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, 10 insertions, 3 deletions

diff --git a/source/gameengine/SceneGraph/SG_Spatial.h b/source/gameengine/SceneGraph/SG_Spatial.h
index 6ccec2aa9c1..c2ed80d21b2 100644
--- a/source/gameengine/SceneGraph/SG_Spatial.h
+++ b/source/gameengine/SceneGraph/SG_Spatial.h
@@ -61,7 +61,7 @@ protected:
 	
 	SG_BBox			m_bbox;
 	MT_Scalar		m_radius;
-	
+	bool			m_modified;
 
 public:
 
@@ -180,7 +180,7 @@ public:
 
 	MT_Transform GetWorldTransform() const;
 
-	bool	ComputeWorldTransforms(		const SG_Spatial *parent);
+	bool	ComputeWorldTransforms(const SG_Spatial *parent, bool& parentUpdated);
 
 	/**
 	 * Bounding box functions.
@@ -193,9 +193,14 @@ public:
 	
 	MT_Scalar Radius() const { return m_radius; }
 	void SetRadius(MT_Scalar radius) { m_radius = radius; }
+	bool IsModified() { return m_modified; }
 	
 protected:
 	friend class SG_Controller;
+	friend class KX_BoneParentRelation;
+	friend class KX_VertexParentRelation;
+	friend class KX_SlowParentRelation;
+	friend class KX_NormalParentRelation;
 	
 	/** 
 	 * Protected constructor this class is not
@@ -223,8 +228,10 @@ protected:
 		bool 
 	UpdateSpatialData(
 		const SG_Spatial *parent,
-		double time
+		double time,
+		bool& parentUpdated
 	);
+	void SetModified(bool modified) { m_modified = modified; }
 
 };