#version 450

uniform sampler2D tex;

uniform vec4 diffuse;
uniform vec4 specular;
uniform float shininess;

varying vec3 pos;
varying vec3 normal;
varying vec3 ldir;
varying vec2 tex_coord;

// const float fog_density = 0.005;
uniform float fog_density;
const vec4 sky_color = vec4(0.35, 0.5, 0.65, 1.0);

out vec4 color;

void main()
{
	vec3 p = normalize(pos); // view space dir
	vec3 n = normalize(normal);
	vec3 l = normalize(ldir);

	vec3 r = normalize(-reflect(l, n));
	vec3 vdir = normalize(-p);

	float cdiff = max(dot(l, n), 0.0);
	float cspec = pow(max(dot(r, vdir), 0.0), shininess);

	float dist = -pos.z;
	float fog = clamp(exp(-fog_density * dist), 0.0, 1.0);

	vec4 texel = texture2D(tex, tex_coord);

	vec4 object_color;
	object_color.xyz = diffuse.xyz * cdiff * texel.xyz + specular.xyz * cspec;
	object_color.w = 1.0;

	color = mix(sky_color, object_color, fog);
}