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, 29 insertions, 1 deletions

diff --git a/release/scripts/startup/bl_ui/properties_game.py b/release/scripts/startup/bl_ui/properties_game.py
index 32a8e734ab6..8ef9a083104 100644
--- a/release/scripts/startup/bl_ui/properties_game.py
+++ b/release/scripts/startup/bl_ui/properties_game.py
@@ -523,7 +523,27 @@ class SCENE_PT_game_navmesh(SceneButtonsPanel, Panel):
         row.prop(rd, "sample_max_error")
 
 
-class WorldButtonsPanel:
+class SCENE_PT_game_hysteresis(SceneButtonsPanel, Panel):
+    bl_label = "Level of Detail"
+    COMPAT_ENGINES = {'BLENDER_GAME'}
+
+    @classmethod
+    def poll(cls, context):
+        scene = context.scene
+        return (scene and scene.render.engine in cls.COMPAT_ENGINES)
+
+    def draw(self, context):
+        layout = self.layout
+        gs = context.scene.game_settings
+
+        row = layout.row()
+        row.prop(gs, "use_scene_hysteresis", text="Hysteresis")
+        row = layout.row()
+        row.active = gs.use_scene_hysteresis
+        row.prop(gs, "scene_hysteresis_percentage", text="")
+
+
+class WorldButtonsPanel():
     bl_space_type = 'PROPERTIES'
     bl_region_type = 'WINDOW'
     bl_context = "world"
@@ -765,6 +785,7 @@ class OBJECT_PT_levels_of_detail(ObjectButtonsPanel, Panel):
     def draw(self, context):
         layout = self.layout
         ob = context.object
+        gs = context.scene.game_settings
 
         col = layout.column()
 
@@ -782,6 +803,13 @@ class OBJECT_PT_levels_of_detail(ObjectButtonsPanel, Panel):
             row.prop(level, "use_mesh", text="")
             row.prop(level, "use_material", text="")
 
+            row = box.row()
+            row.active = gs.use_scene_hysteresis
+            row.prop(level, "use_object_hysteresis", text="Hysteresis Override")
+            row = box.row()
+            row.active = gs.use_scene_hysteresis and level.use_object_hysteresis
+            row.prop(level, "object_hysteresis_percentage", text="")
+
         row = col.row(align=True)
         row.operator("object.lod_add", text="Add", icon='ZOOMIN')
         row.menu("OBJECT_MT_lod_tools", text="", icon='TRIA_DOWN')