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.

3 files changed, 7 insertions, 1 deletions

diff --git a/source/blender/blenkernel/intern/world.c b/source/blender/blenkernel/intern/world.c
index 2e89ce3f805..594d18f1ca7 100644
--- a/source/blender/blenkernel/intern/world.c
+++ b/source/blender/blenkernel/intern/world.c
@@ -106,6 +106,7 @@ World *add_world(char *name)
 	wrld->ao_approx_error= 0.25f;
 	
 	wrld->physicsEngine= WOPHY_BULLET;//WOPHY_SUMO; Bullet by default
+	wrld->mode = WO_DBVT_CAMERA_CULLING;	// DBVT culling by default
 	wrld->preview = NULL;
 
 	return wrld;
diff --git a/source/blender/makesdna/DNA_world_types.h b/source/blender/makesdna/DNA_world_types.h
index ab7e25190ad..a51e9704be2 100644
--- a/source/blender/makesdna/DNA_world_types.h
+++ b/source/blender/makesdna/DNA_world_types.h
@@ -84,6 +84,8 @@ typedef struct World {
 	 * bit 1: Do stars
 	 * bit 2: (reserved) depth of field
 	 * bit 3: (gameengine): Activity culling is enabled.
+	 * bit 4: ambient occlusion
+	 * bit 5: (gameengine) : enable Bullet DBVT tree for view frustrum culling 
 	 */
 	short mode;
 	int physicsEngine;	/* here it's aligned */
@@ -133,6 +135,7 @@ typedef struct World {
 #define WO_DOF                 4
 #define WO_ACTIVITY_CULLING	   8
 #define WO_AMB_OCC	   		  16
+#define WO_DBVT_CAMERA_CULLING  32
 
 /* aomix */
 #define WO_AOADD	0
diff --git a/source/blender/src/buttons_shading.c b/source/blender/src/buttons_shading.c
index fe4649f31f4..e68c86349ce 100644
--- a/source/blender/src/buttons_shading.c
+++ b/source/blender/src/buttons_shading.c
@@ -2181,7 +2181,7 @@ static void world_panel_mistaph(World *wrld)
 	uiSetButLock(wrld->id.lib!=0, ERROR_LIBDATA_MESSAGE);
 
 #if GAMEBLENDER == 1
-	uiDefButI(block, MENU, 1, 
+	uiDefButI(block, MENU, B_REDR, 
 #ifdef USE_ODE
 			  "Physics %t|None %x0|Sumo %x2|Ode %x4 |Bullet %x5",
 #else
@@ -2198,6 +2198,8 @@ static void world_panel_mistaph(World *wrld)
 	
 	/* Gravitation for the game worlds */
 	uiDefButF(block, NUMSLI,0, "Grav ", 150,180,150,19,	&(wrld->gravity), 0.0, 25.0, 0, 0,  "Sets the gravitation constant of the game world");
+	if (wrld->physicsEngine == WOPHY_BULLET)
+		uiDefButBitS(block, TOG, WO_DBVT_CAMERA_CULLING, 0, "DBVT culling",	10,160,140,19, &wrld->mode, 0, 0, 0, 0, "Toggles use of optimized Bullet DBVT tree for camera culling");
 #endif
 
 	uiBlockSetCol(block, TH_BUT_SETTING1);