Add Chromium-only Blender WebEngine parity work

blender-5.2.0/intern/cycles/util/math_cdf.cpp

@@ -0,0 +1,62 @@
+/* SPDX-FileCopyrightText: 2011-2022 Blender Foundation
+ *
+ * SPDX-License-Identifier: Apache-2.0 */
+
+#include "util/math_cdf.h"
+
+#include <cassert>
+
+#include "util/algorithm.h"
+
+CCL_NAMESPACE_BEGIN
+
+/* Invert pre-calculated CDF function. */
+void util_cdf_invert(const int resolution,
+                     const float from,
+                     const float to,
+                     const vector<float> &cdf,
+                     const bool make_symmetric,
+                     vector<float> &inv_cdf)
+{
+  const int cdf_size = cdf.size();
+  assert(cdf[0] == 0.0f && cdf[cdf_size - 1] == 1.0f);
+
+  const float inv_resolution = 1.0f / (float)resolution;
+  const float range = to - from;
+  inv_cdf.resize(resolution);
+  if (make_symmetric) {
+    const int half_size = (resolution - 1) / 2;
+    for (int i = 0; i <= half_size; i++) {
+      const float x = i / (float)half_size;
+      int index = upper_bound(cdf.begin(), cdf.end(), x) - cdf.begin();
+      float t;
+      if (index < cdf_size - 1) {
+        t = (x - cdf[index]) / (cdf[index + 1] - cdf[index]);
+      }
+      else {
+        t = 0.0f;
+        index = cdf_size - 1;
+      }
+      const float y = ((index + t) / (resolution - 1)) * (2.0f * range);
+      inv_cdf[half_size + i] = 0.5f * (1.0f + y);
+      inv_cdf[half_size - i] = 0.5f * (1.0f - y);
+    }
+  }
+  else {
+    for (int i = 0; i < resolution; i++) {
+      const float x = (i + 0.5f) * inv_resolution;
+      int index = upper_bound(cdf.begin(), cdf.end(), x) - cdf.begin() - 1;
+      float t;
+      if (index < cdf_size - 1) {
+        t = (x - cdf[index]) / (cdf[index + 1] - cdf[index]);
+      }
+      else {
+        t = 0.0f;
+        index = resolution;
+      }
+      inv_cdf[i] = from + range * (index + t) * inv_resolution;
+    }
+  }
+}
+
+CCL_NAMESPACE_END