From f6f0be47eaecfebc29fe9e9221ee437607d3b820 Mon Sep 17 00:00:00 2001
From: turanszkij <turanszkij@gmail.com>
Date: Tue, 9 Apr 2019 12:35:05 +0100
Subject: [PATCH] obj import hash fix

---
 Editor/ModelImporter_OBJ.cpp | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/Editor/ModelImporter_OBJ.cpp b/Editor/ModelImporter_OBJ.cpp
index f0a9ea524..79fb867cd 100644
--- a/Editor/ModelImporter_OBJ.cpp
+++ b/Editor/ModelImporter_OBJ.cpp
@@ -15,6 +15,13 @@ using namespace wiECS;
 // Transform the data from OBJ space to engine-space:
 static const bool transform_to_LH = true;
 
+template <class T>
+inline void hash_combine(std::size_t& seed, const T& v)
+{
+	std::hash<T> hasher;
+	seed ^= hasher(v) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
+}
+
 void ImportModel_OBJ(const std::string& fileName, Scene& scene)
 {
 	string directory, name;
@@ -164,13 +171,11 @@ void ImportModel_OBJ(const std::string& fileName, Scene& scene)
 					}
 
 					// eliminate duplicate vertices by means of hashing:
-					size_t hashes[] = {
-						hash<int>{}(index.vertex_index),
-						hash<int>{}(index.normal_index),
-						hash<int>{}(index.texcoord_index),
-						hash<int>{}(materialIndex),
-					};
-					size_t vertexHash = (((hashes[0] ^ (hashes[1] << 1) >> 1) ^ (hashes[2] << 1)) >> 1) ^ (hashes[3] << 1);
+					size_t vertexHash = 0;
+					hash_combine(vertexHash, index.vertex_index);
+					hash_combine(vertexHash, index.normal_index);
+					hash_combine(vertexHash, index.texcoord_index);
+					hash_combine(vertexHash, materialIndex);
 
 					if (uniqueVertices.count(vertexHash) == 0)
 					{