BGE Scenegraph and View frustrum culling improvement.

This commit contains a number of performance improvements for the
BGE in the Scenegraph (parent relation between objects in the
scene) and view frustrum culling.

The scenegraph improvement consists in avoiding position update
if the object has not moved since last update and the removal
of redundant updates and synchronization with the physics engine.

The view frustrum culling improvement consists in using the DBVT
broadphase facility of Bullet to build a tree of graphical objects
in the scene. The elements of the tree are Aabb boxes (Aligned 
Axis Bounding Boxes) enclosing the objects. This provides good
precision in closed and opened scenes. This new culling system
is enabled by default but just in case, it can be disabled with
a button in the World settings. There is no do_version in this
commit but it will be added before the 2.49 release. For now you
must manually enable the DBVT culling option in World settings
when you open an old file.

The above improvements speed up scenegraph and culling up to 5x.
However, this performance improvement is only visible when
you have hundreds or thousands of objects.

The main interest of the DBVT tree is to allow easy occlusion
culling and automatic LOD system. This will be the object of further
improvements.

1 files changed, 100 insertions, 7 deletions

diff --git a/source/gameengine/Physics/Bullet/CcdPhysicsEnvironment.cpp b/source/gameengine/Physics/Bullet/CcdPhysicsEnvironment.cpp
index dd21e58bd68..cef2f2477b7 100644
--- a/source/gameengine/Physics/Bullet/CcdPhysicsEnvironment.cpp
+++ b/source/gameengine/Physics/Bullet/CcdPhysicsEnvironment.cpp
@@ -18,6 +18,7 @@ subject to the following restrictions:
 
 #include "CcdPhysicsEnvironment.h"
 #include "CcdPhysicsController.h"
+#include "CcdGraphicController.h"
 
 #include <algorithm>
 #include "btBulletDynamicsCommon.h"
@@ -316,8 +317,10 @@ static void DrawAabb(btIDebugDraw* debugDrawer,const btVector3& from,const btVec
 
 
 
-CcdPhysicsEnvironment::CcdPhysicsEnvironment(btDispatcher* dispatcher,btOverlappingPairCache* pairCache)
-:m_numIterations(10),
+CcdPhysicsEnvironment::CcdPhysicsEnvironment(bool useDbvtCulling,btDispatcher* dispatcher,btOverlappingPairCache* pairCache)
+:m_cullingCache(NULL),
+m_cullingTree(NULL),
+m_numIterations(10),
 m_scalingPropagated(false),
 m_numTimeSubSteps(1),
 m_ccdMode(0),
@@ -350,6 +353,11 @@ m_ownDispatcher(NULL)
 	//m_broadphase = new btAxisSweep3(btVector3(-1000,-1000,-1000),btVector3(1000,1000,1000));
 	//m_broadphase = new btSimpleBroadphase();
 	m_broadphase = new btDbvtBroadphase();
+	// avoid any collision in the culling tree
+	if (useDbvtCulling) {
+		m_cullingCache = new btNullPairCache();
+		m_cullingTree = new btDbvtBroadphase(m_cullingCache);
+	}
 
 	m_filterCallback = new CcdOverlapFilterCallBack(this);
 	m_broadphase->getOverlappingPairCache()->setOverlapFilterCallback(m_filterCallback);
@@ -364,7 +372,6 @@ m_ownDispatcher(NULL)
 	m_gravity = btVector3(0.f,-10.f,0.f);
 	m_dynamicsWorld->setGravity(m_gravity);
 
-
 }
 
 void	CcdPhysicsEnvironment::addCcdPhysicsController(CcdPhysicsController* ctrl)
@@ -558,6 +565,41 @@ void CcdPhysicsEnvironment::refreshCcdPhysicsController(CcdPhysicsController* ct
 	}
 }
 
+void CcdPhysicsEnvironment::addCcdGraphicController(CcdGraphicController* ctrl)
+{
+	if (m_cullingTree)
+	{
+		btVector3	minAabb;
+		btVector3	maxAabb;
+		ctrl->getAabb(minAabb, maxAabb);
+
+		ctrl->setBroadphaseHandle(m_cullingTree->createProxy(
+				minAabb,
+				maxAabb,
+				INVALID_SHAPE_PROXYTYPE,	// this parameter is not used
+				ctrl,
+				0,							// this object does not collision with anything
+				0,
+				NULL,						// dispatcher => this parameter is not used
+				0));
+
+		assert(ctrl->getBroadphaseHandle());
+	}
+}
+
+void CcdPhysicsEnvironment::removeCcdGraphicController(CcdGraphicController* ctrl)
+{
+	if (m_cullingTree)
+	{
+		btBroadphaseProxy* bp = ctrl->getBroadphaseHandle();
+		if (bp)
+		{
+			m_cullingTree->destroyProxy(bp,NULL);
+			ctrl->setBroadphaseHandle(0);
+		}
+	}
+}
+
 void	CcdPhysicsEnvironment::beginFrame()
 {
 
@@ -593,10 +635,10 @@ bool	CcdPhysicsEnvironment::proceedDeltaTime(double curTime,float timeStep)
 		(*it)->SynchronizeMotionStates(timeStep);
 	}
 
-	for (it=m_controllers.begin(); it!=m_controllers.end(); it++)
-	{
-		(*it)->SynchronizeMotionStates(timeStep);
-	}
+	//for (it=m_controllers.begin(); it!=m_controllers.end(); it++)
+	//{
+	//	(*it)->SynchronizeMotionStates(timeStep);
+	//}
 
 	for (i=0;i<m_wrapperVehicles.size();i++)
 	{
@@ -1146,6 +1188,50 @@ PHY_IPhysicsController* CcdPhysicsEnvironment::rayTest(PHY_IRayCastFilterCallbac
 	return result.m_controller;
 }
 
+struct	DbvtCullingCallback : btDbvt::ICollide
+{
+	PHY_CullingCallback m_clientCallback;
+	void* m_userData;
+
+	DbvtCullingCallback(PHY_CullingCallback clientCallback, void* userData)
+	{
+		m_clientCallback = clientCallback;
+		m_userData = userData;
+	}
+
+	void Process(const btDbvtNode* node,btScalar depth)
+	{
+		Process(node);
+	}
+	void Process(const btDbvtNode* leaf)
+	{	
+		btBroadphaseProxy*	proxy=(btBroadphaseProxy*)leaf->data;
+		// the client object is a graphic controller
+		CcdGraphicController* ctrl = static_cast<CcdGraphicController*>(proxy->m_clientObject);
+		KX_ClientObjectInfo* info = (KX_ClientObjectInfo*)ctrl->getNewClientInfo();
+		if (info)
+			(*m_clientCallback)(info, m_userData);
+	}
+};
+
+bool CcdPhysicsEnvironment::cullingTest(PHY_CullingCallback callback, void* userData, PHY__Vector4 *planes, int nplanes)
+{
+	if (!m_cullingTree)
+		return false;
+	DbvtCullingCallback dispatcher(callback, userData);
+	btVector3 planes_n[5];
+	btScalar planes_o[5];
+	if (nplanes > 5)
+		nplanes = 5;
+	for (int i=0; i<nplanes; i++)
+	{
+		planes_n[i].setValue(planes[i][0], planes[i][1], planes[i][2]);
+		planes_o[i] = planes[i][3];
+	}
+	btDbvt::collideKDOP(m_cullingTree->m_sets[1].m_root,planes_n,planes_o,nplanes,dispatcher);
+	btDbvt::collideKDOP(m_cullingTree->m_sets[0].m_root,planes_n,planes_o,nplanes,dispatcher);		
+	return true;
+}
 
 
 int	CcdPhysicsEnvironment::getNumContactPoints()
@@ -1211,6 +1297,13 @@ CcdPhysicsEnvironment::~CcdPhysicsEnvironment()
 
 	if (NULL != m_broadphase)
 		delete m_broadphase;
+
+	if (NULL != m_cullingTree)
+		delete m_cullingTree;
+
+	if (NULL != m_cullingCache)
+		delete m_cullingCache;
+
 }