Various fixes for transmittance effect

Use correct shadow sampling for omni and spot lights

Disable transmittance if shadows are disabled

Correct DirectionalLight transmittance bias to match shadow bias (its still pretty sensitive though)

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

@@ -1983,7 +1983,7 @@ void fragment_shader(in SceneData scene_data) {
 
 #ifdef LIGHT_TRANSMITTANCE_USED
 			float transmittance_z = transmittance_depth;
-
+#ifndef SHADOWS_DISABLED
 			if (directional_lights.data[i].shadow_opacity > 0.001) {
 				float depth_z = -vertex.z;
 
@@ -2030,7 +2030,8 @@ void fragment_shader(in SceneData scene_data) {
 					transmittance_z = z - shadow_z;
 				}
 			}
-#endif
+#endif // !SHADOWS_DISABLED
+#endif // LIGHT_TRANSMITTANCE_USED
 
 			float shadow = 1.0;
 #ifndef SHADOWS_DISABLED

servers/rendering/renderer_rd/shaders/scene_forward_lights_inc.glsl

@@ -582,34 +582,39 @@ void light_process_omni(uint idx, vec3 vertex, vec3 eye_vec, vec3 normal, vec3 v
 #ifdef LIGHT_TRANSMITTANCE_USED
 	float transmittance_z = transmittance_depth; //no transmittance by default
 	transmittance_color.a *= light_attenuation;
-	{
-		vec4 clamp_rect = omni_lights.data[idx].atlas_rect;
+#ifndef SHADOWS_DISABLED
+	if (omni_lights.data[idx].shadow_opacity > 0.001) {
+		// Redo shadowmapping, but shrink the model a bit to avoid artifacts.
+		vec2 texel_size = scene_data_block.data.shadow_atlas_pixel_size;
+		vec4 uv_rect = omni_lights.data[idx].atlas_rect;
+		uv_rect.xy += texel_size;
+		uv_rect.zw -= texel_size * 2.0;
 
-		//redo shadowmapping, but shrink the model a bit to avoid artifacts
-		vec4 splane = (omni_lights.data[idx].shadow_matrix * vec4(vertex - normalize(normal_interp) * omni_lights.data[idx].transmittance_bias, 1.0));
+		// Omni lights use direction.xy to store to store the offset between the two paraboloid regions
+		vec2 flip_offset = omni_lights.data[idx].direction.xy;
 
-		float shadow_len = length(splane.xyz);
-		splane.xyz = normalize(splane.xyz);
+		vec3 local_vert = (omni_lights.data[idx].shadow_matrix * vec4(vertex - normalize(normal) * omni_lights.data[idx].transmittance_bias, 1.0)).xyz;
 
-		if (splane.z >= 0.0) {
-			splane.z += 1.0;
-			clamp_rect.y += clamp_rect.w;
-		} else {
-			splane.z = 1.0 - splane.z;
-		}
+		float shadow_len = length(local_vert); //need to remember shadow len from here
+		vec3 shadow_sample = normalize(local_vert);
 
-		splane.xy /= splane.z;
+		if (shadow_sample.z >= 0.0) {
+			uv_rect.xy += flip_offset;
+			flip_offset *= -1.0;
+		}
 
-		splane.xy = splane.xy * 0.5 + 0.5;
-		splane.z = shadow_len * omni_lights.data[idx].inv_radius;
-		splane.xy = clamp_rect.xy + splane.xy * clamp_rect.zw;
-		//		splane.xy = clamp(splane.xy,clamp_rect.xy + scene_data_block.data.shadow_atlas_pixel_size,clamp_rect.xy + clamp_rect.zw - scene_data_block.data.shadow_atlas_pixel_size );
-		splane.w = 1.0; //needed? i think it should be 1 already
+		shadow_sample.z = 1.0 + abs(shadow_sample.z);
+		vec2 pos = shadow_sample.xy / shadow_sample.z;
+		float depth = shadow_len * omni_lights.data[idx].inv_radius;
+		depth = 1.0 - depth;
 
-		float shadow_z = textureLod(sampler2D(shadow_atlas, SAMPLER_LINEAR_CLAMP), splane.xy, 0.0).r;
-		transmittance_z = (splane.z - shadow_z) / omni_lights.data[idx].inv_radius;
+		pos = pos * 0.5 + 0.5;
+		pos = uv_rect.xy + pos * uv_rect.zw;
+		float shadow_z = textureLod(sampler2D(shadow_atlas, SAMPLER_LINEAR_CLAMP), pos, 0.0).r;
+		transmittance_z = (depth - shadow_z) / omni_lights.data[idx].inv_radius;
 	}
-#endif
+#endif // !SHADOWS_DISABLED
+#endif // LIGHT_TRANSMITTANCE_USED
 
 	if (sc_use_light_projector && omni_lights.data[idx].projector_rect != vec4(0.0)) {
 		vec3 local_v = (omni_lights.data[idx].shadow_matrix * vec4(vertex, 1.0)).xyz;
@@ -834,12 +839,13 @@ void light_process_spot(uint idx, vec3 vertex, vec3 eye_vec, vec3 normal, vec3 v
 #ifdef LIGHT_TRANSMITTANCE_USED
 	float transmittance_z = transmittance_depth;
 	transmittance_color.a *= light_attenuation;
-	{
-		vec4 splane = (spot_lights.data[idx].shadow_matrix * vec4(vertex - normalize(normal_interp) * spot_lights.data[idx].transmittance_bias, 1.0));
+#ifndef SHADOWS_DISABLED
+	if (spot_lights.data[idx].shadow_opacity > 0.001) {
+		vec4 splane = (spot_lights.data[idx].shadow_matrix * vec4(vertex - normalize(normal) * spot_lights.data[idx].transmittance_bias, 1.0));
 		splane /= splane.w;
-		splane.xy = splane.xy * spot_lights.data[idx].atlas_rect.zw + spot_lights.data[idx].atlas_rect.xy;
 
-		float shadow_z = textureLod(sampler2D(shadow_atlas, SAMPLER_LINEAR_CLAMP), splane.xy, 0.0).r;
+		vec3 shadow_uv = vec3(splane.xy * spot_lights.data[idx].atlas_rect.zw + spot_lights.data[idx].atlas_rect.xy, splane.z);
+		float shadow_z = textureLod(sampler2D(shadow_atlas, SAMPLER_LINEAR_CLAMP), shadow_uv.xy, 0.0).r;
 
 		shadow_z = shadow_z * 2.0 - 1.0;
 		float z_far = 1.0 / spot_lights.data[idx].inv_radius;
@@ -850,7 +856,8 @@ void light_process_spot(uint idx, vec3 vertex, vec3 eye_vec, vec3 normal, vec3 v
 		float z = dot(spot_dir, -light_rel_vec);
 		transmittance_z = z - shadow_z;
 	}
-#endif //LIGHT_TRANSMITTANCE_USED
+#endif // !SHADOWS_DISABLED
+#endif // LIGHT_TRANSMITTANCE_USED
 
 	if (sc_use_light_projector && spot_lights.data[idx].projector_rect != vec4(0.0)) {
 		vec4 splane = (spot_lights.data[idx].shadow_matrix * vec4(vertex, 1.0));

servers/rendering/renderer_rd/storage_rd/light_storage.cpp

@@ -685,7 +685,7 @@ void LightStorage::update_light_buffers(RenderDataRD *p_render_data, const Paged
 						float bias_scale = light_instance->shadow_transform[j].bias_scale * light_data.soft_shadow_scale;
 						light_data.shadow_bias[j] = light->param[RS::LIGHT_PARAM_SHADOW_BIAS] / 100.0 * bias_scale;
 						light_data.shadow_normal_bias[j] = light->param[RS::LIGHT_PARAM_SHADOW_NORMAL_BIAS] * light_instance->shadow_transform[j].shadow_texel_size;
-						light_data.shadow_transmittance_bias[j] = light->param[RS::LIGHT_PARAM_TRANSMITTANCE_BIAS] * bias_scale;
+						light_data.shadow_transmittance_bias[j] = light->param[RS::LIGHT_PARAM_TRANSMITTANCE_BIAS] / 100.0 * bias_scale;
 						light_data.shadow_z_range[j] = light_instance->shadow_transform[j].farplane;
 						light_data.shadow_range_begin[j] = light_instance->shadow_transform[j].range_begin;
 						RendererRD::MaterialStorage::store_camera(shadow_mtx, light_data.shadow_matrices[j]);