From 5592a115f0126ea8de1245e091338a8735b79d0e Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Fri, 4 Dec 2015 14:45:31 +0200
Subject: [PATCH] Cache renderables in SimpleScene into a vector

Set iteration is rather expensive, but I want to retain the O(logn)
performance of add and remove operations.
---
 source/simplescene.cpp | 21 +++++++++++++++++----
 source/simplescene.h   |  8 +++++++-
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/source/simplescene.cpp b/source/simplescene.cpp
index 73d08de2..4ccc714b 100644
--- a/source/simplescene.cpp
+++ b/source/simplescene.cpp
@@ -7,36 +7,49 @@ namespace GL {
 void SimpleScene::add(const Renderable &r)
 {
 	renderables.insert(&r);
+	cache.clear();
 }
 
 void SimpleScene::remove(const Renderable &r)
 {
 	renderables.erase(&r);
+	cache.clear();
+}
+
+void SimpleScene::populate_cache() const
+{
+	if(cache.empty() && !renderables.empty())
+	{
+		cache.reserve(renderables.size());
+		cache.insert(cache.end(), renderables.begin(), renderables.end());
+	}
 }
 
 void SimpleScene::setup_frame() const
 {
-	for(RenderableSet::const_iterator i=renderables.begin(); i!=renderables.end(); ++i)
+	populate_cache();
+	for(RenderableArray::const_iterator i=cache.begin(); i!=cache.end(); ++i)
 		(*i)->setup_frame();
 }
 
 void SimpleScene::finish_frame() const
 {
-	for(RenderableSet::const_iterator i=renderables.begin(); i!=renderables.end(); ++i)
+	for(RenderableArray::const_iterator i=cache.begin(); i!=cache.end(); ++i)
 		(*i)->finish_frame();
 }
 
 void SimpleScene::render(Renderer &renderer, const Tag &tag) const
 {
+	populate_cache();
 	if(setup_frustum(renderer))
 	{
-		for(RenderableSet::const_iterator i=renderables.begin(); i!=renderables.end(); ++i)
+		for(RenderableArray::const_iterator i=cache.begin(); i!=cache.end(); ++i)
 			if(!frustum_cull(**i))
 				renderer.render(**i, tag);
 	}
 	else
 	{
-		for(RenderableSet::const_iterator i=renderables.begin(); i!=renderables.end(); ++i)
+		for(RenderableArray::const_iterator i=cache.begin(); i!=cache.end(); ++i)
 			renderer.render(**i, tag);
 	}
 }
diff --git a/source/simplescene.h b/source/simplescene.h
index deba4d5f..ae7d169e 100644
--- a/source/simplescene.h
+++ b/source/simplescene.h
@@ -8,19 +8,25 @@ namespace Msp {
 namespace GL {
 
 /**
-The simplest possible Scene.  Rendering order is unspecified.
+A simple yet efficient scene.  Rendering order is unspecified.
 */
 class SimpleScene: public Scene
 {
 protected:
 	typedef std::set<const Renderable *> RenderableSet;
+	typedef std::vector<const Renderable *> RenderableArray;
 
 	RenderableSet renderables;
+	mutable RenderableArray cache;
 
 public:
 	virtual void add(const Renderable &);
 	virtual void remove(const Renderable &);
 
+private:
+	void populate_cache() const;
+
+public:
 	virtual void setup_frame() const;
 	virtual void finish_frame() const;
 
-- 
2.45.2