Add a shadow opacity property to Light3D

This can be used to make shadows translucent for a specific light.

The light distance fade system also uses this to smoothly fade the shadow
when the light fade transition distance is greater than 0.

10 files changed, 36 insertions, 22 deletions

diff --git a/servers/rendering/renderer_rd/renderer_scene_render_rd.cpp b/servers/rendering/renderer_rd/renderer_scene_render_rd.cpp
index c6f38012a6..8b3b7050d2 100644
--- a/servers/rendering/renderer_rd/renderer_scene_render_rd.cpp
+++ b/servers/rendering/renderer_rd/renderer_scene_render_rd.cpp
@@ -2869,7 +2869,7 @@ void RendererSceneRenderRD::_setup_lights(const PagedArray<RID> &p_lights, const
 					WARN_PRINT_ONCE("The DirectionalLight3D PSSM splits debug draw mode is not reimplemented yet.");
 				}
 
-				light_data.shadow_enabled = p_using_shadows && light_storage->light_has_shadow(base);
+				light_data.shadow_opacity = p_using_shadows && light_storage->light_has_shadow(base) ? light_storage->light_get_param(base, RS::LIGHT_PARAM_SHADOW_OPACITY) : 0.0;
 
 				float angular_diameter = light_storage->light_get_param(base, RS::LIGHT_PARAM_SIZE);
 				if (angular_diameter > 0.0) {
@@ -2886,7 +2886,7 @@ void RendererSceneRenderRD::_setup_lights(const PagedArray<RID> &p_lights, const
 					angular_diameter = 0.0;
 				}
 
-				if (light_data.shadow_enabled) {
+				if (light_data.shadow_opacity > 0.001) {
 					RS::LightDirectionalShadowMode smode = light_storage->light_directional_get_shadow_mode(base);
 
 					int limit = smode == RS::LIGHT_DIRECTIONAL_SHADOW_ORTHOGONAL ? 0 : (smode == RS::LIGHT_DIRECTIONAL_SHADOW_PARALLEL_2_SPLITS ? 1 : 3);
@@ -3040,19 +3040,26 @@ void RendererSceneRenderRD::_setup_lights(const PagedArray<RID> &p_lights, const
 
 		// Reuse fade begin, fade length and distance for shadow LOD determination later.
 		float fade_begin = 0.0;
+		float fade_shadow = 0.0;
 		float fade_length = 0.0;
 		real_t distance = 0.0;
 
 		float fade = 1.0;
+		float shadow_opacity_fade = 1.0;
 		if (light_storage->light_is_distance_fade_enabled(li->light)) {
 			fade_begin = light_storage->light_get_distance_fade_begin(li->light);
+			fade_shadow = light_storage->light_get_distance_fade_shadow(li->light);
 			fade_length = light_storage->light_get_distance_fade_length(li->light);
 			distance = camera_plane.distance_to(li->transform.origin);
 
+			// Use `smoothstep()` to make opacity changes more gradual and less noticeable to the player.
 			if (distance > fade_begin) {
-				// Use `smoothstep()` to make opacity changes more gradual and less noticeable to the player.
 				fade = Math::smoothstep(0.0f, 1.0f, 1.0f - float(distance - fade_begin) / fade_length);
 			}
+
+			if (distance > fade_shadow) {
+				shadow_opacity_fade = Math::smoothstep(0.0f, 1.0f, 1.0f - float(distance - fade_shadow) / fade_length);
+			}
 		}
 
 		float energy = sign * light_storage->light_get_param(base, RS::LIGHT_PARAM_ENERGY) * Math_PI * fade;
@@ -3120,7 +3127,7 @@ void RendererSceneRenderRD::_setup_lights(const PagedArray<RID> &p_lights, const
 
 		bool in_shadow_range = true;
 		if (needs_shadow && light_storage->light_is_distance_fade_enabled(li->light)) {
-			if (distance > light_storage->light_get_distance_fade_shadow(li->light)) {
+			if (distance > light_storage->light_get_distance_fade_shadow(li->light) + light_storage->light_get_distance_fade_length(li->light)) {
 				// Out of range, don't draw shadows to improve performance.
 				in_shadow_range = false;
 			}
@@ -3129,7 +3136,7 @@ void RendererSceneRenderRD::_setup_lights(const PagedArray<RID> &p_lights, const
 		if (needs_shadow && in_shadow_range) {
 			// fill in the shadow information
 
-			light_data.shadow_enabled = true;
+			light_data.shadow_opacity = light_storage->light_get_param(base, RS::LIGHT_PARAM_SHADOW_OPACITY) * shadow_opacity_fade;
 
 			float shadow_texel_size = light_instance_get_shadow_texel_size(li->self, p_shadow_atlas);
 			light_data.shadow_normal_bias = light_storage->light_get_param(base, RS::LIGHT_PARAM_SHADOW_NORMAL_BIAS) * shadow_texel_size * 10.0;
@@ -3189,7 +3196,7 @@ void RendererSceneRenderRD::_setup_lights(const PagedArray<RID> &p_lights, const
 				}
 			}
 		} else {
-			light_data.shadow_enabled = false;
+			light_data.shadow_opacity = 0.0;
 		}
 
 		li->cull_mask = light_storage->light_get_cull_mask(base);
@@ -3637,7 +3644,7 @@ void RendererSceneRenderRD::_pre_opaque_render(RenderDataRD *p_render_data, bool
 	if (p_render_data->render_buffers.is_valid()) {
 		bool directional_shadows = false;
 		for (uint32_t i = 0; i < directional_light_count; i++) {
-			if (cluster.directional_lights[i].shadow_enabled) {
+			if (cluster.directional_lights[i].shadow_opacity > 0.001) {
 				directional_shadows = true;
 				break;
 			}
diff --git a/servers/rendering/renderer_rd/renderer_scene_render_rd.h b/servers/rendering/renderer_rd/renderer_scene_render_rd.h
index 09ec2a9efd..22e9ead243 100644
--- a/servers/rendering/renderer_rd/renderer_scene_render_rd.h
+++ b/servers/rendering/renderer_rd/renderer_scene_render_rd.h
@@ -608,7 +608,7 @@ private:
 			float inv_spot_attenuation;
 			float cos_spot_angle;
 			float specular_amount;
-			uint32_t shadow_enabled;
+			float shadow_opacity;
 
 			float atlas_rect[4]; // in omni, used for atlas uv, in spot, used for projector uv
 			float shadow_matrix[16];
@@ -633,7 +633,7 @@ private:
 			float softshadow_angle;
 			float soft_shadow_scale;
 			uint32_t blend_splits;
-			uint32_t shadow_enabled;
+			float shadow_opacity;
 			float fade_from;
 			float fade_to;
 			uint32_t pad[2];
diff --git a/servers/rendering/renderer_rd/shaders/environment/volumetric_fog_process.glsl b/servers/rendering/renderer_rd/shaders/environment/volumetric_fog_process.glsl
index e74cfad65c..6f79b9e771 100644
--- a/servers/rendering/renderer_rd/shaders/environment/volumetric_fog_process.glsl
+++ b/servers/rendering/renderer_rd/shaders/environment/volumetric_fog_process.glsl
@@ -377,7 +377,7 @@ void main() {
 		for (uint i = 0; i < params.directional_light_count; i++) {
 			vec3 shadow_attenuation = vec3(1.0);
 
-			if (directional_lights.data[i].shadow_enabled) {
+			if (directional_lights.data[i].shadow_opacity > 0.001) {
 				float depth_z = -view_pos.z;
 
 				vec4 pssm_coord;
@@ -486,7 +486,7 @@ void main() {
 
 						vec3 light = omni_lights.data[light_index].color;
 
-						if (omni_lights.data[light_index].shadow_enabled) {
+						if (omni_lights.data[light_index].shadow_opacity > 0.001) {
 							//has shadow
 							vec4 uv_rect = omni_lights.data[light_index].atlas_rect;
 							vec2 flip_offset = omni_lights.data[light_index].direction.xy;
@@ -572,7 +572,7 @@ void main() {
 
 						vec3 light = spot_lights.data[light_index].color;
 
-						if (spot_lights.data[light_index].shadow_enabled) {
+						if (spot_lights.data[light_index].shadow_opacity > 0.001) {
 							//has shadow
 							vec4 uv_rect = spot_lights.data[light_index].atlas_rect;
 							vec2 flip_offset = spot_lights.data[light_index].direction.xy;
diff --git a/servers/rendering/renderer_rd/shaders/light_data_inc.glsl b/servers/rendering/renderer_rd/shaders/light_data_inc.glsl
index 61c8488a05..799f7087b6 100644
--- a/servers/rendering/renderer_rd/shaders/light_data_inc.glsl
+++ b/servers/rendering/renderer_rd/shaders/light_data_inc.glsl
@@ -15,7 +15,7 @@ struct LightData { //this structure needs to be as packed as possible
 	mediump float cone_attenuation;
 	mediump float cone_angle;
 	mediump float specular_amount;
-	bool shadow_enabled;
+	mediump float shadow_opacity;
 
 	highp vec4 atlas_rect; // rect in the shadow atlas
 	highp mat4 shadow_matrix;
@@ -60,7 +60,7 @@ struct DirectionalLightData {
 	highp float softshadow_angle;
 	highp float soft_shadow_scale;
 	bool blend_splits;
-	bool shadow_enabled;
+	mediump float shadow_opacity;
 	highp float fade_from;
 	highp float fade_to;
 	uvec2 pad;
diff --git a/servers/rendering/renderer_rd/shaders/scene_forward_clustered.glsl b/servers/rendering/renderer_rd/shaders/scene_forward_clustered.glsl
index 22058b3a06..dff24b7144 100644
--- a/servers/rendering/renderer_rd/shaders/scene_forward_clustered.glsl
+++ b/servers/rendering/renderer_rd/shaders/scene_forward_clustered.glsl
@@ -1417,7 +1417,7 @@ void fragment_shader(in SceneData scene_data) {
 
 			float shadow = 1.0;
 
-			if (directional_lights.data[i].shadow_enabled) {
+			if (directional_lights.data[i].shadow_opacity > 0.001) {
 				float depth_z = -vertex.z;
 				vec3 light_dir = directional_lights.data[i].direction;
 				vec3 base_normal_bias = normalize(normal_interp) * (1.0 - max(0.0, dot(light_dir, -normalize(normal_interp))));
@@ -1626,7 +1626,7 @@ void fragment_shader(in SceneData scene_data) {
 #ifdef LIGHT_TRANSMITTANCE_USED
 			float transmittance_z = transmittance_depth;
 
-			if (directional_lights.data[i].shadow_enabled) {
+			if (directional_lights.data[i].shadow_opacity > 0.001) {
 				float depth_z = -vertex.z;
 
 				if (depth_z < directional_lights.data[i].shadow_split_offsets.x) {
@@ -1681,6 +1681,8 @@ void fragment_shader(in SceneData scene_data) {
 			} else {
 				shadow = float(shadow1 >> ((i - 4) * 8) & 0xFF) / 255.0;
 			}
+
+			shadow = shadow * directional_lights.data[i].shadow_opacity + 1.0 - directional_lights.data[i].shadow_opacity;
 #endif
 
 			blur_shadow(shadow);
diff --git a/servers/rendering/renderer_rd/shaders/scene_forward_lights_inc.glsl b/servers/rendering/renderer_rd/shaders/scene_forward_lights_inc.glsl
index e27c81eaea..50a13de11a 100644
--- a/servers/rendering/renderer_rd/shaders/scene_forward_lights_inc.glsl
+++ b/servers/rendering/renderer_rd/shaders/scene_forward_lights_inc.glsl
@@ -395,7 +395,7 @@ float get_omni_attenuation(float distance, float inv_range, float decay) {
 
 float light_process_omni_shadow(uint idx, vec3 vertex, vec3 normal) {
 #ifndef SHADOWS_DISABLED
-	if (omni_lights.data[idx].shadow_enabled) {
+	if (omni_lights.data[idx].shadow_opacity > 0.001) {
 		// there is a shadowmap
 		vec2 texel_size = scene_data_block.data.shadow_atlas_pixel_size;
 		vec4 base_uv_rect = omni_lights.data[idx].atlas_rect;
@@ -498,6 +498,7 @@ float light_process_omni_shadow(uint idx, vec3 vertex, vec3 normal) {
 				}
 
 				shadow /= float(sc_penumbra_shadow_samples);
+				shadow = mix(1.0, shadow, omni_lights.data[idx].shadow_opacity);
 
 			} else {
 				//no blockers found, so no shadow
@@ -516,7 +517,7 @@ float light_process_omni_shadow(uint idx, vec3 vertex, vec3 normal) {
 			vec2 pos = shadow_sample.xy / shadow_sample.z;
 			float depth = shadow_len - omni_lights.data[idx].shadow_bias;
 			depth *= omni_lights.data[idx].inv_radius;
-			shadow = sample_omni_pcf_shadow(shadow_atlas, omni_lights.data[idx].soft_shadow_scale / shadow_sample.z, pos, uv_rect, flip_offset, depth);
+			shadow = mix(1.0, sample_omni_pcf_shadow(shadow_atlas, omni_lights.data[idx].soft_shadow_scale / shadow_sample.z, pos, uv_rect, flip_offset, depth), omni_lights.data[idx].shadow_opacity);
 		}
 
 		return shadow;
@@ -674,7 +675,7 @@ void light_process_omni(uint idx, vec3 vertex, vec3 eye_vec, vec3 normal, vec3 v
 
 float light_process_spot_shadow(uint idx, vec3 vertex, vec3 normal) {
 #ifndef SHADOWS_DISABLED
-	if (spot_lights.data[idx].shadow_enabled) {
+	if (spot_lights.data[idx].shadow_opacity > 0.001) {
 		vec3 light_rel_vec = spot_lights.data[idx].position - vertex;
 		float light_length = length(light_rel_vec);
 		vec3 spot_dir = spot_lights.data[idx].direction;
@@ -735,6 +736,7 @@ float light_process_spot_shadow(uint idx, vec3 vertex, vec3 normal) {
 				}
 
 				shadow /= float(sc_penumbra_shadow_samples);
+				shadow = mix(1.0, shadow, spot_lights.data[idx].shadow_opacity);
 
 			} else {
 				//no blockers found, so no shadow
@@ -743,7 +745,7 @@ float light_process_spot_shadow(uint idx, vec3 vertex, vec3 normal) {
 		} else {
 			//hard shadow
 			vec3 shadow_uv = vec3(splane.xy * spot_lights.data[idx].atlas_rect.zw + spot_lights.data[idx].atlas_rect.xy, splane.z);
-			shadow = sample_pcf_shadow(shadow_atlas, spot_lights.data[idx].soft_shadow_scale * scene_data_block.data.shadow_atlas_pixel_size, shadow_uv);
+			shadow = mix(1.0, sample_pcf_shadow(shadow_atlas, spot_lights.data[idx].soft_shadow_scale * scene_data_block.data.shadow_atlas_pixel_size, shadow_uv), spot_lights.data[idx].shadow_opacity);
 		}
 
 		return shadow;
diff --git a/servers/rendering/renderer_rd/shaders/scene_forward_mobile.glsl b/servers/rendering/renderer_rd/shaders/scene_forward_mobile.glsl
index 26d0de46c2..eb73a33558 100644
--- a/servers/rendering/renderer_rd/shaders/scene_forward_mobile.glsl
+++ b/servers/rendering/renderer_rd/shaders/scene_forward_mobile.glsl
@@ -1134,7 +1134,7 @@ void main() {
 
 #ifdef USE_SOFT_SHADOWS
 			//version with soft shadows, more expensive
-			if (directional_lights.data[i].shadow_enabled) {
+			if (directional_lights.data[i].shadow_opacity > 0.001) {
 				float depth_z = -vertex.z;
 
 				vec4 pssm_coord;
@@ -1286,7 +1286,7 @@ void main() {
 #else
 			// Soft shadow disabled version
 
-			if (directional_lights.data[i].shadow_enabled) {
+			if (directional_lights.data[i].shadow_opacity > 0.001) {
 				float depth_z = -vertex.z;
 
 				vec4 pssm_coord;
diff --git a/servers/rendering/renderer_rd/storage_rd/light_storage.cpp b/servers/rendering/renderer_rd/storage_rd/light_storage.cpp
index d3831b4618..882afdfa54 100644
--- a/servers/rendering/renderer_rd/storage_rd/light_storage.cpp
+++ b/servers/rendering/renderer_rd/storage_rd/light_storage.cpp
@@ -88,6 +88,7 @@ void LightStorage::_light_initialize(RID p_light, RS::LightType p_type) {
 	light.param[RS::LIGHT_PARAM_SHADOW_FADE_START] = 0.8;
 	light.param[RS::LIGHT_PARAM_SHADOW_NORMAL_BIAS] = 1.0;
 	light.param[RS::LIGHT_PARAM_SHADOW_BIAS] = 0.02;
+	light.param[RS::LIGHT_PARAM_SHADOW_OPACITY] = 1.0;
 	light.param[RS::LIGHT_PARAM_SHADOW_BLUR] = 0;
 	light.param[RS::LIGHT_PARAM_SHADOW_PANCAKE_SIZE] = 20.0;
 	light.param[RS::LIGHT_PARAM_SHADOW_VOLUMETRIC_FOG_FADE] = 0.1;
diff --git a/servers/rendering_server.cpp b/servers/rendering_server.cpp
index 1ac9b5854d..a54d4f0384 100644
--- a/servers/rendering_server.cpp
+++ b/servers/rendering_server.cpp
@@ -1911,6 +1911,7 @@ void RenderingServer::_bind_methods() {
 	BIND_ENUM_CONSTANT(LIGHT_PARAM_SHADOW_NORMAL_BIAS);
 	BIND_ENUM_CONSTANT(LIGHT_PARAM_SHADOW_BIAS);
 	BIND_ENUM_CONSTANT(LIGHT_PARAM_SHADOW_PANCAKE_SIZE);
+	BIND_ENUM_CONSTANT(LIGHT_PARAM_SHADOW_OPACITY);
 	BIND_ENUM_CONSTANT(LIGHT_PARAM_SHADOW_BLUR);
 	BIND_ENUM_CONSTANT(LIGHT_PARAM_SHADOW_VOLUMETRIC_FOG_FADE);
 	BIND_ENUM_CONSTANT(LIGHT_PARAM_TRANSMITTANCE_BIAS);
diff --git a/servers/rendering_server.h b/servers/rendering_server.h
index 297736aec7..a2fe9caf19 100644
--- a/servers/rendering_server.h
+++ b/servers/rendering_server.h
@@ -425,6 +425,7 @@ public:
 		LIGHT_PARAM_SHADOW_NORMAL_BIAS,
 		LIGHT_PARAM_SHADOW_BIAS,
 		LIGHT_PARAM_SHADOW_PANCAKE_SIZE,
+		LIGHT_PARAM_SHADOW_OPACITY,
 		LIGHT_PARAM_SHADOW_BLUR,
 		LIGHT_PARAM_SHADOW_VOLUMETRIC_FOG_FADE,
 		LIGHT_PARAM_TRANSMITTANCE_BIAS,