#version 120

varying vec4  rawpos;
varying vec4  ecPosition;
varying vec3  VNormal;
varying vec3  VTangent;
varying vec3  VBinormal;
varying vec3  Normal;
varying vec4  constantColor;
varying float bump;

uniform sampler3D NoiseTex;
uniform sampler2D BaseTex;
uniform sampler2D NormalTex;
uniform float depth_factor;
uniform float quality_level; // From /sim/rendering/quality-level
uniform float snowlevel; // From /sim/rendering/snow-level-m

const float scale = 1.0;
int linear_search_steps = 10;

float ray_intersect(sampler2D reliefMap, vec2 dp, vec2 ds)
{

	float size = 1.0 / float(linear_search_steps);
	float depth = 0.0;
	float best_depth = 1.0;

	for(int i = 0; i < linear_search_steps - 1; ++i)
	{
		depth += size;
		float t = texture2D(reliefMap, dp + ds * depth).a;
		if(best_depth > 0.996)
			if(depth >= t)
				best_depth = depth;
	}
	depth = best_depth;

	const int binary_search_steps = 5;

	for(int i = 0; i < binary_search_steps; ++i)
	{
		size *= 0.5;
		float t = texture2D(reliefMap, dp + ds * depth).a;
		if(depth >= t)
		{
			best_depth = depth;
			depth -= 2.0 * size;
		}
		depth += size;
	}

	return(best_depth);
}

void main (void)
{
	if ( quality_level >= 3.5 ) {
		linear_search_steps = 20;
	}
	vec2 uv, dp, ds;
	vec3 N;
	float d;
	if ( bump > 0.9 && quality_level >= 2.0 )
	{
		vec3 V = normalize(ecPosition.xyz);
		float a = dot(VNormal, -V);
		vec2 s = vec2(dot(V, VTangent), dot(V, VBinormal));
		s *= depth_factor / a;
		ds = s;
		dp = gl_TexCoord[0].st;
		d = ray_intersect(NormalTex, dp, ds);

		uv = dp + ds * d;
		N = texture2D(NormalTex, uv).xyz * 2.0 - 1.0;
	}
	else
	{
		uv = gl_TexCoord[0].st;
		N = vec3(0.0, 0.0, 1.0);
	}

	vec4 noisevec   = texture3D(NoiseTex, (rawpos.xyz)*0.01*scale);
	vec4 nvL   = texture3D(NoiseTex, (rawpos.xyz)*0.00066*scale);

	float fogFactor;
	float fogCoord = ecPosition.z;
	const float LOG2 = 1.442695;
	fogFactor = exp2(-gl_Fog.density * gl_Fog.density * fogCoord * fogCoord * LOG2);
	float biasFactor = fogFactor = clamp(fogFactor, 0.0, 1.0);

	float n=0.06;
	n += nvL[0]*0.4;
	n += nvL[1]*0.6;
	n += nvL[2]*2.0;
	n += nvL[3]*4.0;
	n += noisevec[0]*0.1;
	n += noisevec[1]*0.4;

	n += noisevec[2]*0.8;
	n += noisevec[3]*2.1;
	n = mix(0.6, n, biasFactor);
	// good
	vec4 c1 = texture2D(BaseTex, uv);
	//brown
	//c1 = mix(c1, vec4(n-0.46, n-0.45, n-0.53, 1.0), smoothstep(0.50, 0.55, nvL[2]*6.6));
	//"steep = gray"
	c1 = mix(vec4(n-0.30, n-0.29, n-0.37, 1.0), c1, smoothstep(0.970, 0.990, abs(normalize(Normal).z)+nvL[2]*1.3));
	//"snow"
	c1 = mix(c1, clamp(n+nvL[2]*4.1+vec4(0.1, 0.1, nvL[2]*2.2, 1.0), 0.7, 1.0), smoothstep(snowlevel+300.0, snowlevel+360.0, (rawpos.z)+nvL[1]*3000.0));

	N = normalize(N.x * VTangent + N.y * VBinormal + N.z * VNormal);
	vec3 l = gl_LightSource[0].position.xyz;
	vec3 diffuse = gl_Color.rgb * max(0.0, dot(N, l));
	float shadow_factor = 1.0;

	// Shadow
	if ( quality_level >= 3.0 ) {
		dp += ds * d;
		vec3 sl = normalize( vec3( dot( l, VTangent ), dot( l, VBinormal ), dot( -l, VNormal ) ) );
		ds = sl.xy * depth_factor / sl.z;
		dp -= ds * d;
		float dl = ray_intersect(NormalTex, dp, ds);
		if ( dl < d - 0.05 )
			shadow_factor = dot( constantColor.xyz, vec3( 1.0, 1.0, 1.0 ) ) * 0.25;
	}
	// end shadow

	vec4 ambient_light = constantColor + gl_LightSource[0].diffuse * shadow_factor * vec4(diffuse, 1.0);

	c1 *= ambient_light;
	vec4 finalColor = c1;

	if(gl_Fog.density == 1.0)
		fogFactor=1.0;

	gl_FragColor = mix(gl_Fog.color ,finalColor, fogFactor);
}