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.

8 files changed, 34 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;