GGX microfacet fresnel hack

diff --git a/intern/cycles/kernel/closure/bsdf_microfacet.h b/intern/cycles/kernel/closure/bsdf_microfacet.h
--- a/intern/cycles/kernel/closure/bsdf_microfacet.h
+++ b/intern/cycles/kernel/closure/bsdf_microfacet.h
@@ -342,8 +342,9 @@ ccl_device float3 bsdf_microfacet_ggx_eval_reflect(const ShaderClosure *sc, cons
        float G = G1o * G1i;

        /* eq. 20 */
+       float fresnel = fresnel_dielectric_cos(dot(m,I), 1.45f);
        float common = D * 0.25f / cosNO;
-       float out = G * common;
+       float out = fresnel * G * common;

        /* eq. 2 in distribution of visible normals sampling
         * pm = Dw = G1o * dot(m, I) * D / dot(N, I); */
@@ -501,8 +503,9 @@ ccl_device int bsdf_microfacet_ggx_sample(KernelGlobals *kg, const ShaderClosure
                        }

                        /* see eval function for derivation */
+                       float fresnel = fresnel_dielectric_cos(dot(m,I), 1.45f);
                        float common = (G1o * D) * 0.25f / cosNO;
-                       float out = G1i * common;
+                       float out = fresnel * G1i * common;
                        *pdf = common;

                        *eval = make_float3(out, out, out);