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diff --git a/indra/newview/app_settings/shaders/class1/interface/irradianceGenF.glsl b/indra/newview/app_settings/shaders/class1/interface/irradianceGenF.glsl
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+/** 
+ * @file irradianceGenF.glsl
+ *
+ * $LicenseInfo:firstyear=2022&license=viewerlgpl$
+ * Second Life Viewer Source Code
+ * Copyright (C) 2022, Linden Research, Inc.
+ * 
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation;
+ * version 2.1 of the License only.
+ * 
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ * 
+ * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
+ * $/LicenseInfo$
+ */
+ 
+
+/*[EXTRA_CODE_HERE]*/
+
+
+#ifdef DEFINE_GL_FRAGCOLOR
+out vec4 frag_color;
+#else
+#define frag_color gl_FragColor
+#endif
+
+uniform samplerCubeArray   reflectionProbes;
+uniform int sourceIdx;
+
+VARYING vec3 vary_dir;
+
+
+// Code below is derived from the Khronos GLTF Sample viewer:
+// https://github.com/KhronosGroup/glTF-Sample-Viewer/blob/master/source/shaders/ibl_filtering.frag
+
+
+#define MATH_PI 3.1415926535897932384626433832795
+
+float u_roughness = 1.0;
+int u_sampleCount = 16;
+float u_lodBias = 2.0;
+int u_width = 64;
+
+// Hammersley Points on the Hemisphere
+// CC BY 3.0 (Holger Dammertz)
+// http://holger.dammertz.org/stuff/notes_HammersleyOnHemisphere.html
+// with adapted interface
+float radicalInverse_VdC(uint bits)
+{
+    bits = (bits << 16u) | (bits >> 16u);
+    bits = ((bits & 0x55555555u) << 1u) | ((bits & 0xAAAAAAAAu) >> 1u);
+    bits = ((bits & 0x33333333u) << 2u) | ((bits & 0xCCCCCCCCu) >> 2u);
+    bits = ((bits & 0x0F0F0F0Fu) << 4u) | ((bits & 0xF0F0F0F0u) >> 4u);
+    bits = ((bits & 0x00FF00FFu) << 8u) | ((bits & 0xFF00FF00u) >> 8u);
+    return float(bits) * 2.3283064365386963e-10; // / 0x100000000
+}
+
+// hammersley2d describes a sequence of points in the 2d unit square [0,1)^2
+// that can be used for quasi Monte Carlo integration
+vec2 hammersley2d(int i, int N) {
+    return vec2(float(i)/float(N), radicalInverse_VdC(uint(i)));
+}
+
+// Hemisphere Sample
+
+// TBN generates a tangent bitangent normal coordinate frame from the normal
+// (the normal must be normalized)
+mat3 generateTBN(vec3 normal)
+{
+    vec3 bitangent = vec3(0.0, 1.0, 0.0);
+
+    float NdotUp = dot(normal, vec3(0.0, 1.0, 0.0));
+    float epsilon = 0.0000001;
+    /*if (1.0 - abs(NdotUp) <= epsilon)
+    {
+        // Sampling +Y or -Y, so we need a more robust bitangent.
+        if (NdotUp > 0.0)
+        {
+            bitangent = vec3(0.0, 0.0, 1.0);
+        }
+        else
+        {
+            bitangent = vec3(0.0, 0.0, -1.0);
+        }
+    }*/
+
+    vec3 tangent = normalize(cross(bitangent, normal));
+    bitangent = cross(normal, tangent);
+
+    return mat3(tangent, bitangent, normal);
+}
+
+struct MicrofacetDistributionSample
+{
+    float pdf;
+    float cosTheta;
+    float sinTheta;
+    float phi;
+};
+
+MicrofacetDistributionSample Lambertian(vec2 xi, float roughness)
+{
+    MicrofacetDistributionSample lambertian;
+
+    // Cosine weighted hemisphere sampling
+    // http://www.pbr-book.org/3ed-2018/Monte_Carlo_Integration/2D_Sampling_with_Multidimensional_Transformations.html#Cosine-WeightedHemisphereSampling
+    lambertian.cosTheta = sqrt(1.0 - xi.y);
+    lambertian.sinTheta = sqrt(xi.y); // equivalent to `sqrt(1.0 - cosTheta*cosTheta)`;
+    lambertian.phi = 2.0 * MATH_PI * xi.x;
+
+    lambertian.pdf = lambertian.cosTheta / MATH_PI; // evaluation for solid angle, therefore drop the sinTheta
+
+    return lambertian;
+}
+
+
+// getImportanceSample returns an importance sample direction with pdf in the .w component
+vec4 getImportanceSample(int sampleIndex, vec3 N, float roughness)
+{
+    // generate a quasi monte carlo point in the unit square [0.1)^2
+    vec2 xi = hammersley2d(sampleIndex, u_sampleCount);
+
+    MicrofacetDistributionSample importanceSample;
+
+    // generate the points on the hemisphere with a fitting mapping for
+    // the distribution (e.g. lambertian uses a cosine importance)
+    importanceSample = Lambertian(xi, roughness);
+    
+    // transform the hemisphere sample to the normal coordinate frame
+    // i.e. rotate the hemisphere to the normal direction
+    vec3 localSpaceDirection = normalize(vec3(
+        importanceSample.sinTheta * cos(importanceSample.phi), 
+        importanceSample.sinTheta * sin(importanceSample.phi), 
+        importanceSample.cosTheta
+    ));
+    mat3 TBN = generateTBN(N);
+    vec3 direction = TBN * localSpaceDirection;
+
+    return vec4(direction, importanceSample.pdf);
+}
+
+// Mipmap Filtered Samples (GPU Gems 3, 20.4)
+// https://developer.nvidia.com/gpugems/gpugems3/part-iii-rendering/chapter-20-gpu-based-importance-sampling
+// https://cgg.mff.cuni.cz/~jaroslav/papers/2007-sketch-fis/Final_sap_0073.pdf
+float computeLod(float pdf)
+{
+    // // Solid angle of current sample -- bigger for less likely samples
+    // float omegaS = 1.0 / (float(u_sampleCount) * pdf);
+    // // Solid angle of texel
+    // // note: the factor of 4.0 * MATH_PI 
+    // float omegaP = 4.0 * MATH_PI / (6.0 * float(u_width) * float(u_width));
+    // // Mip level is determined by the ratio of our sample's solid angle to a texel's solid angle 
+    // // note that 0.5 * log2 is equivalent to log4
+    // float lod = 0.5 * log2(omegaS / omegaP);
+
+    // babylon introduces a factor of K (=4) to the solid angle ratio
+    // this helps to avoid undersampling the environment map
+    // this does not appear in the original formulation by Jaroslav Krivanek and Mark Colbert
+    // log4(4) == 1
+    // lod += 1.0;
+
+    // We achieved good results by using the original formulation from Krivanek & Colbert adapted to cubemaps
+
+    // https://cgg.mff.cuni.cz/~jaroslav/papers/2007-sketch-fis/Final_sap_0073.pdf
+    float lod = 0.5 * log2( 6.0 * float(u_width) * float(u_width) / (float(u_sampleCount) * pdf));
+
+
+    return lod;
+}
+
+vec4 filterColor(vec3 N)
+{
+    //return  textureLod(uCubeMap, N, 3.0).rgb;
+    vec4 color = vec4(0.f);
+    float weight = 0.0f;
+
+    for(int i = 0; i < u_sampleCount; ++i)
+    {
+        vec4 importanceSample = getImportanceSample(i, N, 1.0);
+
+        vec3 H = vec3(importanceSample.xyz);
+        float pdf = importanceSample.w;
+
+        // mipmap filtered samples (GPU Gems 3, 20.4)
+        float lod = computeLod(pdf);
+
+        // apply the bias to the lod
+        lod += u_lodBias;
+
+        lod = clamp(lod, 0, 6);
+        // sample lambertian at a lower resolution to avoid fireflies
+        vec4 lambertian = textureLod(reflectionProbes, vec4(H, sourceIdx), lod);
+
+        color += lambertian;
+    }
+
+    if(weight != 0.0f)
+    {
+        color /= weight;
+    }
+    else
+    {
+        color /= float(u_sampleCount);
+    }
+
+    return color;
+}
+
+// entry point
+void main()
+{
+    vec4 color = vec4(0);
+
+    color = filterColor(vary_dir);
+    
+    frag_color = color;
+}
+