diff --git a/libraries/pbrlib/genglsl/lib/mx_microfacet_specular.glsl b/libraries/pbrlib/genglsl/lib/mx_microfacet_specular.glsl
index 53b55e259a..904c9978ec 100644
--- a/libraries/pbrlib/genglsl/lib/mx_microfacet_specular.glsl
+++ b/libraries/pbrlib/genglsl/lib/mx_microfacet_specular.glsl
@@ -218,28 +218,21 @@ vec3 mx_fresnel_hoffman_schlick(float cosTheta, FresnelData fd)
 // https://seblagarde.wordpress.com/2013/04/29/memo-on-fresnel-equations/
 float mx_fresnel_dielectric(float cosTheta, float ior)
 {
-    if (cosTheta < 0.0)
+    float c = cosTheta;
+    float g2 = ior*ior + c*c - 1.0;
+    if (g2 < 0.0)
     {
+        // Total internal reflection
         return 1.0;
     }
 
-    float g = ior*ior + cosTheta*cosTheta - 1.0;
-
-    // Check for total internal reflection
-    if (g < 0.0)
-    {
-        return 1.0;
-    }
-
-    g = sqrt(g);
-    float gmc = g - cosTheta;
-    float gpc = g + cosTheta;
-    float x = gmc / gpc;
-    float y = (gpc * cosTheta - 1.0) / (gmc * cosTheta + 1.0);
-    return 0.5 * x * x * (1.0 + y * y);
+    float g = sqrt(g2);
+    return 0.5 * mx_square((g - c) / (g + c)) *
+                (1.0 + mx_square(((g + c) * c - 1.0) / ((g - c) * c + 1.0)));
 }
 
-void mx_fresnel_dielectric_polarized(float cosTheta, float ior, out float Rp, out float Rs)
+// https://seblagarde.wordpress.com/2013/04/29/memo-on-fresnel-equations/
+vec2 mx_fresnel_dielectric_polarized(float cosTheta, float ior)
 {
     float cosTheta2 = mx_square(clamp(cosTheta, 0.0, 1.0));
     float sinTheta2 = 1.0 - cosTheta2;
@@ -247,13 +240,16 @@ void mx_fresnel_dielectric_polarized(float cosTheta, float ior, out float Rp, ou
     float t0 = max(ior * ior - sinTheta2, 0.0);
     float t1 = t0 + cosTheta2;
     float t2 = 2.0 * sqrt(t0) * cosTheta;
-    Rs = (t1 - t2) / (t1 + t2);
+    float Rs = (t1 - t2) / (t1 + t2);
 
     float t3 = cosTheta2 * t0 + sinTheta2 * sinTheta2;
     float t4 = t2 * sinTheta2;
-    Rp = Rs * (t3 - t4) / (t3 + t4);
+    float Rp = Rs * (t3 - t4) / (t3 + t4);
+
+    return vec2(Rp, Rs);
 }
 
+// https://seblagarde.wordpress.com/2013/04/29/memo-on-fresnel-equations/
 void mx_fresnel_conductor_polarized(float cosTheta, vec3 n, vec3 k, out vec3 Rp, out vec3 Rs)
 {
     float cosTheta2 = mx_square(clamp(cosTheta, 0.0, 1.0));
@@ -280,34 +276,9 @@ vec3 mx_fresnel_conductor(float cosTheta, vec3 n, vec3 k)
     return 0.5 * (Rp  + Rs);
 }
 
-// Phase shift due to a dielectric material
-void mx_fresnel_dielectric_phase_polarized(float cosTheta, float eta1, float eta2, out float phiP, out float phiS)
-{
-    float cosB = cos(atan(eta2 / eta1)); // Brewster's angle
-    if (eta2 > eta1)
-    {
-        phiP = cosTheta < cosB ? M_PI : 0.0f;
-        phiS = 0.0f;
-    }
-    else
-    {
-        phiP = cosTheta < cosB ? 0.0f : M_PI;
-        phiS = M_PI;
-    }
-}
-
-// Phase shift due to a conducting material
+// https://belcour.github.io/blog/research/publication/2017/05/01/brdf-thin-film.html
 void mx_fresnel_conductor_phase_polarized(float cosTheta, float eta1, vec3 eta2, vec3 kappa2, out vec3 phiP, out vec3 phiS)
 {
-    if (dot(kappa2, kappa2) == 0.0 && eta2.x == eta2.y && eta2.y == eta2.z)
-    {
-        // Use dielectric formula to increase performance
-        float phiPx, phiSx;
-        mx_fresnel_dielectric_phase_polarized(cosTheta, eta1, eta2.x, phiPx, phiSx);
-        phiP = vec3(phiPx, phiPx, phiPx);
-        phiS = vec3(phiSx, phiSx, phiSx);
-        return;
-    }
     vec3 k2 = kappa2 / eta2;
     vec3 sinThetaSqr = vec3(1.0) - cosTheta * cosTheta;
     vec3 A = eta2*eta2*(vec3(1.0)-k2*k2) - eta1*eta1*sinThetaSqr;
@@ -320,7 +291,7 @@ void mx_fresnel_conductor_phase_polarized(float cosTheta, float eta1, vec3 eta2,
                 mx_square(eta2*eta2*(vec3(1.0)+k2*k2)*cosTheta) - eta1*eta1*(U*U+V*V));
 }
 
-// Evaluation XYZ sensitivity curves in Fourier space
+// https://belcour.github.io/blog/research/publication/2017/05/01/brdf-thin-film.html
 vec3 mx_eval_sensitivity(float opd, vec3 shift)
 {
     // Use Gaussian fits, given by 3 parameters: val, pos and var
@@ -340,57 +311,39 @@ vec3 mx_fresnel_airy(float cosTheta, FresnelData fd)
     // XYZ to CIE 1931 RGB color space (using neutral E illuminant)
     const mat3 XYZ_TO_RGB = mat3(2.3706743, -0.5138850, 0.0052982, -0.9000405, 1.4253036, -0.0146949, -0.4706338, 0.0885814, 1.0093968);
 
-    // Convert nm -> m
-    float d = fd.tf_thickness * 1.0e-9;
-
     // Assume vacuum on the outside
     float eta1 = 1.0;
     float eta2 = max(fd.tf_ior, eta1);
     vec3 eta3 = (fd.model == FRESNEL_MODEL_SCHLICK) ? mx_f0_to_ior(fd.F0) : fd.ior;
     vec3 kappa3 = (fd.model == FRESNEL_MODEL_SCHLICK) ? vec3(0.0) : fd.extinction;
+    float cosThetaT = sqrt(1.0 - (1.0 - mx_square(cosTheta)) * mx_square(eta1 / eta2));
 
-    // Compute the Spectral versions of the Fresnel reflectance and
-    // transmitance for each interface.
-    float R12p, T121p, R12s, T121s;
+    // First interface
+    vec2 R12 = mx_fresnel_dielectric_polarized(cosTheta, eta2 / eta1);
+    if (cosThetaT <= 0.0)
+    {
+        // Total internal reflection
+        R12 = vec2(1.0);
+    }
+    vec2 T121 = vec2(1.0) - R12;
+
+    // Second interface
     vec3 R23p, R23s;
-    
-    // Reflected and transmitted parts in the thin film
-    mx_fresnel_dielectric_polarized(cosTheta, eta2 / eta1, R12p, R12s);
-
-    // Reflected part by the base
-    float scale = eta1 / eta2;
-    float cosThetaTSqr = 1.0 - (1.0-cosTheta*cosTheta) * scale*scale;
-    float cosTheta2 = sqrt(cosThetaTSqr);
     if (fd.model == FRESNEL_MODEL_SCHLICK)
     {
-        vec3 f = mx_fresnel_hoffman_schlick(cosTheta2, fd);
+        vec3 f = mx_fresnel_hoffman_schlick(cosThetaT, fd);
         R23p = 0.5 * f;
         R23s = 0.5 * f;
     }
     else
     {
-        mx_fresnel_conductor_polarized(cosTheta2, eta3 / eta2, kappa3 / eta2, R23p, R23s);
-    }
-
-    // Check for total internal reflection
-    if (cosThetaTSqr <= 0.0f)
-    {
-        R12p = 1.0;
-        R12s = 1.0;
+        mx_fresnel_conductor_polarized(cosThetaT, eta3 / eta2, kappa3 / eta2, R23p, R23s);
     }
 
-    // Compute the transmission coefficients
-    T121p = 1.0 - R12p;
-    T121s = 1.0 - R12s;
-
-    // Optical path difference
-    float D = 2.0 * eta2 * d * cosTheta2;
-
-    float phi21p, phi21s;
-    vec3 phi23p, phi23s, r123s, r123p;
-
-    // Evaluate the phase shift
-    mx_fresnel_dielectric_phase_polarized(cosTheta, eta1, eta2, phi21p, phi21s);
+    // Phase shift
+    float cosB = cos(atan(eta2 / eta1));
+    vec2 phi21 = vec2(cosTheta < cosB ? 0.0 : M_PI, M_PI);
+    vec3 phi23p, phi23s;
     if (fd.model == FRESNEL_MODEL_SCHLICK)
     {
         phi23p = vec3((eta3[0] < eta2) ? M_PI : 0.0,
@@ -400,46 +353,46 @@ vec3 mx_fresnel_airy(float cosTheta, FresnelData fd)
     }
     else
     {
-        mx_fresnel_conductor_phase_polarized(cosTheta2, eta2, eta3, kappa3, phi23p, phi23s);
+        mx_fresnel_conductor_phase_polarized(cosThetaT, eta2, eta3, kappa3, phi23p, phi23s);
     }
+    vec3 r123p = max(sqrt(R12.x*R23p), 0.0);
+    vec3 r123s = max(sqrt(R12.y*R23s), 0.0);
 
-    phi21p = M_PI - phi21p;
-    phi21s = M_PI - phi21s;
-
-    r123p = max(vec3(0.0), sqrt(R12p*R23p));
-    r123s = max(vec3(0.0), sqrt(R12s*R23s));
-
-    // Evaluate iridescence term
+    // Iridescence term
     vec3 I = vec3(0.0);
     vec3 Cm, Sm;
 
+    // Optical path difference
+    float distMeters = fd.tf_thickness * 1.0e-9;
+    float opd = 2.0 * eta2 * cosThetaT * distMeters;
+
     // Iridescence term using spectral antialiasing for Parallel polarization
 
     // Reflectance term for m=0 (DC term amplitude)
-    vec3 Rs = (T121p*T121p*R23p) / (vec3(1.0) - R12p*R23p);
-    I += R12p + Rs;
+    vec3 Rs = (mx_square(T121.x) * R23p) / (vec3(1.0) - R12.x*R23p);
+    I += R12.x + Rs;
 
     // Reflectance term for m>0 (pairs of diracs)
-    Cm = Rs - T121p;
+    Cm = Rs - T121.x;
     for (int m=1; m<=2; m++)
     {
         Cm *= r123p;
-        Sm  = 2.0 * mx_eval_sensitivity(float(m)*D, float(m)*(phi23p+vec3(phi21p)));
+        Sm  = 2.0 * mx_eval_sensitivity(float(m) * opd, float(m)*(phi23p+vec3(phi21.x)));
         I  += Cm*Sm;
     }
 
     // Iridescence term using spectral antialiasing for Perpendicular polarization
 
     // Reflectance term for m=0 (DC term amplitude)
-    vec3 Rp = (T121s*T121s*R23s) / (vec3(1.0) - R12s*R23s);
-    I += R12s + Rp;
+    vec3 Rp = (mx_square(T121.y) * R23s) / (vec3(1.0) - R12.y*R23s);
+    I += R12.y + Rp;
 
     // Reflectance term for m>0 (pairs of diracs)
-    Cm = Rp - T121s;
+    Cm = Rp - T121.y;
     for (int m=1; m<=2; m++)
     {
         Cm *= r123s;
-        Sm  = 2.0 * mx_eval_sensitivity(float(m)*D, float(m)*(phi23s+vec3(phi21s)));
+        Sm  = 2.0 * mx_eval_sensitivity(float(m) * opd, float(m)*(phi23s+vec3(phi21.y)));
         I  += Cm*Sm;
     }
 
@@ -447,7 +400,7 @@ vec3 mx_fresnel_airy(float cosTheta, FresnelData fd)
     I *= 0.5;
 
     // Convert back to RGB reflectance
-    I = clamp(XYZ_TO_RGB * I, vec3(0.0), vec3(1.0));
+    I = clamp(XYZ_TO_RGB * I, 0.0, 1.0);
 
     return I;
 }