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, 7 insertions, 0 deletions

diff --git a/source/blender/makesrna/intern/rna_scene.c b/source/blender/makesrna/intern/rna_scene.c
index 17513a55e23..123ed562343 100644
--- a/source/blender/makesrna/intern/rna_scene.c
+++ b/source/blender/makesrna/intern/rna_scene.c
@@ -6035,6 +6035,13 @@ static void rna_def_scene_eevee(BlenderRNA *brna)
 	RNA_def_property_ui_text(prop, "Soft Shadows", "Randomize shadowmaps origin to create soft shadows");
 	RNA_def_property_override_flag(prop, PROPOVERRIDE_OVERRIDABLE_STATIC);
 
+	prop = RNA_def_property(srna, "light_threshold", PROP_FLOAT, PROP_UNSIGNED);
+	RNA_def_property_float_default(prop, 0.01f);
+	RNA_def_property_ui_text(prop, "Light Threshold", "Minimum light intensity for a light to contribute to the lighting");
+	RNA_def_property_range(prop, 0.0f, FLT_MAX);
+	RNA_def_property_ui_range(prop, 0.0f, 1.0f, 0.1, 3);
+	RNA_def_property_override_flag(prop, PROPOVERRIDE_OVERRIDABLE_STATIC);
+
 	/* Overscan */
 	prop = RNA_def_property(srna, "use_overscan", PROP_BOOLEAN, PROP_NONE);
 	RNA_def_property_boolean_sdna(prop, NULL, "flag", SCE_EEVEE_OVERSCAN);