local shader = [[ 
extern Image diffuse;
extern number mx; 
extern number my;

vec4 effect(vec4 color, Image texture, vec2 texture_coords, vec2 pixel_coords)
{
   vec3 light_vec = vec3(mx ,my,1);
   vec3 light_direction = light_vec - vec3(pixel_coords, 0);
   float distance = length(light_direction);
   light_direction = normalize(light_direction);

   vec3 normal = Texel(texture, texture_coords).xyz;
   normal.y = 1 - normal.y;
   normal = normalize(mix(vec3(-1), vec3(1), normal));

   //float attenuation = 1/(7e-5*pow(distance, 2));
   float attenuation = 5000/pow(distance, 2);
   //float attenuation = 1;

   float diffuse_term = clamp(attenuation * dot(normal, light_direction), 0.0, 1.0);

   vec3 dark_color = vec3(0.0, 0.0, 1);
   //vec3 light_color = vec3(0.6, 0.6, 0.0);
   vec3 light_color = vec3(0.8, 0.8, 0.0);
   vec3 ambient = mix(dark_color, light_color, diffuse_term) * 0.20;

   // the shaded cel has a light value of 0.5, the light cel has a light value of 1
   float cel_diffuse_term = smoothstep(0.49, 0.52, diffuse_term)/2 + 0.5;
   //float cel_diffuse_term = step(0.5, diffuse_term)/2 + 0.5;

   return vec4((cel_diffuse_term * Texel(diffuse, texture_coords).rgb) + ambient, Texel(texture, texture_coords).a);
   //return vec4(ambient+Texel(diffuse, texture_coords).rgb/100, Texel(texture, texture_coords).a);

}
]]

local jg = jin.graphics
local effect =  jg.Shader(shader) 
local diffuse = jg.Image("treestump_diffuse.png")
local img = jg.Image("treestump.png")

jin.core.onEvent = function(e) 
	if e.type == "quit" then 
		jin.core.quit() 
	end 
end 

jin.core.onUpdate = function() 
	local mx, my = jin.mouse.position() 
	my = 400 - my 
	effect:send("number", "mx", mx)  
	effect:send("number", "my", my)
end 

jin.core.onDraw = function() 
	effect:send("Image", "diffuse", diffuse);
	jg.use(effect)
	jg.draw(img, 250, 200, 5, 5)
	
end