Sample as Lamp option for world shaders, to enable multiple importance sampling.

By default lighting from the world is computed solely with indirect light
sampling. However for more complex environment maps this can be too noisy, as
sampling the BSDF may not easily find the highlights in the environment map
image. By enabling this option, the world background will be sampled as a lamp,
with lighter parts automatically given more samples.

Map Resolution specifies the size of the importance map (res x res). Before
rendering starts, an importance map is generated by "baking" a grayscale image
from the world shader. This will then be used to determine which parts of the
background are light and so should receive more samples than darker parts.
Higher resolutions will result in more accurate sampling but take more setup
time and memory.

Patch by Mike Farnsworth, thanks!

2 files changed, 32 insertions, 0 deletions

diff --git a/intern/cycles/blender/addon/properties.py b/intern/cycles/blender/addon/properties.py
index 0a3cffd5071..46a49f52de0 100644
--- a/intern/cycles/blender/addon/properties.py
+++ b/intern/cycles/blender/addon/properties.py
@@ -155,6 +155,10 @@ class CyclesWorldSettings(bpy.types.PropertyGroup):
     @classmethod
     def register(cls):
         bpy.types.World.cycles = PointerProperty(type=cls, name="Cycles World Settings", description="Cycles world settings")
+        cls.sample_as_light = BoolProperty(name="Sample as Lamp", description="Use direct light sampling for the environment, enabling for non-solid colors is recommended",
+            default=False)
+        cls.sample_map_resolution = IntProperty(name="Map Resolution", description="Importance map size is resolution x resolution; higher values potentially produce less noise, at the cost of memory and speed",
+            default=256, min=4, max=8096)
 
     @classmethod
     def unregister(cls):
diff --git a/intern/cycles/blender/addon/ui.py b/intern/cycles/blender/addon/ui.py
index 70f38fa7e8c..67ff79a2037 100644
--- a/intern/cycles/blender/addon/ui.py
+++ b/intern/cycles/blender/addon/ui.py
@@ -453,10 +453,38 @@ class CyclesWorld_PT_surface(CyclesButtonsPanel, Panel):
         layout = self.layout
 
         world = context.world
+
         if not panel_node_draw(layout, world, 'OUTPUT_WORLD', 'Surface'):
             layout.prop(world, "horizon_color", text="Color")
 
 
+class CyclesWorld_PT_settings(CyclesButtonsPanel, Panel):
+    bl_label = "Settings"
+    bl_context = "world"
+    bl_options = {'DEFAULT_CLOSED'}
+
+    @classmethod
+    def poll(cls, context):
+        return context.world and CyclesButtonsPanel.poll(context)
+
+    def draw(self, context):
+        layout = self.layout
+
+        world = context.world
+        cworld = world.cycles
+
+        split = layout.split()
+        col = split.column()
+
+        col.prop(cworld, "sample_as_light")
+        row = col.row()
+        row.active = cworld.sample_as_light
+        row.prop(cworld, "sample_map_resolution")
+
+        col = split.column()
+        col.label()
+
+
 class CyclesWorld_PT_volume(CyclesButtonsPanel, Panel):
     bl_label = "Volume"
     bl_context = "world"