uniform extern float4x4 gWVP;
uniform extern texture  gEnvMap;
uniform extern float3  gEyePosW;

//FOG INPUTS WILL MAKE IT SO WE SET THE COLOUR
static float3 gFogColor = {1.5f, 0.5f, 0.5f};
static float  gFogStart = 1.0f;
static float  gFogRange = 20.0f;


sampler EnvMapS = sampler_state
{
    Texture   = <gEnvMap>;
    MinFilter = LINEAR; 
    MagFilter = LINEAR;
    MipFilter = LINEAR;
    AddressU  = WRAP;
    AddressV  = WRAP;
};


void SkyVS(float3 posL : POSITION0, 
           out float4 oPosH : POSITION0, 
           out float3 oEnvTex : TEXCOORD0,
	   out float  fogLerpParam : TEXCOORD1)
{
	// Set z = w so that z/w = 1 (i.e., skydome always on far plane).
    	oPosH = mul(float4(posL, 1.0f), gWVP).xyww; 
    
    	// Use skymesh vertex position, in local space, as index into cubemap. 
    	oEnvTex = posL;

	// Compute vertex distance from camera in world space for fog calculation.
	float dist = distance(posL, gEyePosW);
	fogLerpParam = saturate((dist - gFogStart) / gFogRange);

}

float4 SkyPS(float3 envTex : TEXCOORD0,
		float fogLerpParam : TEXCOORD2) : COLOR
{
HERE IS THE AREA
// Add fog.
    float4 tc = texCUBE(EnvMapS, envTex);
	
	
    float3 final = lerp(tc, gFogColor, fogLerpParam);

    float4 ft = float4(final, 1.0f);

    return ft;

    //return texCUBE(EnvMapS, envTex);
}

technique SkyTech
{
    pass P0
    {
        vertexShader = compile vs_2_0 SkyVS();
        pixelShader  = compile ps_2_0 SkyPS();
		CullMode = None;
		ZFunc = Always; // Always write sky to depth buffer
		StencilEnable = true;
		StencilFunc   = Always;
		StencilPass   = Replace;
		StencilRef    = 0; // clear to zero
    }
}