Eevee: Add Light Threshold value

This is an important change. Starting from now, all lights have a finite
influence radius (similar to the old sphere option for BI).

In order to avoid costly setup time, this distance is first computed
automatically based on a light threshold. The distance is computed
at the light origin and using the inverse square falloff. The setting
can be found inside the render settings panel > shadow tab.

This light threshold does not take the light shape into account an may not
suit every case. That's why we provide a per lamp override where you can
just set the cutt off distance (Light Properties Panel > Light >
Custom Distance).

The influence distance is also used as shadow far clip distance.

This influence distance does not concerns sun lights that still have a
far clip distance.

---

This change is important because it makes it possible to cull lights
an improve performance drastically in the future.

1 files changed, 33 insertions, 1 deletions

diff --git a/release/scripts/startup/bl_ui/properties_data_light.py b/release/scripts/startup/bl_ui/properties_data_light.py
index 8aa70d1e05f..7d21ecb99b3 100644
--- a/release/scripts/startup/bl_ui/properties_data_light.py
+++ b/release/scripts/startup/bl_ui/properties_data_light.py
@@ -105,6 +105,36 @@ class DATA_PT_EEVEE_light(DataButtonsPanel, Panel):
                 sub.prop(light, "size_y", text="Y")
 
 
+class DATA_PT_EEVEE_light_distance(DataButtonsPanel, Panel):
+    bl_label = "Custom Distance"
+    bl_parent_id = "DATA_PT_EEVEE_light"
+    bl_options = {'DEFAULT_CLOSED'}
+    COMPAT_ENGINES = {'BLENDER_EEVEE'}
+
+    @classmethod
+    def poll(cls, context):
+        light = context.light
+        engine = context.engine
+
+        return (light and light.type != 'SUN') and (engine in cls.COMPAT_ENGINES)
+
+    def draw_header(self, context):
+        light = context.light
+
+        layout = self.layout
+        layout.active = light.use_shadow
+        layout.prop(light, "use_custom_distance", text="")
+
+    def draw(self, context):
+        layout = self.layout
+        light = context.light
+        layout.use_property_split = True
+
+        col = layout.column()
+
+        col.prop(light, "cutoff_distance", text="Distance")
+
+
 class DATA_PT_EEVEE_shadow(DataButtonsPanel, Panel):
     bl_label = "Shadow"
     bl_options = {'DEFAULT_CLOSED'}
@@ -131,7 +161,8 @@ class DATA_PT_EEVEE_shadow(DataButtonsPanel, Panel):
         col = layout.column()
         sub = col.column(align=True)
         sub.prop(light, "shadow_buffer_clip_start", text="Clip Start")
-        sub.prop(light, "shadow_buffer_clip_end", text="End")
+        if light.type == 'SUN':
+            sub.prop(light, "shadow_buffer_clip_end", text="End")
 
         col.prop(light, "shadow_buffer_soft", text="Softness")
 
@@ -281,6 +312,7 @@ classes = (
     DATA_PT_preview,
     DATA_PT_light,
     DATA_PT_EEVEE_light,
+    DATA_PT_EEVEE_light_distance,
     DATA_PT_EEVEE_shadow,
     DATA_PT_EEVEE_shadow_contact,
     DATA_PT_EEVEE_shadow_cascaded_shadow_map,