From: Mikko Rasa <tdb@tdb.fi>
Date: Fri, 4 Dec 2015 18:43:07 +0000 (+0200)
Subject: Use a persistent sorted array in ZSortedScene
X-Git-Url: http://git.tdb.fi/?p=libs%2Fgl.git;a=commitdiff_plain;h=af0077ac71c51aeed63bc0222fe4650d5077478a

Use a persistent sorted array in ZSortedScene

Typically the order of renderables changes very little between frames, so
it's possible to use insertion sort which is very fast for almost-sorted
arrays.
---

diff --git a/source/zsortedscene.cpp b/source/zsortedscene.cpp
index 0d50ae1e..709c5c26 100644
--- a/source/zsortedscene.cpp
+++ b/source/zsortedscene.cpp
@@ -12,6 +12,18 @@ ZSortedScene::ZSortedScene():
 	reference(FURTHEST)
 { }
 
+void ZSortedScene::add(const Renderable &r)
+{
+	if(renderables.insert(&r).second && !sorted_cache.empty())
+		sorted_cache.push_back(&r);
+}
+
+void ZSortedScene::remove(const Renderable &r)
+{
+	renderables.erase(&r);
+	sorted_cache.clear();
+}
+
 void ZSortedScene::set_order(SortOrder o)
 {
 	order = o;
@@ -24,12 +36,22 @@ void ZSortedScene::set_reference(DepthReference r)
 
 void ZSortedScene::render(Renderer &renderer, const Tag &tag) const
 {
+	if(renderables.empty())
+		return;
+
 	const Camera *camera = renderer.get_camera();
 	if(!camera)
-		return SimpleScene::render(renderer, tag);
+	{
+		for(RenderableSet::const_iterator i=renderables.begin(); i!=renderables.end(); ++i)
+			renderer.render(**i, tag);
+		return;
+	}
 
-	std::vector<DepthRenderable> sorted_renderables;
-	sorted_renderables.reserve(renderables.size());
+	if(sorted_cache.empty())
+	{
+		sorted_cache.reserve(renderables.size());
+		sorted_cache.insert(sorted_cache.end(), renderables.begin(), renderables.end());
+	}
 
 	const Vector3 &camera_pos = camera->get_position();
 	const Vector3 &look_dir = camera->get_look_direction();
@@ -37,29 +59,54 @@ void ZSortedScene::render(Renderer &renderer, const Tag &tag) const
 	float sign = 1.0f-order*2.0f;
 
 	bool use_frustum = setup_frustum(renderer);
-	for(RenderableSet::const_iterator i=renderables.begin(); i!=renderables.end(); ++i)
-		if(!use_frustum || !frustum_cull(**i))
+	for(SortedArray::iterator i=sorted_cache.begin(); i!=sorted_cache.end(); ++i)
+	{
+		i->in_frustum = (!use_frustum || !frustum_cull(*i->renderable));
+		if(i->in_frustum)
 		{
-			float z = 0;
-			if(const Matrix *model_matrix = (*i)->get_matrix())
+			if(const Matrix *model_matrix = i->renderable->get_matrix())
 			{
-				if(const Geometry::BoundingSphere<float, 3> *bsphere = (*i)->get_bounding_sphere())
-					z = dot(*model_matrix*bsphere->get_center()-camera_pos, look_dir)+bsphere->get_radius()*radius_factor;
+				if(const Geometry::BoundingSphere<float, 3> *bsphere = i->renderable->get_bounding_sphere())
+					i->depth = dot(*model_matrix*bsphere->get_center()-camera_pos, look_dir)+bsphere->get_radius()*radius_factor;
 				else
-					z = dot(*model_matrix*Vector3()-camera_pos, look_dir);
+					i->depth = dot(*model_matrix*Vector3()-camera_pos, look_dir);
+				i->depth *= sign;
 			}
-			sorted_renderables.push_back(DepthRenderable(z*sign, *i));
+			else
+				i->depth = 0;
 		}
+	}
 
-	sort(sorted_renderables.begin(), sorted_renderables.end());
+	for(SortedArray::iterator i=sorted_cache.begin(), j=i; i!=sorted_cache.end(); ++i)
+		if(i->in_frustum)
+		{
+			if(i!=j)
+				swap(*i, *j);
+
+			if(j!=sorted_cache.begin() && *j<*(j-1))
+			{
+				SortedRenderable sr = *j;
+				SortedArray::iterator k = j-1;
+				*j = *k;
+				while(k!=sorted_cache.begin() && sr<*(k-1))
+				{
+					*k = *(k-1);
+					--k;
+				}
+				*k = sr;
+			}
+
+			++j;
+		}
 
-	for(vector<DepthRenderable>::const_iterator i=sorted_renderables.begin(); i!=sorted_renderables.end(); ++i)
-		i->renderable->render(renderer, tag);
+	for(SortedArray::const_iterator i=sorted_cache.begin(); (i!=sorted_cache.end() && i->in_frustum); ++i)
+		renderer.render(*i->renderable, tag);
 }
 
 
-ZSortedScene::DepthRenderable::DepthRenderable(float d, const Renderable *r):
-	depth(d),
+ZSortedScene::SortedRenderable::SortedRenderable(const Renderable *r):
+	in_frustum(false),
+	depth(0.0f),
 	renderable(r)
 { }
 
diff --git a/source/zsortedscene.h b/source/zsortedscene.h
index f9f6f7ee..5c876697 100644
--- a/source/zsortedscene.h
+++ b/source/zsortedscene.h
@@ -23,25 +23,34 @@ enum DepthReference
 Sorts renderables by their distance from the camera before rendering.  Requires
 renderables to have a matrix.
 */
-class ZSortedScene: public SimpleScene
+class ZSortedScene: public Scene
 {
 private:
-	struct DepthRenderable
+	struct SortedRenderable
 	{
+		bool in_frustum;
 		float depth;
 		const Renderable *renderable;
 
-		DepthRenderable(float, const Renderable *);
+		SortedRenderable(const Renderable *);
 
-		bool operator<(const DepthRenderable &o) const { return depth<o.depth; }
+		bool operator<(const SortedRenderable &o) const { return depth<o.depth; }
 	};
 
+	typedef std::set<const Renderable *> RenderableSet;
+	typedef std::vector<SortedRenderable> SortedArray;
+
+	RenderableSet renderables;
 	SortOrder order;
 	DepthReference reference;
+	mutable SortedArray sorted_cache;
 
 public:
 	ZSortedScene();
 
+	virtual void add(const Renderable &);
+	virtual void remove(const Renderable &);
+
 	/// Sets the sort order.  Default is back to front.
 	void set_order(SortOrder);