From 48f9cf19afb06c4c2e370af51981ca0bd75f106a Mon Sep 17 00:00:00 2001
From: Skyth <19259897+blueskythlikesclouds@users.noreply.github.com>
Date: Tue, 2 Jun 2026 17:09:02 +0300
Subject: [PATCH] Put area light cluster iterations behind a spec constant.

---
 servers/rendering/renderer_rd/cluster_builder_rd.h           | 5 +++++
 .../forward_clustered/render_forward_clustered.cpp           | 4 ++++
 .../forward_clustered/scene_shader_forward_clustered.h       | 1 +
 .../shaders/forward_clustered/scene_forward_clustered.glsl   | 2 +-
 .../forward_clustered/scene_forward_clustered_inc.glsl       | 4 ++++
 5 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/servers/rendering/renderer_rd/cluster_builder_rd.h b/servers/rendering/renderer_rd/cluster_builder_rd.h
index 6c60253fef..49b039a997 100644
--- a/servers/rendering/renderer_rd/cluster_builder_rd.h
+++ b/servers/rendering/renderer_rd/cluster_builder_rd.h
@@ -415,6 +415,11 @@ public:
 		render_element_count++;
 	}
 
+	_FORCE_INLINE_ uint32_t get_cluster_count_by_type(ElementType p_element_type) const {
+		DEV_ASSERT(p_element_type < ELEMENT_TYPE_MAX);
+		return cluster_count_by_type[p_element_type];
+	}
+
 	void bake_cluster();
 	void debug(ElementType p_element);
 
diff --git a/servers/rendering/renderer_rd/forward_clustered/render_forward_clustered.cpp b/servers/rendering/renderer_rd/forward_clustered/render_forward_clustered.cpp
index 85b8847235..0edef2c31e 100644
--- a/servers/rendering/renderer_rd/forward_clustered/render_forward_clustered.cpp
+++ b/servers/rendering/renderer_rd/forward_clustered/render_forward_clustered.cpp
@@ -2181,6 +2181,10 @@ void RenderForwardClustered::_render_scene(RenderDataRD *p_render_data, const Co
 	}
 	_pre_opaque_render(p_render_data, using_ssao, using_ssil, using_ssr, using_sdfgi || using_voxelgi, normal_roughness_views, rb_data.is_valid() && rb_data->has_voxelgi() ? rb_data->get_voxelgi() : RID());
 
+	if (current_cluster_builder) {
+		base_specialization.cluster_has_area_light = current_cluster_builder->get_cluster_count_by_type(ClusterBuilderRD::ELEMENT_TYPE_AREA_LIGHT) != 0;
+	}
+
 	RENDER_TIMESTAMP("Render Opaque Pass");
 
 	RD::get_singleton()->draw_command_begin_label("Render Opaque Pass");
diff --git a/servers/rendering/renderer_rd/forward_clustered/scene_shader_forward_clustered.h b/servers/rendering/renderer_rd/forward_clustered/scene_shader_forward_clustered.h
index 1551213b7e..feb98ff4a6 100644
--- a/servers/rendering/renderer_rd/forward_clustered/scene_shader_forward_clustered.h
+++ b/servers/rendering/renderer_rd/forward_clustered/scene_shader_forward_clustered.h
@@ -127,6 +127,7 @@ public:
 				uint32_t multimesh_has_color : 1;
 				uint32_t multimesh_has_custom_data : 1;
 				uint32_t fog_use_legacy_blending : 1;
+				uint32_t cluster_has_area_light : 1;
 			};
 		};
 
diff --git a/servers/rendering/renderer_rd/shaders/forward_clustered/scene_forward_clustered.glsl b/servers/rendering/renderer_rd/shaders/forward_clustered/scene_forward_clustered.glsl
index 8eda7703bd..431f4800b9 100644
--- a/servers/rendering/renderer_rd/shaders/forward_clustered/scene_forward_clustered.glsl
+++ b/servers/rendering/renderer_rd/shaders/forward_clustered/scene_forward_clustered.glsl
@@ -2817,7 +2817,7 @@ void fragment_shader(in SceneData scene_data) {
 		}
 	}
 
-	{ // area lights
+	if (sc_cluster_has_area_light()) { // area lights
 
 		uint cluster_area_offset = cluster_offset + implementation_data.cluster_type_size * 2;
 
diff --git a/servers/rendering/renderer_rd/shaders/forward_clustered/scene_forward_clustered_inc.glsl b/servers/rendering/renderer_rd/shaders/forward_clustered/scene_forward_clustered_inc.glsl
index 81c4aefea4..4fc3ce2bc7 100644
--- a/servers/rendering/renderer_rd/shaders/forward_clustered/scene_forward_clustered_inc.glsl
+++ b/servers/rendering/renderer_rd/shaders/forward_clustered/scene_forward_clustered_inc.glsl
@@ -142,6 +142,10 @@ bool sc_fog_use_legacy_blending() {
 	return ((sc_packed_1() >> 4) & 1U) != 0;
 }
 
+bool sc_cluster_has_area_light() {
+	return ((sc_packed_1() >> 5) & 1U) != 0;
+}
+
 float sc_luminance_multiplier() {
 	// Not used in clustered renderer but we share some code with the mobile renderer that requires this.
 	return 1.0;