From 5cb0d3eefb5dfed0be6a286d1bc70b1ccaae7752 Mon Sep 17 00:00:00 2001
From: Nate Koenig <natekoenig@gmail.com>
Date: Mon, 14 Aug 2023 08:40:45 -0700
Subject: [PATCH] World requires a scene and atmosphere

Signed-off-by: Nate Koenig <natekoenig@gmail.com>
---
 python/test/pyWorld_TEST.py |  2 +-
 src/World.cc                | 24 ++++++++++--------------
 src/World_TEST.cc           |  7 ++++++-
 3 files changed, 17 insertions(+), 16 deletions(-)

diff --git a/python/test/pyWorld_TEST.py b/python/test/pyWorld_TEST.py
index 08c62ab12..f77fcdc8e 100644
--- a/python/test/pyWorld_TEST.py
+++ b/python/test/pyWorld_TEST.py
@@ -202,7 +202,7 @@ def test_set_physics(self):
 
     def test_set_scene(self):
         world = World()
-        self.assertEqual(None, world.scene())
+        self.assertNotEqual(None, world.scene())
 
         scene = Scene()
         scene.set_ambient(Color.BLUE)
diff --git a/src/World.cc b/src/World.cc
index aacb571c9..461b3596a 100644
--- a/src/World.cc
+++ b/src/World.cc
@@ -47,8 +47,8 @@ class sdf::World::Implementation
   /// \return Errors, if any.
   public: Errors LoadSphericalCoordinates(sdf::ElementPtr _elem);
 
-  /// \brief Optional atmosphere model.
-  public: std::optional<sdf::Atmosphere> atmosphere;
+  /// \brief Required atmosphere model.
+  public: sdf::Atmosphere atmosphere;
 
   /// \brief Audio device name
   public: std::string audioDevice = "default";
@@ -60,8 +60,8 @@ class sdf::World::Implementation
   /// \brief Optional Gui parameters.
   public: std::optional<sdf::Gui> gui;
 
-  /// \brief Optional Scene parameters.
-  public: std::optional<sdf::Scene> scene;
+  /// \brief Required scene parameters.
+  public: sdf::Scene scene;
 
   /// \brief The frames specified in this world.
   public: std::vector<Frame> frames;
@@ -180,9 +180,8 @@ Errors World::Load(sdf::ElementPtr _sdf, const ParserConfig &_config)
   // Read the atmosphere element
   if (_sdf->HasElement("atmosphere"))
   {
-    this->dataPtr->atmosphere.emplace();
     Errors atmosphereLoadErrors =
-      this->dataPtr->atmosphere->Load(_sdf->GetElement("atmosphere"));
+      this->dataPtr->atmosphere.Load(_sdf->GetElement("atmosphere"));
     errors.insert(errors.end(), atmosphereLoadErrors.begin(),
         atmosphereLoadErrors.end());
   }
@@ -314,9 +313,8 @@ Errors World::Load(sdf::ElementPtr _sdf, const ParserConfig &_config)
   // Load the Scene
   if (_sdf->HasElement("scene"))
   {
-    this->dataPtr->scene.emplace();
     Errors sceneLoadErrors =
-        this->dataPtr->scene->Load(_sdf->GetElement("scene"), _config);
+        this->dataPtr->scene.Load(_sdf->GetElement("scene"), _config);
     errors.insert(errors.end(), sceneLoadErrors.begin(), sceneLoadErrors.end());
   }
 
@@ -459,7 +457,7 @@ Model *World::ModelByName(const std::string &_name)
 /////////////////////////////////////////////////
 const sdf::Atmosphere *World::Atmosphere() const
 {
-  return optionalToPointer(this->dataPtr->atmosphere);
+  return &(this->dataPtr->atmosphere);
 }
 
 /////////////////////////////////////////////////
@@ -497,7 +495,7 @@ void World::SetGui(const sdf::Gui &_gui)
 /////////////////////////////////////////////////
 const sdf::Scene *World::Scene() const
 {
-  return optionalToPointer(this->dataPtr->scene);
+  return &(this->dataPtr->scene);
 }
 
 /////////////////////////////////////////////////
@@ -1033,16 +1031,14 @@ sdf::ElementPtr World::ToElement(const OutputConfig &_config) const
   }
 
   // Atmosphere
-  if (this->dataPtr->atmosphere)
-    elem->InsertElement(this->dataPtr->atmosphere->ToElement(), true);
+  elem->InsertElement(this->dataPtr->atmosphere.ToElement(), true);
 
   // Gui
   if (this->dataPtr->gui)
     elem->InsertElement(this->dataPtr->gui->ToElement(), true);
 
   // Scene
-  if (this->dataPtr->scene)
-    elem->InsertElement(this->dataPtr->scene->ToElement(), true);
+  elem->InsertElement(this->dataPtr->scene.ToElement(), true);
 
   // Audio
   if (this->dataPtr->audioDevice != "default")
diff --git a/src/World_TEST.cc b/src/World_TEST.cc
index 9e9174a4f..b1f93b92e 100644
--- a/src/World_TEST.cc
+++ b/src/World_TEST.cc
@@ -39,6 +39,11 @@ TEST(DOMWorld, Construction)
   EXPECT_STREQ("default", world.AudioDevice().c_str());
   EXPECT_EQ(gz::math::Vector3d::Zero, world.WindLinearVelocity());
 
+  // The scene and atmosphere are requred, per the SDF spec. Make sure
+  // that they have been created.
+  EXPECT_TRUE(world.Scene());
+  EXPECT_TRUE(world.Atmosphere());
+
   EXPECT_EQ(0u, world.ModelCount());
   EXPECT_EQ(nullptr, world.ModelByIndex(0));
   EXPECT_EQ(nullptr, world.ModelByIndex(1));
@@ -358,7 +363,7 @@ TEST(DOMWorld, SetGui)
 TEST(DOMWorld, SetScene)
 {
   sdf::World world;
-  EXPECT_EQ(nullptr, world.Scene());
+  EXPECT_NE(nullptr, world.Scene());
 
   sdf::Scene scene;
   scene.SetAmbient(gz::math::Color::Blue);