Improve performance of shader lighting code in Forward renderers.

- Skip sampling shadows if attenuation is very small.
- Skip computing diffuse and specular light if attenuation and shadow are very small.

Author: DarioSamo

servers/rendering/renderer_rd/shaders/forward_clustered/scene_forward_clustered.glsl

@@ -2369,11 +2369,7 @@ void fragment_shader(in SceneData scene_data) {
 					continue; // Statically baked light and object uses lightmap, skip
 				}
 
-				float shadow = light_process_omni_shadow(light_index, vertex, normal, scene_data.taa_frame_count);
-
-				shadow = blur_shadow(shadow);
-
-				light_process_omni(light_index, vertex, view, normal, vertex_ddx, vertex_ddy, f0, orms, shadow, albedo, alpha, screen_uv,
+				light_process_omni(light_index, vertex, view, normal, vertex_ddx, vertex_ddy, f0, orms, scene_data.taa_frame_count, albedo, alpha, screen_uv,
 #ifdef LIGHT_BACKLIGHT_USED
 						backlight,
 #endif
@@ -2441,11 +2437,7 @@ void fragment_shader(in SceneData scene_data) {
 					continue; // Statically baked light and object uses lightmap, skip
 				}
 
-				float shadow = light_process_spot_shadow(light_index, vertex, normal, scene_data.taa_frame_count);
-
-				shadow = blur_shadow(shadow);
-
-				light_process_spot(light_index, vertex, view, normal, vertex_ddx, vertex_ddy, f0, orms, shadow, albedo, alpha, screen_uv,
+				light_process_spot(light_index, vertex, view, normal, vertex_ddx, vertex_ddy, f0, orms, scene_data.taa_frame_count, albedo, alpha, screen_uv,
 #ifdef LIGHT_BACKLIGHT_USED
 						backlight,
 #endif

servers/rendering/renderer_rd/shaders/forward_mobile/scene_forward_mobile.glsl

@@ -1622,13 +1622,7 @@ void main() {
 	uvec2 omni_indices = instances.data[draw_call.instance_index].omni_lights;
 	for (uint i = 0; i < sc_omni_lights(); i++) {
 		uint light_index = (i > 3) ? ((omni_indices.y >> ((i - 4) * 8)) & 0xFF) : ((omni_indices.x >> (i * 8)) & 0xFF);
-
-		float shadow = light_process_omni_shadow(light_index, vertex, normal, scene_data.taa_frame_count);
-
-		shadow = blur_shadow(shadow);
-
-		// Fragment lighting
-		light_process_omni(light_index, vertex, view, normal, vertex_ddx, vertex_ddy, f0, orms, shadow, albedo, alpha, screen_uv,
+		light_process_omni(light_index, vertex, view, normal, vertex_ddx, vertex_ddy, f0, orms, scene_data.taa_frame_count, albedo, alpha, screen_uv,
 #ifdef LIGHT_BACKLIGHT_USED
 				backlight,
 #endif
@@ -1656,12 +1650,7 @@ void main() {
 	uvec2 spot_indices = instances.data[draw_call.instance_index].spot_lights;
 	for (uint i = 0; i < sc_spot_lights(); i++) {
 		uint light_index = (i > 3) ? ((spot_indices.y >> ((i - 4) * 8)) & 0xFF) : ((spot_indices.x >> (i * 8)) & 0xFF);
-
-		float shadow = light_process_spot_shadow(light_index, vertex, normal, scene_data.taa_frame_count);
-
-		shadow = blur_shadow(shadow);
-
-		light_process_spot(light_index, vertex, view, normal, vertex_ddx, vertex_ddy, f0, orms, shadow, albedo, alpha, screen_uv,
+		light_process_spot(light_index, vertex, view, normal, vertex_ddx, vertex_ddy, f0, orms, scene_data.taa_frame_count, albedo, alpha, screen_uv,
 #ifdef LIGHT_BACKLIGHT_USED
 				backlight,
 #endif