From d554a90d4301f1086047ae348c69d4348e74c1ce Mon Sep 17 00:00:00 2001
From: Martin Heistermann <git@mheistermann.de>
Date: Mon, 29 Aug 2022 18:28:04 +0200
Subject: [PATCH] OBJWriter performance: Add map from color to material index,
 avoids quadratic performance

---
 src/OpenMesh/Core/IO/writer/OBJWriter.cc | 35 +++++++++++++++---------
 src/OpenMesh/Core/IO/writer/OBJWriter.hh |  2 ++
 2 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/src/OpenMesh/Core/IO/writer/OBJWriter.cc b/src/OpenMesh/Core/IO/writer/OBJWriter.cc
index 145df5dc..97c0a00f 100644
--- a/src/OpenMesh/Core/IO/writer/OBJWriter.cc
+++ b/src/OpenMesh/Core/IO/writer/OBJWriter.cc
@@ -130,26 +130,31 @@ write(const std::string& _filename, BaseExporter& _be, Options _opt, std::stream
 
 size_t _OBJWriter_::getMaterial(OpenMesh::Vec3f _color) const
 {
-  for (size_t i=0; i < material_.size(); i++)
-    if(material_[i] == _color)
-      return i;
+  auto idx_it = material_idx_.find(_color);
+  if (idx_it != material_idx_.end()) {
+      return idx_it->second;
+  } else {
+      size_t idx = material_.size();
+      material_.push_back(_color);
+      material_idx_[_color] = idx;
 
-  //not found add new material
-  material_.push_back( _color );
-  return material_.size()-1;
+      return idx;
+  }
 }
 
 //-----------------------------------------------------------------------------
 
 size_t _OBJWriter_::getMaterial(OpenMesh::Vec4f _color) const
 {
-  for (size_t i=0; i < materialA_.size(); i++)
-    if(materialA_[i] == _color)
-      return i;
-
-  //not found add new material
-  materialA_.push_back( _color );
-  return materialA_.size()-1;
+  auto idx_it = materialA_idx_.find(_color);
+  if (idx_it != materialA_idx_.end()) {
+      return idx_it->second;
+  } else {
+      size_t idx = materialA_.size();
+      materialA_.push_back(_color);
+      materialA_idx_[_color] = idx;
+      return idx;
+  }
 }
 
 //-----------------------------------------------------------------------------
@@ -162,7 +167,9 @@ writeMaterial(std::ostream& _out, BaseExporter& _be, Options _opt) const
   OpenMesh::Vec4f cA;
 
   material_.clear();
+  material_idx_.clear();
   materialA_.clear();
+  materialA_idx_.clear();
 
   //iterate over faces
   for (size_t i=0, nF=_be.n_faces(); i<nF; ++i)
@@ -392,7 +399,9 @@ write(std::ostream& _out, BaseExporter& _be, Options _opt, std::streamsize _prec
   }
 
   material_.clear();
+  material_idx_.clear();
   materialA_.clear();
+  materialA_idx_.clear();
 
   return true;
 }
diff --git a/src/OpenMesh/Core/IO/writer/OBJWriter.hh b/src/OpenMesh/Core/IO/writer/OBJWriter.hh
index 6c05cb20..d9168aae 100644
--- a/src/OpenMesh/Core/IO/writer/OBJWriter.hh
+++ b/src/OpenMesh/Core/IO/writer/OBJWriter.hh
@@ -103,7 +103,9 @@ private:
   mutable std::string objName_;
 
   mutable std::vector< OpenMesh::Vec3f > material_;
+  mutable std::map< OpenMesh::Vec3f, size_t> material_idx_;
   mutable std::vector< OpenMesh::Vec4f > materialA_;
+  mutable std::map< OpenMesh::Vec4f, size_t> materialA_idx_;
 
   size_t getMaterial(OpenMesh::Vec3f _color) const;