Cycles: Add Volume Direct and Volume Indirect passes for volume-scattered light

No color pass because it's hard to define what to use as color in a volume.

Reviewers: sergey, brecht

Differential Revision: https://developer.blender.org/D2903

4 files changed, 32 insertions, 4 deletions

diff --git a/intern/cycles/blender/addon/engine.py b/intern/cycles/blender/addon/engine.py
index 3018fd5b316..bc71a1b2fd7 100644
--- a/intern/cycles/blender/addon/engine.py
+++ b/intern/cycles/blender/addon/engine.py
@@ -234,10 +234,12 @@ def register_passes(engine, scene, srl):
     if srl.use_pass_environment:           engine.register_pass(scene, srl, "Env",           3, "RGB",  'COLOR')
 
     crl = srl.cycles
-    if crl.pass_debug_bvh_traversed_nodes:     engine.register_pass(scene, srl, "Debug BVH Traversed Nodes",     1, "X", 'VALUE')
-    if crl.pass_debug_bvh_traversed_instances: engine.register_pass(scene, srl, "Debug BVH Traversed Instances", 1, "X", 'VALUE')
-    if crl.pass_debug_bvh_intersections:       engine.register_pass(scene, srl, "Debug BVH Intersections",       1, "X", 'VALUE')
-    if crl.pass_debug_ray_bounces:             engine.register_pass(scene, srl, "Debug Ray Bounces",             1, "X", 'VALUE')
+    if crl.pass_debug_bvh_traversed_nodes:     engine.register_pass(scene, srl, "Debug BVH Traversed Nodes",     1, "X",   'VALUE')
+    if crl.pass_debug_bvh_traversed_instances: engine.register_pass(scene, srl, "Debug BVH Traversed Instances", 1, "X",   'VALUE')
+    if crl.pass_debug_bvh_intersections:       engine.register_pass(scene, srl, "Debug BVH Intersections",       1, "X",   'VALUE')
+    if crl.pass_debug_ray_bounces:             engine.register_pass(scene, srl, "Debug Ray Bounces",             1, "X",   'VALUE')
+    if crl.use_pass_volume_direct:             engine.register_pass(scene, srl, "VolumeDir",                     3, "RGB", 'COLOR')
+    if crl.use_pass_volume_indirect:           engine.register_pass(scene, srl, "VolumeInd",                     3, "RGB", 'COLOR')
 
     cscene = scene.cycles
     if crl.use_denoising and crl.denoising_store_passes and not cscene.use_progressive_refine:
diff --git a/intern/cycles/blender/addon/properties.py b/intern/cycles/blender/addon/properties.py
index 2e149527066..e20e0b757c1 100644
--- a/intern/cycles/blender/addon/properties.py
+++ b/intern/cycles/blender/addon/properties.py
@@ -1189,6 +1189,18 @@ class CyclesRenderLayerSettings(bpy.types.PropertyGroup):
                 default=False,
                 update=update_render_passes,
                 )
+        cls.use_pass_volume_direct = BoolProperty(
+                name="Volume Direct",
+                description="Deliver direct volumetric scattering pass",
+                default=False,
+                update=update_render_passes,
+                )
+        cls.use_pass_volume_indirect = BoolProperty(
+                name="Volume Indirect",
+                description="Deliver indirect volumetric scattering pass",
+                default=False,
+                update=update_render_passes,
+                )
 
         cls.use_denoising = BoolProperty(
                 name="Use Denoising",
diff --git a/intern/cycles/blender/addon/ui.py b/intern/cycles/blender/addon/ui.py
index 67f1029acb9..ff36e2a82d8 100644
--- a/intern/cycles/blender/addon/ui.py
+++ b/intern/cycles/blender/addon/ui.py
@@ -526,6 +526,10 @@ class CYCLES_RENDER_PT_layer_passes(CyclesButtonsPanel, Panel):
         row.prop(rl, "use_pass_subsurface_direct", text="Direct", toggle=True)
         row.prop(rl, "use_pass_subsurface_indirect", text="Indirect", toggle=True)
         row.prop(rl, "use_pass_subsurface_color", text="Color", toggle=True)
+        col.label(text="Volume:")
+        row = col.row(align=True)
+        row.prop(crl, "use_pass_volume_direct", text="Direct", toggle=True)
+        row.prop(crl, "use_pass_volume_indirect", text="Indirect", toggle=True)
 
         col.separator()
         col.prop(rl, "use_pass_emit", text="Emission")
diff --git a/intern/cycles/blender/blender_sync.cpp b/intern/cycles/blender/blender_sync.cpp
index 142fd5ef85b..dbc559e749e 100644
--- a/intern/cycles/blender/blender_sync.cpp
+++ b/intern/cycles/blender/blender_sync.cpp
@@ -496,11 +496,13 @@ PassType BlenderSync::get_pass_type(BL::RenderPass& b_pass)
 	MAP_PASS("GlossDir", PASS_GLOSSY_DIRECT);
 	MAP_PASS("TransDir", PASS_TRANSMISSION_DIRECT);
 	MAP_PASS("SubsurfaceDir", PASS_SUBSURFACE_DIRECT);
+	MAP_PASS("VolumeDir", PASS_VOLUME_DIRECT);
 
 	MAP_PASS("DiffInd", PASS_DIFFUSE_INDIRECT);
 	MAP_PASS("GlossInd", PASS_GLOSSY_INDIRECT);
 	MAP_PASS("TransInd", PASS_TRANSMISSION_INDIRECT);
 	MAP_PASS("SubsurfaceInd", PASS_SUBSURFACE_INDIRECT);
+	MAP_PASS("VolumeInd", PASS_VOLUME_INDIRECT);
 
 	MAP_PASS("DiffCol", PASS_DIFFUSE_COLOR);
 	MAP_PASS("GlossCol", PASS_GLOSSY_COLOR);
@@ -604,6 +606,14 @@ array<Pass> BlenderSync::sync_render_passes(BL::RenderLayer& b_rlay,
 		Pass::add(PASS_RAY_BOUNCES, passes);
 	}
 #endif
+	if(get_boolean(crp, "use_pass_volume_direct")) {
+		b_engine.add_pass("VolumeDir", 3, "RGB", b_srlay.name().c_str());
+		Pass::add(PASS_VOLUME_DIRECT, passes);
+	}
+	if(get_boolean(crp, "use_pass_volume_indirect")) {
+		b_engine.add_pass("VolumeInd", 3, "RGB", b_srlay.name().c_str());
+		Pass::add(PASS_VOLUME_INDIRECT, passes);
+	}
 
 	return passes;
 }