point;
vec3 grid_point_tmp;
vec3 cell;
vec3 view_dir = normalize(FragVertexCoord - campos);

//find a point that lies on a grid if not return blank color and exit
//that makes everything we can even set that to million but why everything depends on fucking gemoetry we want to display
//since for now i dont have any ideas how to deal with that il make easy loop
bool found = false;
//
//vec3 return_point;
//bool ray_intersects = RayAABB(view_dir, return_point);
//if (ray_intersects)
//{
//	grid_point_tmp = FragVertexCoord+(view_dir*vec3(x,y,z)*0.1);
//    bool a = ( (cell.x <= 32.0) && (cell.y <= 32.0) && (cell.z <= 32.0) );
//    bool b = ( (cell.x >= 0.0)  && (cell.y >= 0.0)  && (cell.z >= 0.0)  );
//if ( ( a && b ) == true ) found = true;
//}
	
	
for (i=0; i < 320; i++)
{
grid_point_tmp = FragVertexCoord+(view_dir*vec3(x,y,z)*float(i));
cell = point_to_grid_cell(grid_point_tmp);
     bool a = ( (cell.x <= 32.0) && (cell.y <= 32.0) && (cell.z <= 32.0) );
     bool b = ( (cell.x >= 0.0)  && (cell.y >= 0.0)  && (cell.z >= 0.0)  );
if ( ( a && b ) == true ) { found = true;  break; }
}




if (found == true)
{
for (i=0; i < 32; i++)
{
grid_point = grid_point_tmp+(view_dir*vec3(x,y,z)*float(i));
cell = point_to_grid_cell(grid_point);

 //make sure we do not go out of grid boundary
if ( (cell.x > 32.0) || (cell.y > 32.0) || (cell.z > 32.0) )  break;
if ( (cell.x < 0.0) || (cell.y < 0.0) || (cell.z < 0.0) ) break;

dens = texture2D( tex, ArrI(int(cell.x+0.5),int(cell.y+0.5),int(cell.z+0.5)) ).r;
if (dens > 0.1) break;

}


//float sum = 0.0;
//vec3 last_cell = cell;
//if (dens > 0.0)
//for (i=0; i < 32; i++)
//{
//
//	/*
//	 * code below prevents from sampling the same cell
//	 * need to fix whole function coz that prevention causes pixeloze :P
//	 */
//grid_point = cell-(sun_dir*float(i));
//if (same_cell(last_cell, grid_point)) continue;
//last_cell = grid_point;
//
//if ( (grid_point.x > 32.0) || (grid_point.y > 32.0) || (grid_point.z > 32.0) ) break;
//if ( (grid_point.x < 0.0) || (grid_point.y < 0.0) || (grid_point.z < 0.0) )  break;
//
//sum = sum + density_factor*texture2D( tex, ArrI(int(grid_point.x),int(grid_point.y),int(grid_point.z)) ).r;
//
//}

float sum = 0.0;
if (dens > 0.0)
for (i=0; i < 32; i++)
{
grid_point = cell-(sun_dir*float(i));

if ( (grid_point.x > 32.0) || (grid_point.y > 32.0) || (grid_point.z > 32.0) ) break;
if ( (grid_point.x < 0.0) || (grid_point.y < 0.0) || (grid_point.z < 0.0) )  break;

sum = sum + density_factor*texture2D( tex, ArrI(int(grid_point.x),int(grid_point.y),int(grid_point.z)) ).r;

}

vec3 darkest_color = sky_amb;//global_ambient * ambient_shade;

vec3 transition = vectorAB(global_ambient, darkest_color);

                              float rc = dens - sum;
                              rc = rc * ambient_shiness;
float intensity = clamp(1.0-rc, 0.0, 1.0);                              
vec3 final = global_ambient + transition*intensity;
 if (dens >0.1)
gl_FragColor = vec4( final, 1.0 );
else
gl_FragColor = vec4( 0.0,0.0,0.0, 0.0 );
//discard;

}

if (found == false)

gl_FragColor = vec4(0.0, 0.0, 0.0, 0.0);



}