1 files changed, 70 insertions, 0 deletions
diff --git a/intern/cycles/util/math_cdf.cpp b/intern/cycles/util/math_cdf.cpp
new file mode 100644
index 00000000000..02c6646f824
--- /dev/null
+++ b/intern/cycles/util/math_cdf.cpp
@@ -0,0 +1,70 @@
+/*
+ * Copyright 2011-2015 Blender Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "util/math_cdf.h"
+
+#include "util/algorithm.h"
+#include "util/math.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 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++) {
+      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;
+      }
+      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++) {
+      float x = from + range * (float)i * inv_resolution;
+      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 = resolution;
+      }
+      inv_cdf[i] = (index + t) * inv_resolution;
+    }
+  }
+}
+
+CCL_NAMESPACE_END