Add a per-light volumetric fog energy property

Per-light energy gives more control to the user on the final result of
volumetric fog. Specific lights can be fully excluded from volumetric fog
by setting their volumetric fog energy to 0, which improves performance
slightly. This can also be used to prevent short-lived dynamic effects
from poorly interacting with volumetric fog, as it's updated over several
frames by default unless temporal reprojection is disabled.

Volumetric fog shadows now obey Light3D's Shadow Opacity property as well.

The shadow fog fade property was removed as it had little visible impact
on the final scene's rendering.

2 files changed, 49 insertions, 44 deletions

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 6f79b9e771..07d5223472 100644
--- a/servers/rendering/renderer_rd/shaders/environment/volumetric_fog_process.glsl
+++ b/servers/rendering/renderer_rd/shaders/environment/volumetric_fog_process.glsl
@@ -270,6 +270,9 @@ const vec3 halton_map[TEMPORAL_FRAMES] = vec3[](
 		vec3(0.9375, 0.25925926, 0.12),
 		vec3(0.03125, 0.59259259, 0.32));
 
+// Higher values will make light in volumetric fog fade out sooner when it's occluded by shadow.
+const float INV_FOG_FADE = 10.0;
+
 void main() {
 	vec3 fog_cell_size = 1.0 / vec3(params.fog_volume_size);
 
@@ -375,46 +378,48 @@ void main() {
 
 	if (total_density > 0.001) {
 		for (uint i = 0; i < params.directional_light_count; i++) {
-			vec3 shadow_attenuation = vec3(1.0);
-
-			if (directional_lights.data[i].shadow_opacity > 0.001) {
-				float depth_z = -view_pos.z;
-
-				vec4 pssm_coord;
-				vec3 light_dir = directional_lights.data[i].direction;
-				vec4 v = vec4(view_pos, 1.0);
-				float z_range;
-
-				if (depth_z < directional_lights.data[i].shadow_split_offsets.x) {
-					pssm_coord = (directional_lights.data[i].shadow_matrix1 * v);
-					pssm_coord /= pssm_coord.w;
-					z_range = directional_lights.data[i].shadow_z_range.x;
-
-				} else if (depth_z < directional_lights.data[i].shadow_split_offsets.y) {
-					pssm_coord = (directional_lights.data[i].shadow_matrix2 * v);
-					pssm_coord /= pssm_coord.w;
-					z_range = directional_lights.data[i].shadow_z_range.y;
-
-				} else if (depth_z < directional_lights.data[i].shadow_split_offsets.z) {
-					pssm_coord = (directional_lights.data[i].shadow_matrix3 * v);
-					pssm_coord /= pssm_coord.w;
-					z_range = directional_lights.data[i].shadow_z_range.z;
-
-				} else {
-					pssm_coord = (directional_lights.data[i].shadow_matrix4 * v);
-					pssm_coord /= pssm_coord.w;
-					z_range = directional_lights.data[i].shadow_z_range.w;
-				}
+			if (directional_lights.data[i].volumetric_fog_energy > 0.001) {
+				vec3 shadow_attenuation = vec3(1.0);
+
+				if (directional_lights.data[i].shadow_opacity > 0.001) {
+					float depth_z = -view_pos.z;
+
+					vec4 pssm_coord;
+					vec3 light_dir = directional_lights.data[i].direction;
+					vec4 v = vec4(view_pos, 1.0);
+					float z_range;
+
+					if (depth_z < directional_lights.data[i].shadow_split_offsets.x) {
+						pssm_coord = (directional_lights.data[i].shadow_matrix1 * v);
+						pssm_coord /= pssm_coord.w;
+						z_range = directional_lights.data[i].shadow_z_range.x;
+
+					} else if (depth_z < directional_lights.data[i].shadow_split_offsets.y) {
+						pssm_coord = (directional_lights.data[i].shadow_matrix2 * v);
+						pssm_coord /= pssm_coord.w;
+						z_range = directional_lights.data[i].shadow_z_range.y;
+
+					} else if (depth_z < directional_lights.data[i].shadow_split_offsets.z) {
+						pssm_coord = (directional_lights.data[i].shadow_matrix3 * v);
+						pssm_coord /= pssm_coord.w;
+						z_range = directional_lights.data[i].shadow_z_range.z;
+
+					} else {
+						pssm_coord = (directional_lights.data[i].shadow_matrix4 * v);
+						pssm_coord /= pssm_coord.w;
+						z_range = directional_lights.data[i].shadow_z_range.w;
+					}
 
-				float depth = texture(sampler2D(directional_shadow_atlas, linear_sampler), pssm_coord.xy).r;
-				float shadow = exp(min(0.0, (depth - pssm_coord.z)) * z_range * directional_lights.data[i].shadow_volumetric_fog_fade);
+					float depth = texture(sampler2D(directional_shadow_atlas, linear_sampler), pssm_coord.xy).r;
+					float shadow = exp(min(0.0, (depth - pssm_coord.z)) * z_range * INV_FOG_FADE);
 
-				shadow = mix(shadow, 1.0, smoothstep(directional_lights.data[i].fade_from, directional_lights.data[i].fade_to, view_pos.z)); //done with negative values for performance
+					shadow = mix(shadow, 1.0, smoothstep(directional_lights.data[i].fade_from, directional_lights.data[i].fade_to, view_pos.z)); //done with negative values for performance
 
-				shadow_attenuation = mix(vec3(0.0), vec3(1.0), shadow);
-			}
+					shadow_attenuation = mix(vec3(1.0 - directional_lights.data[i].shadow_opacity), vec3(1.0), shadow);
+				}
 
-			total_light += shadow_attenuation * directional_lights.data[i].color * directional_lights.data[i].energy * henyey_greenstein(dot(normalize(view_pos), normalize(directional_lights.data[i].direction)), params.phase_g);
+				total_light += shadow_attenuation * directional_lights.data[i].color * directional_lights.data[i].energy * henyey_greenstein(dot(normalize(view_pos), normalize(directional_lights.data[i].direction)), params.phase_g) * directional_lights.data[i].volumetric_fog_energy;
+			}
 		}
 
 		// Compute light from sky
@@ -481,7 +486,7 @@ void main() {
 					float d = distance(omni_lights.data[light_index].position, view_pos);
 					float shadow_attenuation = 1.0;
 
-					if (d * omni_lights.data[light_index].inv_radius < 1.0) {
+					if (omni_lights.data[light_index].volumetric_fog_energy > 0.001 && d * omni_lights.data[light_index].inv_radius < 1.0) {
 						float attenuation = get_omni_attenuation(d, omni_lights.data[light_index].inv_radius, omni_lights.data[light_index].attenuation);
 
 						vec3 light = omni_lights.data[light_index].color;
@@ -509,9 +514,9 @@ void main() {
 
 							float depth = texture(sampler2D(shadow_atlas, linear_sampler), pos.xy).r;
 
-							shadow_attenuation = exp(min(0.0, (depth - pos.z)) / omni_lights.data[light_index].inv_radius * omni_lights.data[light_index].shadow_volumetric_fog_fade);
+							shadow_attenuation = mix(1.0 - omni_lights.data[light_index].shadow_opacity, 1.0, exp(min(0.0, (depth - pos.z)) / omni_lights.data[light_index].inv_radius * INV_FOG_FADE));
 						}
-						total_light += light * attenuation * shadow_attenuation * henyey_greenstein(dot(normalize(light_pos - view_pos), normalize(view_pos)), params.phase_g);
+						total_light += light * attenuation * shadow_attenuation * henyey_greenstein(dot(normalize(light_pos - view_pos), normalize(view_pos)), params.phase_g) * omni_lights.data[light_index].volumetric_fog_energy;
 					}
 				}
 			}
@@ -562,7 +567,7 @@ void main() {
 					float d = length(light_rel_vec);
 					float shadow_attenuation = 1.0;
 
-					if (d * spot_lights.data[light_index].inv_radius < 1.0) {
+					if (spot_lights.data[light_index].volumetric_fog_energy > 0.001 && d * spot_lights.data[light_index].inv_radius < 1.0) {
 						float attenuation = get_omni_attenuation(d, spot_lights.data[light_index].inv_radius, spot_lights.data[light_index].attenuation);
 
 						vec3 spot_dir = spot_lights.data[light_index].direction;
@@ -595,9 +600,9 @@ void main() {
 
 							float depth = texture(sampler2D(shadow_atlas, linear_sampler), pos.xy).r;
 
-							shadow_attenuation = exp(min(0.0, (depth - pos.z)) / spot_lights.data[light_index].inv_radius * spot_lights.data[light_index].shadow_volumetric_fog_fade);
+							shadow_attenuation = mix(1.0 - spot_lights.data[light_index].shadow_opacity, 1.0, exp(min(0.0, (depth - pos.z)) / spot_lights.data[light_index].inv_radius * INV_FOG_FADE));
 						}
-						total_light += light * attenuation * shadow_attenuation * henyey_greenstein(dot(normalize(light_rel_vec), normalize(view_pos)), params.phase_g);
+						total_light += light * attenuation * shadow_attenuation * henyey_greenstein(dot(normalize(light_rel_vec), normalize(view_pos)), params.phase_g) * spot_lights.data[light_index].volumetric_fog_energy;
 					}
 				}
 			}
diff --git a/servers/rendering/renderer_rd/shaders/light_data_inc.glsl b/servers/rendering/renderer_rd/shaders/light_data_inc.glsl
index 799f7087b6..a7fca25a6b 100644
--- a/servers/rendering/renderer_rd/shaders/light_data_inc.glsl
+++ b/servers/rendering/renderer_rd/shaders/light_data_inc.glsl
@@ -25,7 +25,7 @@ struct LightData { //this structure needs to be as packed as possible
 	highp float soft_shadow_size; // for spot, it's the size in uv coordinates of the light, for omni it's the span angle
 	highp float soft_shadow_scale; // scales the shadow kernel for blurrier shadows
 	uint mask;
-	mediump float shadow_volumetric_fog_fade;
+	mediump float volumetric_fog_energy;
 	uint bake_mode;
 	highp vec4 projector_rect; //projector rect in srgb decal atlas
 };
@@ -65,7 +65,7 @@ struct DirectionalLightData {
 	highp float fade_to;
 	uvec2 pad;
 	uint bake_mode;
-	mediump float shadow_volumetric_fog_fade;
+	mediump float volumetric_fog_energy;
 	highp vec4 shadow_bias;
 	highp vec4 shadow_normal_bias;
 	highp vec4 shadow_transmittance_bias;