1 files changed, 156 insertions, 0 deletions
diff --git a/intern/mikktspace/mikk_util.hh b/intern/mikktspace/mikk_util.hh
new file mode 100644
index 00000000000..224ed647b30
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+++ b/intern/mikktspace/mikk_util.hh
@@ -0,0 +1,156 @@
+/* SPDX-License-Identifier: Apache-2.0 */
+
+/** \file
+ * \ingroup mikktspace
+ */
+
+#pragma once
+
+#include <cassert>
+#include <cmath>
+
+#ifndef M_PI_F
+#  define M_PI_F (3.1415926535897932f) /* pi */
+#endif
+
+namespace mikk {
+
+inline bool not_zero(const float fX)
+{
+  return fabsf(fX) > FLT_MIN;
+}
+
+/* Helpers for (un)packing a 2-bit vertex index and a 30-bit face index to one integer. */
+static uint pack_index(const uint face, const uint vert)
+{
+  assert((vert & 0x3) == vert);
+  return (face << 2) | (vert & 0x3);
+}
+
+static void unpack_index(uint &face, uint &vert, const uint indexIn)
+{
+  vert = indexIn & 0x3;
+  face = indexIn >> 2;
+}
+
+/* From intern/cycles/util/math_fast.h */
+inline float fast_acosf(float x)
+{
+  const float f = fabsf(x);
+  /* clamp and crush denormals. */
+  const float m = (f < 1.0f) ? 1.0f - (1.0f - f) : 1.0f;
+  /* Based on http://www.pouet.net/topic.php?which=9132&page=2
+   * 85% accurate (ulp 0)
+   * Examined 2130706434 values of acos:
+   *   15.2000597 avg ulp diff, 4492 max ulp, 4.51803e-05 max error // without "denormal crush"
+   * Examined 2130706434 values of acos:
+   *   15.2007108 avg ulp diff, 4492 max ulp, 4.51803e-05 max error // with "denormal crush"
+   */
+  const float a = sqrtf(1.0f - m) *
+                  (1.5707963267f + m * (-0.213300989f + m * (0.077980478f + m * -0.02164095f)));
+  return x < 0 ? M_PI_F - a : a;
+}
+
+static uint rotl(uint x, uint k)
+{
+  return (x << k) | (x >> (32 - k));
+}
+
+static uint hash_uint3(uint kx, uint ky, uint kz)
+{
+  uint a, b, c;
+  a = b = c = 0xdeadbeef + (2 << 2) + 13;
+
+  c += kz;
+  b += ky;
+  a += kx;
+
+  c = (c ^ b) - rotl(b, 14);
+  a = (a ^ c) - rotl(c, 11);
+  b = (b ^ a) - rotl(a, 25);
+  c = (c ^ b) - rotl(b, 16);
+
+  return c;
+}
+
+static uint hash_uint3_fast(const uint x, const uint y, const uint z)
+{
+  return (x * 73856093) ^ (y * 19349663) ^ (z * 83492791);
+}
+
+static uint float_as_uint(const float v)
+{
+  return *((uint *)(&v));
+}
+
+static float uint_as_float(const uint v)
+{
+  return *((float *)(&v));
+}
+
+static uint hash_float3_fast(const float x, const float y, const float z)
+{
+  return hash_uint3_fast(float_as_uint(x), float_as_uint(y), float_as_uint(z));
+}
+
+static uint hash_float3x3(const float3 &x, const float3 &y, const float3 &z)
+{
+  return hash_uint3(hash_float3_fast(x.x, x.y, x.z),
+                    hash_float3_fast(y.x, y.y, y.z),
+                    hash_float3_fast(z.x, z.y, z.z));
+}
+
+template<typename T, typename KeyGetter>
+void radixsort(std::vector<T> &data, std::vector<T> &data2, KeyGetter getKey)
+{
+  typedef decltype(getKey(data[0])) key_t;
+  constexpr size_t datasize = sizeof(key_t);
+  static_assert(datasize % 2 == 0);
+  static_assert(std::is_integral<key_t>::value);
+
+  uint bins[datasize][257] = {0};
+
+  /* Count number of elements per bin. */
+  for (const T &item : data) {
+    key_t key = getKey(item);
+    for (uint pass = 0; pass < datasize; pass++)
+      bins[pass][((key >> (8 * pass)) & 0xff) + 1]++;
+  }
+
+  /* Compute prefix sum to find position of each bin in the sorted array. */
+  for (uint pass = 0; pass < datasize; pass++) {
+    for (uint i = 2; i < 256; i++) {
+      bins[pass][i] += bins[pass][i - 1];
+    }
+  }
+
+  int shift = 0;
+  for (uint pass = 0; pass < datasize; pass++, shift += 8) {
+    /* Insert the elements in their correct location based on their bin. */
+    for (const T &item : data) {
+      uint pos = bins[pass][(getKey(item) >> shift) & 0xff]++;
+      data2[pos] = item;
+    }
+
+    /* Swap arrays. */
+    std::swap(data, data2);
+  }
+}
+
+static void float_add_atomic(float *val, float add)
+{
+  /* Hacky, but atomic floats are only supported from C++20 onwards.
+   * This works in practise since std::atomic<uint32_t> is really just an uint32_t in memory,
+   * so this cast lets us do a 32-bit CAS operation (which is used to build the atomic float
+   * operation) without needing any external libraries or compiler-specific builtins. */
+  std::atomic<uint32_t> *atomic_val = reinterpret_cast<std::atomic<uint32_t> *>(val);
+  for (;;) {
+    uint32_t old_v = atomic_val->load();
+    uint32_t new_v = float_as_uint(uint_as_float(old_v) + add);
+    if (atomic_val->compare_exchange_weak(old_v, new_v)) {
+      return;
+    }
+  }
+}
+
+}  // namespace mikk