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diff --git a/intern/cycles/kernel/sample/mis.h b/intern/cycles/kernel/sample/mis.h
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+/*
+ * Parts adapted from Open Shading Language with this license:
+ *
+ * Copyright (c) 2009-2010 Sony Pictures Imageworks Inc., et al.
+ * All Rights Reserved.
+ *
+ * Modifications Copyright 2011, Blender Foundation.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ * * Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the distribution.
+ * * Neither the name of Sony Pictures Imageworks nor the names of its
+ *   contributors may be used to endorse or promote products derived from
+ *   this software without specific prior written permission.
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+CCL_NAMESPACE_BEGIN
+
+/* Multiple importance sampling utilities. */
+
+ccl_device float balance_heuristic(float a, float b)
+{
+  return (a) / (a + b);
+}
+
+ccl_device float balance_heuristic_3(float a, float b, float c)
+{
+  return (a) / (a + b + c);
+}
+
+ccl_device float power_heuristic(float a, float b)
+{
+  return (a * a) / (a * a + b * b);
+}
+
+ccl_device float power_heuristic_3(float a, float b, float c)
+{
+  return (a * a) / (a * a + b * b + c * c);
+}
+
+ccl_device float max_heuristic(float a, float b)
+{
+  return (a > b) ? 1.0f : 0.0f;
+}
+
+CCL_NAMESPACE_END