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.

1 files changed, 47 insertions, 42 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;
 					}
 				}
 			}