1 files changed, 87 insertions, 0 deletions
diff --git a/source/blender/blenkernel/intern/cryptomatte.c b/source/blender/blenkernel/intern/cryptomatte.c
new file mode 100644
index 00000000000..6570ffce920
--- /dev/null
+++ b/source/blender/blenkernel/intern/cryptomatte.c
@@ -0,0 +1,87 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * The Original Code is Copyright (C) 2008 Blender Foundation.
+ * All rights reserved.
+ */
+
+/** \file
+ * \ingroup bke
+ */
+
+#include "BKE_cryptomatte.h"
+
+#include "DNA_material_types.h"
+#include "DNA_object_types.h"
+
+#include "BLI_compiler_attrs.h"
+#include "BLI_hash_mm3.h"
+#include "BLI_string.h"
+#include <string.h>
+
+static uint32_t cryptomatte_hash(const ID *id)
+{
+  const char *name = &id->name[2];
+  const int len = BLI_strnlen(name, MAX_NAME - 2);
+  uint32_t cryptohash_int = BLI_hash_mm3((const unsigned char *)name, len, 0);
+  return cryptohash_int;
+}
+
+uint32_t BKE_cryptomatte_object_hash(const Object *object)
+{
+  return cryptomatte_hash(&object->id);
+}
+
+uint32_t BKE_cryptomatte_material_hash(const Material *material)
+{
+  if (material == NULL) {
+    return 0.0f;
+  }
+  return cryptomatte_hash(&material->id);
+}
+
+uint32_t BKE_cryptomatte_asset_hash(const Object *object)
+{
+  const Object *asset_object = object;
+  while (asset_object->parent != NULL) {
+    asset_object = asset_object->parent;
+  }
+  return cryptomatte_hash(&asset_object->id);
+}
+
+/* Convert a cryptomatte hash to a float.
+ *
+ * Cryptomatte hashes are stored in float textures and images. The conversion is taken from the
+ * cryptomatte specification. See Floating point conversion section in
+ * https://github.com/Psyop/Cryptomatte/blob/master/specification/cryptomatte_specification.pdf.
+ *
+ * The conversion uses as many 32 bit floating point values as possible to minimize hash
+ * collisions. Unfortunately not all 32 bits can be as NaN and Inf can be problematic.
+ *
+ * Note that this conversion assumes to be running on a L-endian system. */
+float BKE_cryptomatte_hash_to_float(uint32_t cryptomatte_hash)
+{
+  uint32_t mantissa = cryptomatte_hash & ((1 << 23) - 1);
+  uint32_t exponent = (cryptomatte_hash >> 23) & ((1 << 8) - 1);
+  exponent = MAX2(exponent, (uint32_t)1);
+  exponent = MIN2(exponent, (uint32_t)254);
+  exponent = exponent << 23;
+  uint32_t sign = (cryptomatte_hash >> 31);
+  sign = sign << 31;
+  uint32_t float_bits = sign | exponent | mantissa;
+  float f;
+  memcpy(&f, &float_bits, sizeof(uint32_t));
+  return f;
+}