Cycles: Add option to disable new Hair BVH

While it's an extra option added to the interface which might not be
fully obvious for artists, it allows to save up to 20% of memory in
hairy scenes.

This is high enough memory saver in my opinion which might become
handy for some production files where it's more important to make
scene to fit into memory rather than trying to use more optimal BVH
structure but go into swap or crash.

Reviewers: dingto, brecht

Reviewed By: dingto, brecht

Differential Revision: https://developer.blender.org/D2090

3 files changed, 7 insertions, 0 deletions

diff --git a/intern/cycles/blender/addon/properties.py b/intern/cycles/blender/addon/properties.py
index 140862721a8..193ef0cf505 100644
--- a/intern/cycles/blender/addon/properties.py
+++ b/intern/cycles/blender/addon/properties.py
@@ -503,6 +503,11 @@ class CyclesRenderSettings(bpy.types.PropertyGroup):
                 description="Use BVH spatial splits: longer builder time, faster render",
                 default=False,
                 )
+        cls.debug_use_hair_bvh = BoolProperty(
+                name="Use Hair BVH",
+                description="Use special type BVH optimized for hair. Uses more ram but renders faster",
+                default=True,
+                )
         cls.tile_order = EnumProperty(
                 name="Tile Order",
                 description="Tile order for rendering",
diff --git a/intern/cycles/blender/addon/ui.py b/intern/cycles/blender/addon/ui.py
index 120199479fe..10c8959172d 100644
--- a/intern/cycles/blender/addon/ui.py
+++ b/intern/cycles/blender/addon/ui.py
@@ -401,6 +401,7 @@ class CyclesRender_PT_performance(CyclesButtonsPanel, Panel):
 
         col.label(text="Acceleration structure:")
         col.prop(cscene, "debug_use_spatial_splits")
+        col.prop(cscene, "debug_use_hair_bvh")
 
 
 class CyclesRender_PT_layer_options(CyclesButtonsPanel, Panel):
diff --git a/intern/cycles/blender/blender_sync.cpp b/intern/cycles/blender/blender_sync.cpp
index 33084f1c163..e7e57b2be36 100644
--- a/intern/cycles/blender/blender_sync.cpp
+++ b/intern/cycles/blender/blender_sync.cpp
@@ -492,6 +492,7 @@ SceneParams BlenderSync::get_scene_params(BL::Scene& b_scene,
 		        SceneParams::BVH_STATIC);
 
 	params.use_bvh_spatial_split = RNA_boolean_get(&cscene, "debug_use_spatial_splits");
+	params.use_bvh_unaligned_nodes = RNA_boolean_get(&cscene, "debug_use_hair_bvh");
 
 	if(background && params.shadingsystem != SHADINGSYSTEM_OSL)
 		params.persistent_data = r.use_persistent_data();