local shader = [[ 
extern Image diffuse;
extern vec2 mouse; 
extern number i ; 

vec4 effect(vec4 color, Image texture, vec2 texture_coords, vec2 pixel_coords)
{
   vec3 light_vec = vec3(mouse,1);
   vec3 light_direction = light_vec - vec3(pixel_coords, 0);
   float distance = length(light_direction);
   light_direction = normalize(light_direction) * abs(sin(i));

   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 shader2 = [[ 
extern Image diffuse;
vec4 effect(vec4 color, Image texture, vec2 texture_coords, vec2 pixel_coords)
{
	return Texel(diffuse, texture_coords);
}	
]] 

local jg = jin.graphics
local effect =  jg.Shader(shader) 
local effect2 = jg.Shader(shader2)
local diffuse = jg.Image("treestump_diffuse.png")
local img = jg.Image("treestump.png")
local ww, wh = jg.size() 
local scale = 2 
ww = ww / scale 
wh = wh / scale 
jin.core.onEvent = function(e) 
	if e.type == "quit" then 
		jin.core.quit() 
	end 
end 
local mx, my 
jin.core.onUpdate = function() 
	mx, my = jin.mouse.position() 
	mx = mx / 2 
	my = my / 2
	my = wh - my 
end 
img:setAnchor(16, 16)
local cvs = jg.Canvas(320, 240)
local i = 0
jin.core.onDraw = function() 
	i = i + 0.1
	jg.bind(cvs)
	jg.use(effect)
	effect:send("vec2", "mouse", mx, my)
	effect:send("number", "i", i)
	effect:send("Image", "diffuse", diffuse)
	jg.draw(img, ww / 2, wh / 2, 2, 2)
	jg.unuse()
	jg.use(effect)
	effect:send("Image", "diffuse", diffuse)
	jg.draw(img, ww / 3, wh / 2, 2, 2)	
	jg.unuse() 
	jg.unbind()	
	jg.draw(cvs, 0, 0, 2, 2)
end