BGE: New hysteresis offset to improve LOD level transitions

This change introduces a new hysteresis parameter that it will be added
or subtracted to/from the LOD distance to avoid popping when a LOD
object moves close to the LOD transition continuously.

Then, we have the following:

- a new LOD Hysteresis setting per scene (default 10%) which is located
in Scene context --> Level of Detail panel. This scene parameter also
will active/deactive the scene hysteresis.
- and a new LOD Hysteresis setting per object (default 10%) which is
located in Object context --> Levels of Detail panel. The LOD hysteresis
setting per object (if active) will overwrite the hysteresis setting per
scene value.

For the new blends: the hysteresis setting per scene would be active by
default and the per object would be inactive by default.
For the old blends: both hysteresis settings (per scene and per object)
would be inactive by default. A quick way to take advantage of this
feature for old blends would be to activate the hysteresis parameter in
the scene context -> Level of Detail panel

Reviewers: campbellbarton, kupoman, moguri

Reviewed By: kupoman, moguri

Subscribers: nonamejuju, lordodin

Differential Revision: https://developer.blender.org/D957

1 files changed, 9 insertions, 0 deletions

diff --git a/source/gameengine/Ketsji/KX_Scene.h b/source/gameengine/Ketsji/KX_Scene.h
index 2e1ee9f101d..19873daabb3 100644
--- a/source/gameengine/Ketsji/KX_Scene.h
+++ b/source/gameengine/Ketsji/KX_Scene.h
@@ -295,6 +295,11 @@ protected:
 
 	KX_ObstacleSimulation* m_obstacleSimulation;
 
+	/**
+	 * Does this scene active the LoD Hysteresis?
+	 */
+	bool m_isActivedHysteresis;
+
 public:
 	KX_Scene(class SCA_IInputDevice* keyboarddevice,
 		class SCA_IInputDevice* mousedevice,
@@ -546,6 +551,10 @@ public:
 
 	// Update the mesh for objects based on level of detail settings
 	void UpdateObjectLods(void);
+
+	// Enable/disable LoD Hysteresis
+	void SetLodHysteresis(bool active);
+	bool IsActivedLodHysteresis();
 	
 	// Update the activity box settings for objects in this scene, if needed.
 	void UpdateObjectActivity(void);