BGE performance: second round of scenegraph improvement.

Use dynamic linked list to handle scenegraph rather than dumb scan
of the whole tree. The performance improvement depends on the fraction
of moving objects. If most objects are static, the speed up is 
considerable. The following table compares the time spent on 
scenegraph before and after this commit on a scene with 10000 objects
in various configuratons:

Scenegraph time (ms)              Before         After
(includes culling)

All objects static,               8.8            1.7  
all visible but small fraction          
in the view frustrum

All objects static,               7,5            0.01
all invisible.

All objects moving,               14.1           8.4
all visible but small fraction
in the view frustrum

This tables shows that static and invisible objects take no CPU at all
for scenegraph and culling. In the general case, this commit will 
speed up the scenegraph between 2x and 5x. Compared to 2.48a, it should
be between 4x and 10x faster. Further speed up is possible by making
the scenegraph cache-friendly.

Next round of performance improvement will be on the rasterizer: use
the same dynamic linked list technique for the mesh slots.

1 files changed, 6 insertions, 4 deletions

diff --git a/source/gameengine/Ketsji/KX_SG_NodeRelationships.cpp b/source/gameengine/Ketsji/KX_SG_NodeRelationships.cpp
index c3b0c21c8e0..c49b6d671a7 100644
--- a/source/gameengine/Ketsji/KX_SG_NodeRelationships.cpp
+++ b/source/gameengine/Ketsji/KX_SG_NodeRelationships.cpp
@@ -63,7 +63,7 @@ UpdateChildCoordinates(
 
 	if (parent==NULL) { /* Simple case */
 		child->SetWorldFromLocalTransform();
-		child->SetModified(false);
+		child->ClearModified();
 		return true; //false;
 	}
 	else {
@@ -75,7 +75,7 @@ UpdateChildCoordinates(
 		child->SetWorldScale(p_world_scale * child->GetLocalScale());
 		child->SetWorldOrientation(p_world_rotation * child->GetLocalOrientation());
 		child->SetWorldPosition(p_world_pos + p_world_scale * (p_world_rotation * child->GetLocalPosition()));
-		child->SetModified(false);
+		child->ClearModified();
 		return true;
 	}
 }
@@ -137,7 +137,7 @@ UpdateChildCoordinates(
 		child->SetWorldPosition(child->GetLocalPosition());
 	
 	child->SetWorldOrientation(child->GetLocalOrientation());
-	child->SetModified(false);
+	child->ClearModified();
 	return true; //parent != NULL;
 }
 
@@ -259,7 +259,9 @@ UpdateChildCoordinates(
 	child->SetWorldScale(child_w_scale);
 	child->SetWorldPosition(child_w_pos);
 	child->SetWorldOrientation(child_w_rotation);
-	child->SetModified(false);
+	child->ClearModified();
+	// this node must always be updated, so reschedule it for next time
+	child->ActivateRecheduleUpdateCallback();
 	
 	return true; //parent != NULL;
 }