1 files changed, 35 insertions, 0 deletions
diff --git a/intern/cycles/kernel/sample/util.h b/intern/cycles/kernel/sample/util.h
new file mode 100644
index 00000000000..29cda179aa2
--- /dev/null
+++ b/intern/cycles/kernel/sample/util.h
@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: Apache-2.0
+ * Copyright 2011-2022 Blender Foundation */
+
+#pragma once
+
+#include "util/types.h"
+
+CCL_NAMESPACE_BEGIN
+
+/*
+ * Performs base-2 Owen scrambling on a reversed-bit unsigned integer.
+ *
+ * This is equivalent to the Laine-Karras permutation, but much higher
+ * quality.  See https://psychopath.io/post/2021_01_30_building_a_better_lk_hash
+ */
+ccl_device_inline uint reversed_bit_owen(uint n, uint seed)
+{
+  n ^= n * 0x3d20adea;
+  n += seed;
+  n *= (seed >> 16) | 1;
+  n ^= n * 0x05526c56;
+  n ^= n * 0x53a22864;
+
+  return n;
+}
+
+/*
+ * Performs base-2 Owen scrambling on an unsigned integer.
+ */
+ccl_device_inline uint nested_uniform_scramble(uint i, uint seed)
+{
+  return reverse_integer_bits(reversed_bit_owen(reverse_integer_bits(i), seed));
+}
+
+CCL_NAMESPACE_END