From f1034ec02beee2a497644fd91e680fd51ee1b5ac Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Thu, 16 Oct 2014 00:12:32 +0300
Subject: [PATCH] Delay loading matrices until they are needed

If all renderables use modern shaders, it's not necessary to touch the
system matrix stacks at all.  OpenGL ES 2.0 and OpenGL 3.0 core do not
even have system matrix stacks.
---
 source/renderer.cpp | 36 ++++++++++++++++++++++++++----------
 source/renderer.h   |  1 +
 2 files changed, 27 insertions(+), 10 deletions(-)

diff --git a/source/renderer.cpp b/source/renderer.cpp
index 606dd341..0207f937 100644
--- a/source/renderer.cpp
+++ b/source/renderer.cpp
@@ -22,7 +22,8 @@ namespace GL {
 
 Renderer::Renderer(const Camera *c):
 	mtx_stack(*this),
-	mtx_changed(false),
+	mtx_changed(true),
+	matrices_loaded(false),
 	camera(c),
 	state_stack(1),
 	lighting_changed(false),
@@ -32,11 +33,8 @@ Renderer::Renderer(const Camera *c):
 	shdata_stack.reserve(32);
 	state = &state_stack.back();
 
-	MatrixStack::modelview().push();
 	if(camera)
 	{
-		MatrixStack::projection().push();
-		camera->apply();
 		mtx_stack.load(camera->get_matrix());
 		standard_shdata.uniform("projection_matrix", camera->get_projection_matrix());
 	}
@@ -49,9 +47,12 @@ Renderer::Renderer(const Camera *c):
 
 Renderer::~Renderer()
 {
-	if(camera)
-		MatrixStack::projection().pop();
-	MatrixStack::modelview().pop();
+	if(matrices_loaded)
+	{
+		if(camera)
+			MatrixStack::projection().pop();
+		MatrixStack::modelview().pop();
+	}
 
 	Mesh::unbind();
 	Texturing::unbind();
@@ -157,6 +158,7 @@ void Renderer::escape()
 {
 	apply_state();
 	Buffer::unbind_from(ELEMENT_ARRAY_BUFFER);
+	matrices_loaded = false;
 }
 
 void Renderer::exclude(const Renderable &renderable)
@@ -282,10 +284,24 @@ void Renderer::apply_state()
 	else
 		WindingTest::unbind();
 
-	if(legacy_bindings && mtx_changed)
+	if(legacy_bindings)
 	{
-		MatrixStack::modelview() = mtx_stack.top();
-		mtx_changed = false;
+		if(!matrices_loaded)
+		{
+			MatrixStack::modelview().push();
+			if(camera)
+			{
+				MatrixStack::projection().push();
+				camera->apply();
+			}
+			matrices_loaded = true;
+		}
+
+		if(mtx_changed)
+		{
+			MatrixStack::modelview() = mtx_stack.top();
+			mtx_changed = false;
+		}
 	}
 }
 
diff --git a/source/renderer.h b/source/renderer.h
index 1be1a454..ccb23a22 100644
--- a/source/renderer.h
+++ b/source/renderer.h
@@ -91,6 +91,7 @@ private:
 
 	MtxStack mtx_stack;
 	bool mtx_changed;
+	bool matrices_loaded;
 	const Camera *camera;
 	std::vector<State> state_stack;
 	State *state;
-- 
2.45.2