// -*- mode: C; -*-
// Licence: GPL v2
// Authors: Frederic Bouvier and Gijs de Rooy
// with major additions and revisions by
// Emilian Huminiuc and Vivian Meazza 2011
// ported to Atmospheric Light Scattering 
// by Thorsten Renk, 2013
#version 120

varying	vec3 	VBinormal;
varying	vec3 	VNormal;
varying	vec3 	VTangent;
varying	vec3 	rawpos;
varying	vec3 	reflVec;
varying	vec3 	vViewVec;
varying vec3	vertVec;

varying	float	alpha;

uniform sampler2D BaseTex;
uniform sampler2D LightMapTex;
uniform sampler2D NormalTex;
uniform sampler2D ReflFresnelTex;
uniform sampler2D ReflMapTex;
//uniform sampler2D ReflRainbowTex;
uniform sampler3D ReflNoiseTex;
uniform samplerCube Environment;
uniform sampler2D GrainTex;

uniform int dirt_enabled;
uniform int dirt_multi;
uniform int lightmap_enabled;
uniform int lightmap_multi;
uniform int nmap_dds;
uniform int nmap_enabled;
uniform int refl_enabled;
uniform int refl_map;
uniform int shader_qual;
uniform int grain_texture_enabled;

uniform float amb_correction;
uniform float dirt_b_factor;
uniform float dirt_g_factor;
uniform float dirt_r_factor;
uniform float lightmap_a_factor;
uniform float lightmap_b_factor;
uniform float lightmap_g_factor;
uniform float lightmap_r_factor;
uniform float nmap_tile;
uniform float refl_correction;
uniform float refl_fresnel;
uniform float refl_noise;
uniform float refl_rainbow;
uniform float grain_magnification;


uniform float avisibility;			
uniform float cloud_self_shading;
uniform float eye_alt;
uniform float ground_scattering;		
uniform float hazeLayerAltitude; 		
uniform float moonlight;			
uniform float overcast;				
uniform float scattering;			
uniform float terminator;			
uniform float terrain_alt; 			
uniform float visibility;			

// constants needed by the light and fog computations ###################################################

const float EarthRadius = 5800000.0;
const float terminator_width = 200000.0;

uniform vec3 lightmap_r_color;
uniform vec3 lightmap_g_color;
uniform vec3 lightmap_b_color;
uniform vec3 lightmap_a_color;

uniform vec3 dirt_r_color;
uniform vec3 dirt_g_color;
uniform vec3 dirt_b_color;

// uniform mat4 osg_ViewMatrixInverse;
// uniform mat4 osg_ViewMatrix;

float light_func (in float x, in float a, in float b, in float c, in float d, in float e)
{
	if (x > 30.0) {return e;}
	if (x < -15.0) {return 0.0;}
	return e / pow((1.0 + a * exp(-b * (x-c)) ),(1.0/d));
}

float fog_func (in float targ, in float altitude)
{
	float fade_mix;

	targ = 1.25 * targ * smoothstep(0.04,0.06,targ); // need to sync with the distance to which objects are drawn unfogged

	if (altitude < 30000.0)
		{return exp(-targ - targ * targ * targ * targ);}
	else if (altitude < 50000.0)
		{
		fade_mix = (altitude - 30000.0)/20000.0;
		return fade_mix * exp(-targ*targ - pow(targ,4.0)) + (1.0 - fade_mix) * exp(-targ - pow(targ,4.0));	
		}
	else 
		{
		return exp(- targ * targ - pow(targ,4.0));
		}

}


void main (void)
{
	vec4 texel      = texture2D(BaseTex, gl_TexCoord[0].st);
	vec4 nmap       = texture2D(NormalTex, gl_TexCoord[0].st * nmap_tile);
	vec4 reflmap    = texture2D(ReflMapTex, gl_TexCoord[0].st);
	vec4 noisevec   = texture3D(ReflNoiseTex, rawpos.xyz);
	vec4 lightmapTexel = texture2D(LightMapTex, gl_TexCoord[0].st);

	vec4 grainTexel; 

	vec3 mixedcolor;
	vec3 N = vec3(0.0,0.0,1.0);
	float pf = 0.0;
///some generic light scattering parameters 
	vec3 shadedFogColor = vec3(0.65, 0.67, 0.78);
	vec3 moonLightColor = vec3 (0.095, 0.095, 0.15) * moonlight;
	float alt = eye_alt; 					
	float effective_scattering = min(scattering, cloud_self_shading);

	
/// BEGIN geometry for light

	vec3 up = (gl_ModelViewMatrix * vec4(0.0,0.0,1.0,0.0)).xyz;
	//vec4 worldPos3D = (osg_ViewMatrixInverse * vec4 (0.0,0.0,0.0, 1.0));
	//worldPos3D.a = 0.0;
	//vec3 up = (osg_ViewMatrix * worldPos3D).xyz;
	float dist = length(vertVec);
	float vertex_alt = max(100.0,dot(up, vertVec) + alt);
	float vertex_scattering = ground_scattering + (1.0 - ground_scattering) * smoothstep(hazeLayerAltitude -100.0, hazeLayerAltitude + 100.0, vertex_alt); 


	vec3 lightHorizon = gl_LightSource[0].position.xyz - up * dot(up,gl_LightSource[0].position.xyz);
	float yprime = -dot(vertVec, lightHorizon);
	float yprime_alt = yprime - sqrt(2.0 * EarthRadius * vertex_alt);
	float lightArg = (terminator-yprime_alt)/100000.0;

	float earthShade = 0.6 * (1.0 - smoothstep(-terminator_width+ terminator, terminator_width + terminator, yprime_alt)) + 0.4;

	float mie_angle;
	if (lightArg < 10.0)
    		{mie_angle = (0.5 *  dot(normalize(vertVec), normalize(gl_LightSource[0].position.xyz)) ) + 0.5;}
  	else 
		{mie_angle = 1.0;}
		
	float fog_vertex_alt = max(vertex_alt,hazeLayerAltitude);
	float fog_yprime_alt = yprime_alt;
	if (fog_vertex_alt > hazeLayerAltitude)
		{
		if (dist > 0.8 * avisibility)
			{
			fog_vertex_alt = mix(fog_vertex_alt, hazeLayerAltitude, smoothstep(0.8*avisibility, avisibility, dist));
			fog_yprime_alt = yprime -sqrt(2.0 * EarthRadius * fog_vertex_alt);
			}
		}
	else
		{
		fog_vertex_alt = hazeLayerAltitude;
		fog_yprime_alt = yprime -sqrt(2.0 * EarthRadius * fog_vertex_alt);
		}

	float fog_lightArg = (terminator-fog_yprime_alt)/100000.0;
	float fog_earthShade = 0.9 * smoothstep(terminator_width+ terminator, -terminator_width + terminator, fog_yprime_alt) + 0.1;

	float ct = dot(normalize(up), normalize(vertVec));

/// END geometry for light
	
	
/// BEGIN light
	vec4 light_diffuse;
	vec4 light_ambient;
	float intensity;

    light_diffuse.b = light_func(lightArg, 1.330e-05, 0.264, 3.827, 1.08e-05, 1.0);
    light_diffuse.g = light_func(lightArg, 3.931e-06, 0.264, 3.827, 7.93e-06, 1.0);
    light_diffuse.r = light_func(lightArg, 8.305e-06, 0.161, 3.827, 3.04e-05, 1.0);
    light_diffuse.a = 1.0;
    light_diffuse = light_diffuse * vertex_scattering;
	
    light_ambient.r = light_func(lightArg, 0.236, 0.253, 1.073, 0.572, 0.33);
    light_ambient.g = light_ambient.r * 0.4/0.33; 
    light_ambient.b = light_ambient.r * 0.5/0.33; 
    light_ambient.a = 1.0;

	if (earthShade < 0.5)
		{
		intensity = length(light_ambient.rgb); 
		light_ambient.rgb = intensity * normalize(mix(light_ambient.rgb,  shadedFogColor, 1.0 -smoothstep(0.1, 0.8,earthShade) ));
		light_ambient.rgb = light_ambient.rgb +   moonLightColor *  (1.0 - smoothstep(0.4, 0.5, earthShade));

		intensity = length(light_diffuse.rgb); 
		light_diffuse.rgb = intensity * normalize(mix(light_diffuse.rgb,  shadedFogColor, 1.0 -smoothstep(0.1, 0.7,earthShade) ));
		}


/// END light	
	
/// BEGIN grain overlay
	if (grain_texture_enabled > 0)
		{
		grainTexel = texture2D(GrainTex, gl_TexCoord[0].st * grain_magnification);
		texel.rgb = mix(texel.rgb, grainTexel.rgb,  grainTexel.a );
		}
/// END grain overlay	

///BEGIN bump
 	if (nmap_enabled > 0 && shader_qual > 2){
	N = nmap.rgb * 2.0 - 1.0;
		N = normalize(N.x * VTangent + N.y * VBinormal + N.z * VNormal);
		if (nmap_dds > 0)
			N = -N;
 	} else {
 		N = normalize(VNormal);
 	}
///END bump
	vec4 reflection = textureCube(Environment, reflVec * dot(N,VNormal));
	vec3 viewVec = normalize(vViewVec);
	float v      = abs(dot(viewVec, normalize(VNormal)));// Map a rainbowish color
	vec4 fresnel = texture2D(ReflFresnelTex, vec2(v, 0.0));
	//vec4 rainbow = texture2D(ReflRainbowTex, vec2(v, 0.0));

	float nDotVP = max(0.0, dot(N, normalize(gl_LightSource[0].position.xyz)));
	float nDotHV = max(0.0, dot(N, normalize(gl_LightSource[0].halfVector.xyz)));
	//glare on the backside of tranparent objects
	if ((gl_FrontMaterial.diffuse.a < 1.0 || texel.a < 1.0)
		&& dot(N, normalize(gl_LightSource[0].position.xyz)) < 0.0) {
		nDotVP = max(0.0, dot(-N, normalize(gl_LightSource[0].position.xyz)));
		nDotHV = max(0.0, dot(-N, normalize(gl_LightSource[0].halfVector.xyz)));
	}

	if (nDotVP == 0.0)
		pf = 0.0;
	else
		pf = pow(nDotHV, gl_FrontMaterial.shininess);

	//vec4 Diffuse  = gl_LightSource[0].diffuse * nDotVP;
	vec4 Diffuse  = light_diffuse * nDotVP;
	//vec4 Specular = gl_FrontMaterial.specular * gl_LightSource[0].specular * pf;
	vec4 Specular = gl_FrontMaterial.specular * light_diffuse * pf;

	vec4 color = gl_Color + Diffuse * gl_FrontMaterial.diffuse;
	color += Specular * gl_FrontMaterial.specular * nmap.a;
	color = clamp( color, 0.0, 1.0 );

////////////////////////////////////////////////////////////////////
//BEGIN reflect
////////////////////////////////////////////////////////////////////
	if (refl_enabled > 0 && shader_qual > 1){
		float reflFactor = 0.0;
		float transparency_offset = clamp(refl_correction, -1.0, 1.0);// set the user shininess offset

		if(refl_map > 0){
			// map the shininess of the object with user input
			//float pam = (map.a * -2) + 1; //reverse map
			reflFactor = reflmap.a + transparency_offset;
		} else if (nmap_enabled > 0 && shader_qual > 2) {
			// set the reflectivity proportional to shininess with user input
			reflFactor = gl_FrontMaterial.shininess * 0.0078125 * nmap.a + transparency_offset;
		} else {
			reflFactor = gl_FrontMaterial.shininess* 0.0078125 + transparency_offset;
		}
		reflFactor = clamp(reflFactor, 0.0, 1.0);

		// add fringing fresnel and rainbow effects and modulate by reflection
		vec4 reflcolor = reflection;//mix(reflection, rainbow, refl_rainbow * v);
		reflcolor += Specular * nmap.a;
		vec4 reflfrescolor = mix(reflcolor, fresnel, refl_fresnel  * v);
		vec4 noisecolor = mix(reflfrescolor, noisevec, refl_noise);
		vec4 raincolor = vec4(noisecolor.rgb * reflFactor, 1.0);
		raincolor += Specular * nmap.a;
		raincolor *= light_diffuse;
		mixedcolor = mix(texel, raincolor, reflFactor).rgb;
 	} else {
 		mixedcolor = texel.rgb;
 	}
 	/////////////////////////////////////////////////////////////////////
 	//END reflect
 	/////////////////////////////////////////////////////////////////////

 	//////////////////////////////////////////////////////////////////////
 	//begin DIRT
 	//////////////////////////////////////////////////////////////////////
 	if (dirt_enabled > 0.0){
		vec3 dirtFactorIn = vec3 (dirt_r_factor, dirt_g_factor, dirt_b_factor);
		vec3 dirtFactor = reflmap.rgb * dirtFactorIn.rgb;
		//dirtFactor.r = smoothstep(0.0, 1.0, dirtFactor.r);
		mixedcolor.rgb = mix(mixedcolor.rgb, dirt_r_color, smoothstep(0.0, 1.0, dirtFactor.r));
		if (dirt_multi > 0) {
			//dirtFactor.g = smoothstep(0.0, 1.0, dirtFactor.g);
			//dirtFactor.b = smoothstep(0.0, 1.0, dirtFactor.b);
			mixedcolor.rgb = mix(mixedcolor.rgb, dirt_g_color, smoothstep(0.0, 1.0, dirtFactor.g));
			mixedcolor.rgb = mix(mixedcolor.rgb, dirt_b_color, smoothstep(0.0, 1.0, dirtFactor.b));
		}
	}
	//////////////////////////////////////////////////////////////////////
	//END Dirt
	//////////////////////////////////////////////////////////////////////


	// set ambient adjustment to remove bluiness with user input
	float ambient_offset = clamp(amb_correction, -1.0, 1.0);
	//vec4 ambient = gl_LightModel.ambient + gl_LightSource[0].ambient;
	vec4 ambient = gl_LightModel.ambient + light_ambient;
	vec4 ambient_Correction = vec4(ambient.rg, ambient.b * 0.6, 1.0)
							  * ambient_offset ;
	ambient_Correction = clamp(ambient_Correction, -1.0, 1.0);

	color.a = texel.a * alpha;
	vec4 fragColor = vec4(color.rgb * mixedcolor + ambient_Correction.rgb, color.a);

	fragColor += Specular * nmap.a;

//////////////////////////////////////////////////////////////////////
// BEGIN lightmap
//////////////////////////////////////////////////////////////////////
	if ( lightmap_enabled >= 1 ) {
		vec3 lightmapcolor = vec3(0.0);
		vec4 lightmapFactor = vec4(lightmap_r_factor, lightmap_g_factor,
								  lightmap_b_factor, lightmap_a_factor);
		lightmapFactor = lightmapFactor * lightmapTexel;
		if (lightmap_multi >0 ){
			lightmapcolor = lightmap_r_color * lightmapFactor.r +
			                lightmap_g_color * lightmapFactor.g +
			                lightmap_b_color * lightmapFactor.b +
			                lightmap_a_color * lightmapFactor.a ;
		} else {
			lightmapcolor = lightmapTexel.rgb * lightmap_r_color * lightmapFactor.r;
		}
		fragColor.rgb = max(fragColor.rgb, lightmapcolor * gl_FrontMaterial.diffuse.rgb * mixedcolor);
	}
//////////////////////////////////////////////////////////////////////
// END lightmap
/////////////////////////////////////////////////////////////////////


/// BEGIN fog amount

float transmission;
float vAltitude;
float delta_zv;
float H;
float distance_in_layer;
float transmission_arg;
float eqColorFactor;

float delta_z = hazeLayerAltitude - eye_alt;

if (dist > max(40.0, 0.04 * min(visibility,avisibility))) 
	{
	if (delta_z > 0.0) // we're inside the layer
		{
		if (ct < 0.0) // we look down 
			{
			distance_in_layer = dist;
			vAltitude = min(distance_in_layer,min(visibility, avisibility)) * ct;
			delta_zv = delta_z - vAltitude;
			}
		else 	// we may look through upper layer edge
			{
			H = dist * ct;
			if (H > delta_z) {distance_in_layer = dist/H * delta_z;}
			else {distance_in_layer = dist;}
			vAltitude = min(distance_in_layer,visibility) * ct;
			delta_zv = delta_z - vAltitude;	
			}
		}
	else // we see the layer from above, delta_z < 0.0
		{	
		H = dist * -ct;
		if (H  < (-delta_z)) // we don't see into the layer at all, aloft visibility is the only fading
			{
			distance_in_layer = 0.0;
			delta_zv = 0.0;
			}		
		else
			{
			vAltitude = H + delta_z;
			distance_in_layer = vAltitude/H * dist; 
			vAltitude = min(distance_in_layer,visibility) * (-ct);
			delta_zv = vAltitude;
			} 
		}
	
	transmission_arg = (dist-distance_in_layer)/avisibility;


	if (visibility < avisibility)
		{
		transmission_arg = transmission_arg + (distance_in_layer/visibility);
		eqColorFactor = 1.0 - 0.1 * delta_zv/visibility - (1.0 -effective_scattering);
		}
	else 
		{
		transmission_arg = transmission_arg + (distance_in_layer/avisibility);
		eqColorFactor = 1.0 - 0.1 * delta_zv/avisibility - (1.0 -effective_scattering);
		}
	transmission =  fog_func(transmission_arg, alt);
	if (eqColorFactor < 0.2) eqColorFactor = 0.2;
	}
else
	{
	eqColorFactor = 1.0;
	transmission = 1.0;
	}

/// END fog amount

/// BEGIN fog color

	vec3 hazeColor;

	if (transmission<  1.0)
	{

	hazeColor.b = light_func(fog_lightArg-0.5, 1.330e-05, 0.264, 2.527, 1.08e-05, 1.0);
	hazeColor.g = light_func(fog_lightArg-0.5, 3.931e-06, 0.264, 3.827, 7.93e-06, 1.0);
	hazeColor.r = light_func(fog_lightArg-0.5, 8.305e-06, 0.161, 3.827, 3.04e-05, 1.0);

	if (fog_lightArg < 10.0)
		{
		intensity = length(hazeColor);
		float mie_magnitude = 0.5 * smoothstep(350000.0, 150000.0, terminator-sqrt(2.0 * EarthRadius * terrain_alt));
		hazeColor = intensity * ((1.0 - mie_magnitude) + mie_magnitude * mie_angle) * normalize(mix(hazeColor,  vec3 (0.5, 0.58, 0.65), mie_magnitude * (0.5 - 0.5 * mie_angle)) ); 
		}

	intensity = length(hazeColor);
	hazeColor = intensity * normalize (mix(hazeColor, intensity * vec3 (1.0,1.0,1.0), 0.7* smoothstep(5000.0, 50000.0, alt)));

	hazeColor.r = hazeColor.r * 0.83;
	hazeColor.g = hazeColor.g * 0.9; 

	float fade_out = max(0.65 - 0.3 *overcast, 0.45);
	intensity = length(hazeColor);
	hazeColor = intensity * normalize(mix(hazeColor,  1.5* shadedFogColor, 1.0 -smoothstep(0.25, fade_out,fog_earthShade) )); 
	hazeColor = intensity * normalize(mix(hazeColor,  shadedFogColor, (1.0-smoothstep(0.5,0.9,eqColorFactor)))); 
	
	float shadow = mix( min(1.0 + dot(VNormal,gl_LightSource[0].position.xyz),1.0), 1.0, 1.0-smoothstep(0.1, 0.4, transmission));
	hazeColor = mix(shadow * hazeColor, hazeColor, 0.3 + 0.7* smoothstep(250000.0, 400000.0, terminator));
	}
	else
	{
	hazeColor = vec3 (1.0, 1.0, 1.0);
	}

	
/// END fog color
    fragColor = clamp(fragColor, 0.0, 1.0);
	//fragColor = fragColor * smoothstep(-0.05, 0.05, ct);
	fragColor.rgb = mix(eqColorFactor * hazeColor * fog_earthShade, fragColor.rgb,transmission);
	gl_FragColor = fragColor;
}