Неполадки с точечным светом/нормалями

Assimp::Importer importer;
    const aiScene* spherescene = importer.ReadFile("sphere.obj", 
        aiProcess_CalcTangentSpace |
        aiProcess_Triangulate |
        aiProcess_JoinIdenticalVertices |
        aiProcess_MakeLeftHanded |
        aiProcess_FlipUVs |
        aiProcess_FlipWindingOrder |
        aiProcess_FindInvalidData
        );
 
    buffers = new Buffers[1];
    buffers[0].vertexcount = spherescene->mMeshes[0]->mNumVertices;
    buffers[0].indexcount = (spherescene->mMeshes[0]->mNumFaces * spherescene->mMeshes[0]->mFaces->mNumIndices) * 2;
    buffers[0].vertices = new Vertex[buffers[0].vertexcount];
    
    for (int i = 0; i < buffers[0].vertexcount; i++)
    {
        buffers[0].vertices[i].Pos = XMFLOAT3(spherescene->mMeshes[0]->mVertices[i].x, spherescene->mMeshes[0]->mVertices[i].y, spherescene->mMeshes[0]->mVertices[i].z);
        buffers[0].vertices[i].Tex = XMFLOAT2(spherescene->mMeshes[0]->mTextureCoords[0][i].x, spherescene->mMeshes[0]->mTextureCoords[0][i].y);
        buffers[0].vertices[i].Norm = XMFLOAT3(spherescene->mMeshes[0]->mNormals[i].x, spherescene->mMeshes[0]->mNormals[i].y, spherescene->mMeshes[0]->mNormals[i].z);
    }
 
    buffers[0].indices = new WORD[buffers[0].indexcount];
    int j = 0;
    for (int i = 0; i < spherescene->mMeshes[0]->mNumFaces; i++)
    {
        buffers[0].indices[j] = spherescene->mMeshes[0]->mFaces[i].mIndices[0];
        buffers[0].indices[j+1] = spherescene->mMeshes[0]->mFaces[i].mIndices[2];
        buffers[0].indices[j+2] = spherescene->mMeshes[0]->mFaces[i].mIndices[1];
 
        buffers[0].indices[j+3] = spherescene->mMeshes[0]->mFaces[i].mIndices[0];
        buffers[0].indices[j+4] = spherescene->mMeshes[0]->mFaces[i].mIndices[1];
        buffers[0].indices[j+5] = spherescene->mMeshes[0]->mFaces[i].mIndices[2];
        j += 6;
    }

//--------------------------------------------------------------------------------------
// Вершинные шейдеры
//--------------------------------------------------------------------------------------
PS_INPUT VS( VS_INPUT input)
{   
    PS_INPUT output = (PS_INPUT)0;
    output.Pos = mul( input.Pos, World );
    output.worldPos = output.Pos;
    output.Pos = mul( output.Pos, View );
    output.Pos = mul( output.Pos, Projection );
    output.Norm = mul(input.Norm, World);
//  float PI = 3.141592654f;
    output.Tex = input.Tex;
    return output;
}
//--------------------------------------------------------------------------------------
// Пиксельные шейдеры
//--------------------------------------------------------------------------------------
float4 PS( PS_INPUT input) : SV_Target
{
    float cutoff = 0.005f;
    float lightRadius = 100000.0f;
    float4 lightColor = float4(1.0f, 1.0f, 1.0f, 1.0f);
    float3 lightCenter = float3(400.0f, 0.0f, 0.0f);
    float4 diffuse = txDiffuse.Sample(samLinear, input.Tex);
    float r = lightRadius;
    float3 L = lightCenter - input.worldPos;
    float distance = length(L);
    float d = max(distance - r, 0);
    L /= distance;
    float denom = d/r + 1;
    float attenuation = 1 / (denom*denom);
    attenuation = (attenuation - cutoff) / (1 - cutoff);
    attenuation = max(attenuation, 0);
     
    float dt = max(dot(L, input.Norm), 0);
    return diffuse * lightColor * dt * attenuation;
}

//--------------------------------------------------------------------------------------
// Форматы данных
//--------------------------------------------------------------------------------------
struct VS_INPUT
{
    float4 Pos : POSITION;
    float2 Tex : TEXCOORD0;  
    float3 Norm : NORMAL;
};
 
struct PS_INPUT
{
    float4 Pos : SV_POSITION;
    float4 worldPos : POSITION;
    float2 Tex : TEXCOORD0;  
    float3 Norm : NORMAL;
};

D3DXVECTOR3 a, b, c, sba, sca, norm; //a, b, c - вершины треугольника norm - нормаль
D3DXVec3Subtract(&sba, &b, &a); //вектор ab
D3DXVec3Subtract(&sca, &c, &a); //вектор ac
D3DXVec3Cross(&norm, &sba, &sca); //векторное произведение
D3DXVec3Normalize(&norm, &norm);

D3DXVECTOR3 a, c, norm; //a - точка на сфере, c - центр сферы, norm - нормаль
D3DXVec3Subtract(&norm, &a, &c); //вектор ca
D3DXVec3Normalize(&norm, &norm);