Cycles: Expose volume voxel data interpolation to the interface

It is per-material setting which could be found under the Volume settings
in the material and world context buttons.

There could still be some code-wise improvements, like using variable-size
macro for interp3d instead of having interp3d_ex to which you can pass the
interpolation method.

3 files changed, 23 insertions, 0 deletions

diff --git a/intern/cycles/blender/addon/properties.py b/intern/cycles/blender/addon/properties.py
index 597ac1a9ce0..05a6f70d423 100644
--- a/intern/cycles/blender/addon/properties.py
+++ b/intern/cycles/blender/addon/properties.py
@@ -114,6 +114,11 @@ enum_volume_sampling = (
     ('MULTIPLE_IMPORTANCE', "Multiple Importance", "Combine distance and equi-angular sampling for volumes where neither method is ideal"),
     )
 
+enum_volume_interpolation = (
+    ('LINEAR', "Linear", "Good smoothness and speed"),
+    ('CUBIC', 'Cubic', 'Smoothed high quality interpolation, but slower')
+    )
+
 
 class CyclesRenderSettings(bpy.types.PropertyGroup):
     @classmethod
@@ -617,6 +622,13 @@ class CyclesMaterialSettings(bpy.types.PropertyGroup):
                 default='DISTANCE',
                 )
 
+        cls.volume_interpolation = EnumProperty(
+                name="Volume Interpolation",
+                description="Interpolation method to use for volumes",
+                items=enum_volume_interpolation,
+                default='LINEAR',
+                )
+
     @classmethod
     def unregister(cls):
         del bpy.types.Material.cycles
@@ -693,6 +705,13 @@ class CyclesWorldSettings(bpy.types.PropertyGroup):
                 default='EQUIANGULAR',
                 )
 
+        cls.volume_interpolation = EnumProperty(
+                name="Volume Interpolation",
+                description="Interpolation method to use for volumes",
+                items=enum_volume_interpolation,
+                default='LINEAR',
+                )
+
     @classmethod
     def unregister(cls):
         del bpy.types.World.cycles
diff --git a/intern/cycles/blender/addon/ui.py b/intern/cycles/blender/addon/ui.py
index 8743aa445be..6a08b47b01f 100644
--- a/intern/cycles/blender/addon/ui.py
+++ b/intern/cycles/blender/addon/ui.py
@@ -936,6 +936,7 @@ class CyclesWorld_PT_settings(CyclesButtonsPanel, Panel):
         sub = col.column()
         sub.active = use_cpu(context)
         sub.prop(cworld, "volume_sampling", text="")
+        sub.prop(cworld, "volume_interpolation", text="")
         col.prop(cworld, "homogeneous_volume", text="Homogeneous")
 
 
@@ -1040,6 +1041,7 @@ class CyclesMaterial_PT_settings(CyclesButtonsPanel, Panel):
         sub = col.column()
         sub.active = use_cpu(context)
         sub.prop(cmat, "volume_sampling", text="")
+        col.prop(cmat, "volume_interpolation", text="")
         col.prop(cmat, "homogeneous_volume", text="Homogeneous")
 
 
diff --git a/intern/cycles/blender/blender_shader.cpp b/intern/cycles/blender/blender_shader.cpp
index 33c7bf5f859..97f2ecc1a6c 100644
--- a/intern/cycles/blender/blender_shader.cpp
+++ b/intern/cycles/blender/blender_shader.cpp
@@ -1015,6 +1015,7 @@ void BlenderSync::sync_materials(bool update_all)
 			shader->use_transparent_shadow = get_boolean(cmat, "use_transparent_shadow");
 			shader->heterogeneous_volume = !get_boolean(cmat, "homogeneous_volume");
 			shader->volume_sampling_method = RNA_enum_get(&cmat, "volume_sampling");
+			shader->volume_interpolation_method = RNA_enum_get(&cmat, "volume_interpolation");
 
 			shader->set_graph(graph);
 			shader->tag_update(scene);
@@ -1045,6 +1046,7 @@ void BlenderSync::sync_world(bool update_all)
 			PointerRNA cworld = RNA_pointer_get(&b_world.ptr, "cycles");
 			shader->heterogeneous_volume = !get_boolean(cworld, "homogeneous_volume");
 			shader->volume_sampling_method = RNA_enum_get(&cworld, "volume_sampling");
+			shader->volume_interpolation_method = RNA_enum_get(&cworld, "volume_interpolation");
 		}
 		else if(b_world) {
 			ShaderNode *closure, *out;