Add existing to tracked

node_modules/@cesium/engine/Source/Shaders/ComputeIrradianceFS.glsl

@@ -0,0 +1,103 @@
+uniform samplerCube u_radianceMap;
+
+in vec2 v_textureCoordinates;
+
+
+const float twoSqrtPi = 2.0 * sqrt(czm_pi);
+
+// Coutesy of https://www.ppsloan.org/publications/StupidSH36.pdf
+float computeShBasis(int index, vec3 s) {
+    if (index == 0) { // l = 0, m = 0
+        return 1.0 / twoSqrtPi;
+    }
+    
+    if (index == 1) { // l = 1, m = -1
+        return -sqrt(3.0) * s.y / twoSqrtPi;
+    }
+
+    if (index == 2) { // l = 1, m = 0
+        return sqrt(3.0) * s.z / twoSqrtPi;
+    }
+
+    if (index == 3) { // l = 1, m = 1
+        return -sqrt(3.0) * s.x / twoSqrtPi;
+    }
+
+    if (index == 4) { // l = 2, m = -2
+        return sqrt(15.0) * s.y * s.x / twoSqrtPi;
+    }
+
+    if (index == 5) { // l = 2, m = -1
+        return -sqrt(15.0) * s.y * s.z / twoSqrtPi;
+    }
+
+    if (index == 6) { // l = 2, m = 0
+        return sqrt(5.0) * (3.0 * s.z * s.z - 1.0) / 2.0 / twoSqrtPi;
+    }
+
+    if (index == 7) { // l = 2, m = 1
+        return -sqrt(15.0) * s.x * s.z / twoSqrtPi;
+    }
+
+    if (index == 8) { // l = 2, m = 2
+        return sqrt(15.0) * (s.x * s.x - s.y * s.y) / 2.0 / twoSqrtPi;
+    }
+
+    return 0.0;
+}
+
+float vdcRadicalInverse(int i)
+{
+    float r;
+    float base = 2.0;
+    float value = 0.0;
+    float invBase = 1.0 / base;
+    float invBi = invBase;
+    for (int x = 0; x < 100; x++)
+    {
+        if (i <= 0)
+        {
+            break;
+        }
+        r = mod(float(i), base);
+        value += r * invBi;
+        invBi *= invBase;
+        i = int(float(i) * invBase);
+    }
+    return value;
+}
+
+vec2 hammersley2D(int i, int N)
+{
+    return vec2(float(i) / float(N), vdcRadicalInverse(i));
+}
+
+// Sample count is relatively low for the sake of performance, but should still be enough to capture directionality needed for third-order harmonics
+const int samples = 256; 
+const float solidAngle = 1.0 / float(samples);
+
+void main() {
+    // Get the current coefficient based on the uv
+   vec2 uv = v_textureCoordinates.xy * 3.0;
+   int coefficientIndex = int(floor(uv.y) * 3.0 + floor(uv.x));
+
+    for (int i = 0; i < samples; ++i) {
+        vec2 xi = hammersley2D(i, samples);
+        float phi = czm_twoPi * xi.x;
+        float cosTheta = 1.0 - 2.0 * sqrt(1.0 - xi.y * xi.y);
+        float sinTheta = sqrt(1.0 - cosTheta * cosTheta);
+        vec3 direction = normalize(vec3(sinTheta * cos(phi), cosTheta, sinTheta * sin(phi)));
+
+        // Generate the spherical harmonics basis from the direction
+        float Ylm = computeShBasis(coefficientIndex, direction);
+
+        vec3 lookupDirection = -direction.xyz;
+        lookupDirection.z = -lookupDirection.z;
+
+        vec4 color = czm_textureCube(u_radianceMap, lookupDirection, 0.0);
+
+        // Use the relevant function for this coefficient
+        out_FragColor += Ylm * color * solidAngle * sinTheta;
+    }
+    
+}