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, 13 insertions, 0 deletions

diff --git a/source/blender/makesrna/intern/rna_lamp.c b/source/blender/makesrna/intern/rna_lamp.c
index 7828d4a7b7d..11a2c1a5529 100644
--- a/source/blender/makesrna/intern/rna_lamp.c
+++ b/source/blender/makesrna/intern/rna_lamp.c
@@ -164,6 +164,19 @@ static void rna_def_light(BlenderRNA *brna)
 	RNA_def_property_ui_text(prop, "Specular Factor", "Specular reflection multiplier");
 	RNA_def_property_update(prop, 0, "rna_Light_update");
 
+	prop = RNA_def_property(srna, "use_custom_distance", PROP_BOOLEAN, PROP_NONE);
+	RNA_def_property_boolean_sdna(prop, NULL, "mode", LA_CUSTOM_ATTENUATION);
+	RNA_def_property_ui_text(prop, "Custom Attenuation", "Use custom attenuation distance instead of global light threshold");
+	RNA_def_property_update(prop, 0, "rna_Light_update");
+
+	prop = RNA_def_property(srna, "cutoff_distance", PROP_FLOAT, PROP_DISTANCE);
+	RNA_def_property_float_sdna(prop, NULL, "att_dist");
+	RNA_def_property_float_default(prop, 1.0f);
+	RNA_def_property_range(prop, 0.0f, FLT_MAX);
+	RNA_def_property_ui_range(prop, 0.01f, 100.0f, 1.0, 2);
+	RNA_def_property_ui_text(prop, "Cutoff Distance", "Distance at which the light influence will be set to 0");
+	RNA_def_property_update(prop, 0, "rna_Light_update");
+
 	/* nodes */
 	prop = RNA_def_property(srna, "node_tree", PROP_POINTER, PROP_NONE);
 	RNA_def_property_pointer_sdna(prop, NULL, "nodetree");