HRESULT DeferredPointLight(D3DXVECTOR3 vLightPosition, D3DXVECTOR3 vColour, float fLightRadius, float fLightIntensity, LPDIRECT3DSURFACE9 pBackBuffer)
{
    UINT uiPass, uiPassCount;
    //HRESULT hr;

    V_RETURN(g_pd3dDevice->SetRenderTarget(0, g_pSurfaceLightMap));

    V_RETURN(g_pPointLight->SetTechnique("PointLight"));
    V_RETURN(g_pPointLight->SetTexture("colorMap", g_pColourRT));
    V_RETURN(g_pPointLight->SetTexture("normalMap", g_pNormalRT));
    V_RETURN(g_pPointLight->SetTexture("depthMap", g_pDepthRT));

    // compute the light world matrix
        // scale according to light radius, and translate it to light position
    D3DXMATRIX mSphereWorldMatrix;
    D3DXMATRIX mScaleMatrix;
    D3DXMATRIX mTranslationMatrix;

    D3DXMatrixScaling(&mScaleMatrix, fLightRadius, fLightRadius, fLightRadius);
    D3DXMatrixTranslation(&mTranslationMatrix, vLightPosition.x, vLightPosition.y, vLightPosition.z);
    mSphereWorldMatrix = mScaleMatrix * mTranslationMatrix;

    D3DXMATRIX mViewProj = D3DXMATRIX(g_Camera.GetViewMatrix() * g_Camera.GetProjectionMatrix());
    D3DXMATRIX mInverseViewProj;
    D3DXMatrixInverse(&mInverseViewProj, NULL, &mViewProj);

    D3DXVECTOR3 vViewPosition = g_Camera.GetEyeVector();

    V_RETURN(g_pPointLight->SetValue("World", mSphereWorldMatrix, sizeof(mSphereWorldMatrix)));
    V_RETURN(g_pPointLight->SetValue("View", g_Camera.GetViewMatrix(), sizeof(g_Camera.GetViewMatrix())));
    V_RETURN(g_pPointLight->SetValue("Projection", g_Camera.GetProjectionMatrix(), sizeof(g_Camera.GetProjectionMatrix())));
    V_RETURN(g_pPointLight->SetValue("lightPosition", vLightPosition, sizeof(vLightPosition)));
    V_RETURN(g_pPointLight->SetValue("Color", vColour, sizeof(vColour)));
    V_RETURN(g_pPointLight->SetFloat("lightRadius", fLightRadius));
    V_RETURN(g_pPointLight->SetFloat("lightIntensity", fLightIntensity));
    V_RETURN(g_pPointLight->SetValue("cameraPosition", vViewPosition, sizeof(vViewPosition)));
    V_RETURN(g_pPointLight->SetValue("InvertViewProjection", mInverseViewProj, sizeof(mInverseViewProj)));

    float fCameraToCentre;
    float xDistance;
    float yDistance;
    float zDistance;

    xDistance = pow(vViewPosition.x - vLightPosition.x, 2.0f);
    yDistance = pow(vViewPosition.y - vLightPosition.y, 2.0f);
    zDistance = pow(vViewPosition.z - vLightPosition.z, 2.0f);

    fCameraToCentre = pow(xDistance + yDistance + zDistance, 0.5f);

    if(fCameraToCentre < fLightRadius)
    {
        V_RETURN(g_pd3dDevice->SetRenderState(D3DRS_CULLMODE, D3DCULL_CW));
    }

    else
    {
        V_RETURN(g_pd3dDevice->SetRenderState(D3DRS_CULLMODE, D3DCULL_CCW));
    }

    V_RETURN(g_pd3dDevice->SetVertexDeclaration(g_pVertexDecl));

    V_RETURN(g_pPointLight->Begin(&uiPassCount, 0));
    for(uiPass = 0; uiPass < uiPassCount; uiPass++)
    {
        V_RETURN(g_pPointLight->BeginPass(uiPass));

        // Draw a fullscreen quad to sample the RT
        DrawFullScreenQuad(0.0f, 0.0f, 1.0f, 1.0f);

        V_RETURN(g_pPointLight->EndPass());
    }
    V_RETURN(g_pPointLight->End());

    V_RETURN(g_pd3dDevice->SetRenderState(D3DRS_CULLMODE, D3DCULL_CCW));

    return S_OK;
}