Update ObjFileMtlImporter.cpp

Fixed grammar

code/ObjFileMtlImporter.cpp

@@ -59,8 +59,8 @@ static const std::string DiffuseTexture      = "map_Kd";
 static const std::string AmbientTexture      = "map_Ka";
 static const std::string SpecularTexture     = "map_Ks";
 static const std::string OpacityTexture      = "map_d";
-static const std::string EmmissiveTexture    = "map_emissive";
-static const std::string EmmissiveTexture_1  = "map_Ke";
+static const std::string EmissiveTexture    = "map_emissive";
+static const std::string EmissiveTexture_1  = "map_Ke";
 static const std::string BumpTexture1        = "map_bump";
 static const std::string BumpTexture2        = "map_Bump";
 static const std::string BumpTexture3        = "bump";