// -*-C++-*-

// Ambient term comes in gl_Color.rgb.
#version 120

varying vec4 diffuse_term;
varying vec3 normal;
varying vec3 ecViewDir;
varying vec3 VTangent;

uniform float shade_effect;
uniform float sun_angle;
uniform float air_pollution;

uniform bool use_overlay;
uniform bool use_cloud_normals;

uniform sampler2D texture;
uniform sampler2D structure_texture;

float Noise2D(in vec2 coord, in float wavelength);
vec3 filter_combined (in vec3 color) ;


float add_cosines (in float cos1, in float cos2, in float sign)
{

float sin1 = sqrt(1.0 - pow(cos1, 2.0));
float sin2 = sqrt(1.0 - pow(cos2, 2.0));

return cos1 * cos2 + sign *  sin1 * sin2;

}


void main()
{
    vec3 n;
    float NdotL, NdotHV, NdotLraw;
    vec4 color = gl_Color;
    vec3 lightDir = gl_LightSource[0].position.xyz;

    vec3 halfVector = normalize(normalize(lightDir) + normalize(ecViewDir));
    vec4 texel;
    vec4 ref_texel;
    vec4 structureTexel;

    vec4 fragColor;
    vec4 specular = vec4(0.0, 0.0, 0.0, 0.0);

    n = normalize(normal);

	
    vec3 light_specular = vec3 (1.0, 1.0, 1.0);
    NdotL = dot(n, normalize(lightDir));
    NdotLraw = NdotL;
    NdotL = smoothstep(-0.2,0.2,NdotL);	

    float intensity = length(diffuse_term.rgb);

    vec3 dawn_color = mix (vec3 (1.0,0.7,0.4), vec3 (1.0,0.4,0.2), air_pollution);

    vec3 dawn = intensity * 1.2 * normalize (dawn_color);
	
    vec4 diff_term = mix(vec4(dawn, 1.0), diffuse_term, smoothstep(0.0, 0.45, NdotL));


    vec2 grad_dir = vec2 (1.0, 0.0);

    vec3 tangent = normalize(VTangent);
    vec3 binormal = cross(n, tangent);
    float NdotL2 = 0.0;

   if (use_cloud_normals)
	{
   	vec2 sun2d = vec2 (0.0, 1.0);

  	float xOffset = -1.0 * dot(normalize(lightDir), tangent);
   	float yOffset = -1.0 * dot(normalize(lightDir), binormal);	
	
	grad_dir = normalize (vec2 (xOffset, yOffset));

	vec4 comp_texel = texture2D(texture, gl_TexCoord[0].st - 0.0005 * grad_dir);

	float slope = shade_effect * (comp_texel.a - ref_texel.a);
	float sign = -1.0;
	if (slope < 0.0) {sign = 1.0;}
	
	vec2 snormal = normalize(vec2 (slope, 1.0));

	NdotL2 = dot (snormal, sun2d);
    	NdotL = add_cosines(NdotL, NdotL2, sign );
	}

        color += diff_term * max(NdotL, 0.15) ;



	

	color.rgb *= smoothstep(-0.2, -0.1, NdotLraw);
	//
	
	
    
    color.a = diffuse_term.a;
    color = clamp(color, 0.0, 1.0);
    texel = texture2D(texture, gl_TexCoord[0].st);



    ref_texel = texel;
    structureTexel = texture2D(structure_texture, 20.0 * gl_TexCoord[0].st);

    float noise = Noise2D( gl_TexCoord[0].st, 0.01);
    noise += Noise2D( gl_TexCoord[0].st, 0.005);
    noise += Noise2D( gl_TexCoord[0].st, 0.002);
	

    vec4 noiseTexel = vec4 (1.0,1.0,1.0, 0.5* noise * texel.a);
    structureTexel = mix(structureTexel, noiseTexel,noiseTexel.a);




    if (use_overlay) 
	{
	texel = vec4(structureTexel.rgb, smoothstep(0.0, 0.5,texel.a) * structureTexel.a);
	}


    fragColor = color * texel;
    fragColor.rgb = filter_combined(fragColor.rgb);

    gl_FragColor = clamp(fragColor, 0.0, 1.0);


}