Environment Mapped Reflections

A Shader for applying environment mapped reflections on a reflective object.

//////////////////////////////////
//  Environment Mapped Reflections
//
//////////////////////////////////
 
float4x4 World;
float4x4 WorldInvTrans;
float4x4 WorldViewProj;
float3 EyePos;
 
texture EnvMap;
sampler EnvTex = sampler_state
{
	Texture = <EnvMap>;
	MinFilter = Anisotropic;
	MagFilter = LINEAR;
	MipFilter = LINEAR;
	MaxAnisotropy = 8;
	AddressU  = WRAP;
        AddressV  = WRAP;
};
 
struct VertexShaderInput
{
    float4 Position : POSITION0;
    float4 Normal	: NORMAL0;
};
 
struct VertexShaderOutput
{
    float4 PosH		: POSITION0;
    float3 PosW		: TEXCOORD0;
    float3 NormalW	: TEXCOORD1;
};
 
VertexShaderOutput VertexShaderFunction(VertexShaderInput input)
{
    VertexShaderOutput output;
 
    output.PosH = mul(input.Position, WorldViewProj);
 
    output.PosW = mul(input.Position, World);
 
    output.NormalW = mul(input.Normal, WorldInvTrans);
 
    return output;
}
 
float4 PixelShaderFunction(VertexShaderOutput input) : COLOR0
{
    input.NormalW = normalize(input.NormalW);
 
    //compute the vector from the camera eye position to the world space pixel position.
    float3 fromEyeW = normalize(input.PosW - EyePos);
 
    //find the relflected ray by reflecting the fromEyeW vector across the normal
    float3 reflectedRay = reflect(fromEyeW, input.NormalW);
 
    //finally, index the cube map with the 3d reflected ray vector.
    return texCUBE(EnvTex, reflectedRay);
}
 
technique EnvironmentMap
{
    pass Pass1
    {		
        VertexShader = compile vs_2_0 VertexShaderFunction();
        PixelShader = compile ps_2_0 PixelShaderFunction();
    }
}