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

2 files changed, 27 insertions, 0 deletions

diff --git a/source/blender/makesrna/intern/rna_object.c b/source/blender/makesrna/intern/rna_object.c
index d8aa659b68e..a49388866a6 100644
--- a/source/blender/makesrna/intern/rna_object.c
+++ b/source/blender/makesrna/intern/rna_object.c
@@ -2089,6 +2089,14 @@ static void rna_def_object_lodlevel(BlenderRNA *brna)
 	RNA_def_property_ui_text(prop, "Distance", "Distance to begin using this level of detail");
 	RNA_def_property_update(prop, NC_OBJECT | ND_LOD, "rna_Object_lod_distance_update");
 
+	prop = RNA_def_property(srna, "object_hysteresis_percentage", PROP_INT, PROP_PERCENTAGE);
+	RNA_def_property_int_sdna(prop, NULL, "obhysteresis");
+	RNA_def_property_range(prop, 0, 100);
+	RNA_def_property_ui_range(prop, 0, 100, 10, 1);
+	RNA_def_property_ui_text(prop, "Hysteresis %", "Minimum distance change required to transition to the previous"
+								   " level of detail");
+	RNA_def_property_update(prop, NC_OBJECT | ND_LOD, NULL);
+
 	prop = RNA_def_property(srna, "object", PROP_POINTER, PROP_NONE);
 	RNA_def_property_pointer_sdna(prop, NULL, "source");
 	RNA_def_property_struct_type(prop, "Object");
@@ -2107,6 +2115,11 @@ static void rna_def_object_lodlevel(BlenderRNA *brna)
 	RNA_def_property_ui_text(prop, "Use Material", "Use the material from this object at this level of detail");
 	RNA_def_property_ui_icon(prop, ICON_MATERIAL, 0);
 	RNA_def_property_update(prop, NC_OBJECT | ND_LOD, NULL);
+
+	prop = RNA_def_property(srna, "use_object_hysteresis", PROP_BOOLEAN, PROP_NONE);
+	RNA_def_property_boolean_sdna(prop, NULL, "flags", OB_LOD_USE_HYST);
+	RNA_def_property_ui_text(prop, "Hysteresis Override", "Override LoD Hysteresis scene setting for this Lod Level");
+	RNA_def_property_update(prop, NC_OBJECT | ND_LOD, NULL);
 }
 
 
diff --git a/source/blender/makesrna/intern/rna_scene.c b/source/blender/makesrna/intern/rna_scene.c
index 2e941487e98..a0a0eedcfed 100644
--- a/source/blender/makesrna/intern/rna_scene.c
+++ b/source/blender/makesrna/intern/rna_scene.c
@@ -3886,6 +3886,20 @@ static void rna_def_scene_game_data(BlenderRNA *brna)
 
 	/* Nestled Data  */
 	rna_def_scene_game_recast_data(brna);
+
+	/* LoD */
+	prop = RNA_def_property(srna, "use_scene_hysteresis", PROP_BOOLEAN, PROP_NONE);
+	RNA_def_property_boolean_sdna(prop, NULL, "lodflag", SCE_LOD_USE_HYST);
+	RNA_def_property_ui_text(prop, "Hysteresis", "Use LoD Hysteresis setting for the scene");
+	RNA_def_property_update(prop, NC_SCENE, NULL);
+
+	prop = RNA_def_property(srna, "scene_hysteresis_percentage", PROP_INT, PROP_PERCENTAGE);
+	RNA_def_property_int_sdna(prop, NULL, "scehysteresis");
+	RNA_def_property_range(prop, 0, 100);
+	RNA_def_property_ui_range(prop, 0, 100, 10, 1);
+	RNA_def_property_ui_text(prop, "Hysteresis %", "Minimum distance change required to transition to the previous"
+								   " level of detail");
+	RNA_def_property_update(prop, NC_SCENE, NULL);
 }
 
 static void rna_def_gpu_dof_fx(BlenderRNA *brna)