Fix directional shadow bias

* Simplified code a lot, bias based on normalized cascade size.
* Lets scale cascades, max distance, etc. without creating acne.
* Fixed normal biasing in directional shadows.

I removed normal biasing in both omni and spot shadows, since the technique can't be easily implemented there.
Will need to be replaced by something else.

2 files changed, 8 insertions, 27 deletions

diff --git a/servers/rendering/renderer_rd/renderer_scene_render_rd.cpp b/servers/rendering/renderer_rd/renderer_scene_render_rd.cpp
index 2e0e7c3c43..27d675042f 100644
--- a/servers/rendering/renderer_rd/renderer_scene_render_rd.cpp
+++ b/servers/rendering/renderer_rd/renderer_scene_render_rd.cpp
@@ -2701,7 +2701,7 @@ void RendererSceneRenderRD::_setup_lights(const PagedArray<RID> &p_lights, const
 						CameraMatrix shadow_mtx = rectm * bias * matrix * modelview;
 						light_data.shadow_split_offsets[j] = split;
 						float bias_scale = li->shadow_transform[j].bias_scale;
-						light_data.shadow_bias[j] = storage->light_get_param(base, RS::LIGHT_PARAM_SHADOW_BIAS) * bias_scale;
+						light_data.shadow_bias[j] = storage->light_get_param(base, RS::LIGHT_PARAM_SHADOW_BIAS) / 100.0 * bias_scale;
 						light_data.shadow_normal_bias[j] = storage->light_get_param(base, RS::LIGHT_PARAM_SHADOW_NORMAL_BIAS) * li->shadow_transform[j].shadow_texel_size;
 						light_data.shadow_transmittance_bias[j] = storage->light_get_transmittance_bias(base) * bias_scale;
 						light_data.shadow_z_range[j] = li->shadow_transform[j].farplane;
@@ -2872,14 +2872,10 @@ void RendererSceneRenderRD::_setup_lights(const PagedArray<RID> &p_lights, const
 			light_data.shadow_enabled = true;
 
 			if (type == RS::LIGHT_SPOT) {
-				light_data.shadow_bias = (storage->light_get_param(base, RS::LIGHT_PARAM_SHADOW_BIAS) * radius / 10.0);
-				float shadow_texel_size = Math::tan(Math::deg2rad(spot_angle)) * radius * 2.0;
-				shadow_texel_size *= light_instance_get_shadow_texel_size(li->self, p_shadow_atlas);
-
-				light_data.shadow_normal_bias = storage->light_get_param(base, RS::LIGHT_PARAM_SHADOW_NORMAL_BIAS) * shadow_texel_size;
+				light_data.shadow_bias = (storage->light_get_param(base, RS::LIGHT_PARAM_SHADOW_BIAS) / 100.0);
 
 			} else { //omni
-				light_data.shadow_bias = storage->light_get_param(base, RS::LIGHT_PARAM_SHADOW_BIAS) * radius / 10.0;
+				light_data.shadow_bias = storage->light_get_param(base, RS::LIGHT_PARAM_SHADOW_BIAS) / 100.0;
 				float shadow_texel_size = light_instance_get_shadow_texel_size(li->self, p_shadow_atlas);
 				light_data.shadow_normal_bias = storage->light_get_param(base, RS::LIGHT_PARAM_SHADOW_NORMAL_BIAS) * shadow_texel_size * 2.0; // applied in -1 .. 1 space
 			}
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 7039ea2942..803a416303 100644
--- a/servers/rendering/renderer_rd/shaders/scene_forward_lights_inc.glsl
+++ b/servers/rendering/renderer_rd/shaders/scene_forward_lights_inc.glsl
@@ -412,14 +412,8 @@ float light_process_omni_shadow(uint idx, vec3 vertex, vec3 normal) {
 		vec4 v = vec4(vertex, 1.0);
 
 		vec4 splane = (omni_lights.data[idx].shadow_matrix * v);
-		float shadow_len = length(splane.xyz); //need to remember shadow len from here
 
-		{
-			vec3 nofs = normal_interp * omni_lights.data[idx].shadow_normal_bias / omni_lights.data[idx].inv_radius;
-			nofs *= (1.0 - max(0.0, dot(normalize(light_rel_vec), normalize(normal_interp))));
-			v.xyz += nofs;
-			splane = (omni_lights.data[idx].shadow_matrix * v);
-		}
+		float shadow_len = length(splane.xyz); //need to remember shadow len from here
 
 		float shadow;
 
@@ -528,7 +522,8 @@ float light_process_omni_shadow(uint idx, vec3 vertex, vec3 normal) {
 			splane.xy /= splane.z;
 
 			splane.xy = splane.xy * 0.5 + 0.5;
-			splane.z = (shadow_len - omni_lights.data[idx].shadow_bias) * omni_lights.data[idx].inv_radius;
+			splane.z = shadow_len * omni_lights.data[idx].inv_radius;
+			splane.z -= omni_lights.data[idx].shadow_bias;
 			splane.xy = clamp_rect.xy + splane.xy * clamp_rect.zw;
 			splane.w = 1.0; //needed? i think it should be 1 already
 			shadow = sample_pcf_shadow(shadow_atlas, omni_lights.data[idx].soft_shadow_scale * scene_data.shadow_atlas_pixel_size, splane);
@@ -704,27 +699,17 @@ float light_process_spot_shadow(uint idx, vec3 vertex, vec3 normal) {
 		//there is a shadowmap
 		vec4 v = vec4(vertex, 1.0);
 
-		v.xyz -= spot_dir * spot_lights.data[idx].shadow_bias;
-
-		float z_norm = dot(spot_dir, -light_rel_vec) * spot_lights.data[idx].inv_radius;
-
-		float depth_bias_scale = 1.0 / (max(0.0001, z_norm)); //the closer to the light origin, the more you have to offset to reach 1px in the map
-		vec3 normal_bias = normalize(normal_interp) * (1.0 - max(0.0, dot(spot_dir, -normalize(normal_interp)))) * spot_lights.data[idx].shadow_normal_bias * depth_bias_scale;
-		normal_bias -= spot_dir * dot(spot_dir, normal_bias); //only XY, no Z
-		v.xyz += normal_bias;
-
-		//adjust with bias
-		z_norm = dot(spot_dir, v.xyz - spot_lights.data[idx].position) * spot_lights.data[idx].inv_radius;
-
 		float shadow;
 
 		vec4 splane = (spot_lights.data[idx].shadow_matrix * v);
 		splane /= splane.w;
+		splane.z -= spot_lights.data[idx].shadow_bias;
 
 		if (sc_use_light_soft_shadows && spot_lights.data[idx].soft_shadow_size > 0.0) {
 			//soft shadow
 
 			//find blocker
+			float z_norm = dot(spot_dir, -light_rel_vec) * spot_lights.data[idx].inv_radius;
 
 			vec2 shadow_uv = splane.xy * spot_lights.data[idx].atlas_rect.zw + spot_lights.data[idx].atlas_rect.xy;