Invert spotlight angle attenuation

Inverted the spotlight angle attenuation so a higher value results in
a dimmer light, this makes it more consistent with the distance
attenuation.

Also changed the way spotlighs are computed in SDFGI
and GIPorbes and GPU lightmapper, now it matches the falloff used in the scene rendering
code.

5 files changed, 41 insertions, 34 deletions

diff --git a/servers/rendering/renderer_rd/renderer_scene_render_rd.cpp b/servers/rendering/renderer_rd/renderer_scene_render_rd.cpp
index 14bcfc85c8..09d2c032a8 100644
--- a/servers/rendering/renderer_rd/renderer_scene_render_rd.cpp
+++ b/servers/rendering/renderer_rd/renderer_scene_render_rd.cpp
@@ -1611,8 +1611,8 @@ void RendererSceneRenderRD::_pre_process_gi(RID p_render_buffers, const Transfor
 				lights[idx].has_shadow = storage->light_has_shadow(li->light);
 				lights[idx].attenuation = storage->light_get_param(li->light, RS::LIGHT_PARAM_ATTENUATION);
 				lights[idx].radius = storage->light_get_param(li->light, RS::LIGHT_PARAM_RANGE);
-				lights[idx].spot_angle = Math::deg2rad(storage->light_get_param(li->light, RS::LIGHT_PARAM_SPOT_ANGLE));
-				lights[idx].spot_attenuation = storage->light_get_param(li->light, RS::LIGHT_PARAM_SPOT_ATTENUATION);
+				lights[idx].cos_spot_angle = Math::cos(Math::deg2rad(storage->light_get_param(li->light, RS::LIGHT_PARAM_SPOT_ANGLE)));
+				lights[idx].inv_spot_attenuation = 1.0f / storage->light_get_param(li->light, RS::LIGHT_PARAM_SPOT_ATTENUATION);
 
 				idx++;
 			}
@@ -4539,8 +4539,8 @@ void RendererSceneRenderRD::gi_probe_update(RID p_probe, bool p_update_light_ins
 				l.color[1] = color.g;
 				l.color[2] = color.b;
 
-				l.spot_angle_radians = Math::deg2rad(storage->light_get_param(light, RS::LIGHT_PARAM_SPOT_ANGLE));
-				l.spot_attenuation = storage->light_get_param(light, RS::LIGHT_PARAM_SPOT_ATTENUATION);
+				l.cos_spot_angle = Math::cos(Math::deg2rad(storage->light_get_param(light, RS::LIGHT_PARAM_SPOT_ANGLE)));
+				l.inv_spot_attenuation = 1.0f / storage->light_get_param(light, RS::LIGHT_PARAM_SPOT_ATTENUATION);
 
 				Transform xform = light_instance_get_base_transform(light_instance);
 
@@ -6491,9 +6491,9 @@ void RendererSceneRenderRD::_setup_lights(const PagedArray<RID> &p_lights, const
 
 		light_data.size = size;
 
-		light_data.cone_attenuation = storage->light_get_param(base, RS::LIGHT_PARAM_SPOT_ATTENUATION);
+		light_data.inv_spot_attenuation = 1.0f / storage->light_get_param(base, RS::LIGHT_PARAM_SPOT_ATTENUATION);
 		float spot_angle = storage->light_get_param(base, RS::LIGHT_PARAM_SPOT_ANGLE);
-		light_data.cone_angle = Math::cos(Math::deg2rad(spot_angle));
+		light_data.cos_spot_angle = Math::cos(Math::deg2rad(spot_angle));
 
 		light_data.mask = storage->light_get_cull_mask(base);
 
@@ -8094,8 +8094,8 @@ void RendererSceneRenderRD::_render_sdfgi_static_lights(RID p_render_buffers, ui
 				lights[idx].has_shadow = storage->light_has_shadow(li->light);
 				lights[idx].attenuation = storage->light_get_param(li->light, RS::LIGHT_PARAM_ATTENUATION);
 				lights[idx].radius = storage->light_get_param(li->light, RS::LIGHT_PARAM_RANGE);
-				lights[idx].spot_angle = Math::deg2rad(storage->light_get_param(li->light, RS::LIGHT_PARAM_SPOT_ANGLE));
-				lights[idx].spot_attenuation = storage->light_get_param(li->light, RS::LIGHT_PARAM_SPOT_ATTENUATION);
+				lights[idx].cos_spot_angle = Math::cos(Math::deg2rad(storage->light_get_param(li->light, RS::LIGHT_PARAM_SPOT_ANGLE)));
+				lights[idx].inv_spot_attenuation = 1.0f / storage->light_get_param(li->light, RS::LIGHT_PARAM_SPOT_ATTENUATION);
 
 				idx++;
 			}
diff --git a/servers/rendering/renderer_rd/renderer_scene_render_rd.h b/servers/rendering/renderer_rd/renderer_scene_render_rd.h
index 8b4f41b6f7..cdcdb73132 100644
--- a/servers/rendering/renderer_rd/renderer_scene_render_rd.h
+++ b/servers/rendering/renderer_rd/renderer_scene_render_rd.h
@@ -406,10 +406,10 @@ private:
 		float attenuation;
 
 		float color[3];
-		float spot_angle_radians;
+		float cos_spot_angle;
 
 		float position[3];
-		float spot_attenuation;
+		float inv_spot_attenuation;
 
 		float direction[3];
 		uint32_t has_shadow;
@@ -1146,8 +1146,8 @@ private:
 			float attenuation;
 
 			uint32_t type;
-			float spot_angle;
-			float spot_attenuation;
+			float cos_spot_angle;
+			float inv_spot_attenuation;
 			float radius;
 
 			float shadow_color[4];
@@ -1362,8 +1362,8 @@ private:
 			float color[3];
 			float attenuation;
 
-			float cone_attenuation;
-			float cone_angle;
+			float inv_spot_attenuation;
+			float cos_spot_angle;
 			float specular_amount;
 			uint32_t shadow_enabled;
 
diff --git a/servers/rendering/renderer_rd/shaders/giprobe.glsl b/servers/rendering/renderer_rd/shaders/giprobe.glsl
index 4f4753d147..b931461b31 100644
--- a/servers/rendering/renderer_rd/shaders/giprobe.glsl
+++ b/servers/rendering/renderer_rd/shaders/giprobe.glsl
@@ -51,10 +51,10 @@ struct Light {
 	float attenuation;
 
 	vec3 color;
-	float spot_angle_radians;
+	float cos_spot_angle;
 
 	vec3 position;
-	float spot_attenuation;
+	float inv_spot_attenuation;
 
 	vec3 direction;
 	bool has_shadow;
@@ -233,13 +233,15 @@ bool compute_light_vector(uint light, vec3 pos, out float attenuation, out vec3
 
 		if (lights.data[light].type == LIGHT_TYPE_SPOT) {
 			vec3 rel = normalize(pos - light_pos);
-			float angle = acos(dot(rel, lights.data[light].direction));
-			if (angle > lights.data[light].spot_angle_radians) {
+			float cos_spot_angle = lights.data[light].cos_spot_angle;
+			float cos_angle = dot(rel, lights.data[light].direction);
+			if (cos_angle < cos_spot_angle) {
 				return false;
 			}
 
-			float d = clamp(angle / lights.data[light].spot_angle_radians, 0, 1);
-			attenuation *= pow(1.0 - d, lights.data[light].spot_attenuation);
+			float scos = max(cos_angle, cos_spot_angle);
+			float spot_rim = max(0.0001, (1.0 - scos) / (1.0 - cos_spot_angle));
+			attenuation *= 1.0 - pow(spot_rim, lights.data[light].inv_spot_attenuation);
 		}
 	}
 
diff --git a/servers/rendering/renderer_rd/shaders/giprobe_write.glsl b/servers/rendering/renderer_rd/shaders/giprobe_write.glsl
index 9c794f1bcc..56b3b7ccb4 100644
--- a/servers/rendering/renderer_rd/shaders/giprobe_write.glsl
+++ b/servers/rendering/renderer_rd/shaders/giprobe_write.glsl
@@ -43,10 +43,10 @@ struct Light {
 	float attenuation;
 
 	vec3 color;
-	float spot_angle_radians;
+	float cos_spot_angle;
 
 	vec3 position;
-	float spot_attenuation;
+	float inv_spot_attenuation;
 
 	vec3 direction;
 	bool has_shadow;
@@ -146,13 +146,15 @@ bool compute_light_vector(uint light, uint cell, vec3 pos, out float attenuation
 
 		if (lights.data[light].type == LIGHT_TYPE_SPOT) {
 			vec3 rel = normalize(pos - light_pos);
-			float angle = acos(dot(rel, lights.data[light].direction));
-			if (angle > lights.data[light].spot_angle_radians) {
+			float cos_spot_angle = lights.data[light].cos_spot_angle;
+			float cos_angle = dot(rel, lights.data[light].direction);
+			if (cos_angle < cos_spot_angle) {
 				return false;
 			}
 
-			float d = clamp(angle / lights.data[light].spot_angle_radians, 0, 1);
-			attenuation *= pow(1.0 - d, lights.data[light].spot_attenuation);
+			float scos = max(cos_angle, cos_spot_angle);
+			float spot_rim = max(0.0001, (1.0 - scos) / (1.0 - cos_spot_angle));
+			attenuation *= 1.0 - pow(spot_rim, lights.data[light].inv_spot_attenuation);
 		}
 	}
 
diff --git a/servers/rendering/renderer_rd/shaders/sdfgi_direct_light.glsl b/servers/rendering/renderer_rd/shaders/sdfgi_direct_light.glsl
index bcdfe8cc85..5e8934adb4 100644
--- a/servers/rendering/renderer_rd/shaders/sdfgi_direct_light.glsl
+++ b/servers/rendering/renderer_rd/shaders/sdfgi_direct_light.glsl
@@ -67,8 +67,8 @@ struct Light {
 	float attenuation;
 
 	uint type;
-	float spot_angle;
-	float spot_attenuation;
+	float cos_spot_angle;
+	float inv_spot_attenuation;
 	float radius;
 
 	vec4 shadow_color;
@@ -266,13 +266,16 @@ void main() {
 				rel_vec.y /= params.y_mult;
 				attenuation = get_omni_attenuation(light_distance, 1.0 / lights.data[i].radius, lights.data[i].attenuation);
 
-				float angle = acos(dot(normalize(rel_vec), -lights.data[i].direction));
-				if (angle > lights.data[i].spot_angle) {
-					attenuation = 0.0;
-				} else {
-					float d = clamp(angle / lights.data[i].spot_angle, 0, 1);
-					attenuation *= pow(1.0 - d, lights.data[i].spot_attenuation);
+				float cos_spot_angle = lights.data[i].cos_spot_angle;
+				float cos_angle = dot(-direction, lights.data[i].direction);
+
+				if (cos_angle < cos_spot_angle) {
+					continue;
 				}
+
+				float scos = max(cos_angle, cos_spot_angle);
+				float spot_rim = max(0.0001, (1.0 - scos) / (1.0 - cos_spot_angle));
+				attenuation *= 1.0 - pow(spot_rim, lights.data[i].inv_spot_attenuation);
 			} break;
 		}