HLSL Beckman Normal Distribution не получается.

struct VertexInput {
    float4 vertex : POSITION;       //local vertex position
    float3 normal : NORMAL;         //normal direction
    float4 tangent : TANGENT;       //tangent direction    
    float2 texcoord0 : TEXCOORD0;   //uv coordinates
    float2 texcoord1 : TEXCOORD1;   //lightmap uv coordinates
};

struct VertexOutput {
    float4 pos : SV_POSITION;              //screen clip space position and depth
    float2 uv0 : TEXCOORD0;                //uv coordinates
    float2 uv1 : TEXCOORD1;                //lightmap uv coordinates

//below we create our own variables with the texcoord semantic. 
    float3 normalDir : TEXCOORD3;          //normal direction   
    float3 posWorld : TEXCOORD4;          //normal direction   
    float3 tangentDir : TEXCOORD5;
    float3 bitangentDir : TEXCOORD6;
    LIGHTING_COORDS(7,8)                   //this initializes the unity lighting and shadow
    UNITY_FOG_COORDS(9)                    //this initializes the unity fog
};

VertexOutput vert (VertexInput v) {
     VertexOutput o = (VertexOutput)0;           
     o.uv0 = v.texcoord0;
     o.uv1 = v.texcoord1;
     o.normalDir = UnityObjectToWorldNormal(v.normal);
     o.tangentDir = normalize( mul( _Object2World, float4( v.tangent.xyz, 0.0 ) ).xyz );
     o.bitangentDir = normalize(cross(o.normalDir, o.tangentDir) * v.tangent.w);
     o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
     o.posWorld = mul(_Object2World, v.vertex);
     UNITY_TRANSFER_FOG(o,o.pos);
     TRANSFER_VERTEX_TO_FRAGMENT(o)
     return o;
}