Add existing to tracked

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

@@ -0,0 +1,70 @@
+precision highp float;
+
+in vec3 v_textureCoordinates;
+
+uniform float u_roughness;
+uniform samplerCube u_radianceTexture;
+uniform vec3 u_faceDirection;
+
+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));
+}
+
+vec3 importanceSampleGGX(vec2 xi, float alphaRoughness, vec3 N)
+{
+    float alphaRoughnessSquared = alphaRoughness * alphaRoughness;
+    float phi = czm_twoPi * xi.x;
+    float cosTheta = sqrt((1.0 - xi.y) / (1.0 + (alphaRoughnessSquared - 1.0) * xi.y));
+    float sinTheta = sqrt(1.0 - cosTheta * cosTheta);
+    vec3 H = vec3(sinTheta * cos(phi), sinTheta * sin(phi), cosTheta);
+    vec3 upVector = abs(N.z) < 0.999 ? vec3(0.0, 0.0, 1.0) : vec3(1.0, 0.0, 0.0);
+    vec3 tangentX = normalize(cross(upVector, N));
+    vec3 tangentY = cross(N, tangentX);
+    return tangentX * H.x + tangentY * H.y + N * H.z;
+}
+
+// Sample count is relatively low for the sake of performance, but should still be enough to prevent artifacting in lower roughnesses
+const int samples = 128;
+
+void main() {
+    vec3 normal = u_faceDirection;
+    vec3 V = normalize(v_textureCoordinates);
+    float roughness = u_roughness;
+
+    vec4 color = vec4(0.0);
+    float weight = 0.0;
+    for (int i = 0; i < samples; ++i) {
+            vec2 xi = hammersley2D(i, samples);
+            vec3 H = importanceSampleGGX(xi, roughness, V);
+            vec3 L = 2.0 * dot(V, H) * H - V; // reflected vector
+
+            float NdotL = max(dot(V, L), 0.0);
+            if (NdotL > 0.0) {
+                color += vec4(czm_textureCube(u_radianceTexture, L).rgb, 1.0) * NdotL;
+                weight += NdotL;
+            }
+        }
+    out_FragColor = color / weight;
+}