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.

4 files changed, 13 insertions, 10 deletions

diff --git a/modules/lightmapper_rd/lightmapper_rd.cpp b/modules/lightmapper_rd/lightmapper_rd.cpp
index f31eb3f066..82aaa492fc 100644
--- a/modules/lightmapper_rd/lightmapper_rd.cpp
+++ b/modules/lightmapper_rd/lightmapper_rd.cpp
@@ -93,8 +93,8 @@ void LightmapperRD::add_spot_light(bool p_static, const Vector3 &p_position, con
 	l.direction[2] = p_direction.z;
 	l.range = p_range;
 	l.attenuation = p_attenuation;
-	l.spot_angle = Math::deg2rad(p_spot_angle);
-	l.spot_attenuation = p_spot_attenuation;
+	l.cos_spot_angle = Math::cos(Math::deg2rad(p_spot_angle));
+	l.inv_spot_attenuation = 1.0f / p_spot_attenuation;
 	l.color[0] = p_color.r;
 	l.color[1] = p_color.g;
 	l.color[2] = p_color.b;
diff --git a/modules/lightmapper_rd/lightmapper_rd.h b/modules/lightmapper_rd/lightmapper_rd.h
index bb735baf6c..1c360bd0ab 100644
--- a/modules/lightmapper_rd/lightmapper_rd.h
+++ b/modules/lightmapper_rd/lightmapper_rd.h
@@ -54,8 +54,8 @@ class LightmapperRD : public Lightmapper {
 		float size;
 		float range;
 		float attenuation;
-		float spot_angle;
-		float spot_attenuation;
+		float cos_spot_angle;
+		float inv_spot_attenuation;
 		uint32_t static_bake;
 		uint32_t pad[3];
 
diff --git a/modules/lightmapper_rd/lm_common_inc.glsl b/modules/lightmapper_rd/lm_common_inc.glsl
index 0ff455936e..f8a0cd16de 100644
--- a/modules/lightmapper_rd/lm_common_inc.glsl
+++ b/modules/lightmapper_rd/lm_common_inc.glsl
@@ -56,8 +56,8 @@ struct Light {
 
 	float range;
 	float attenuation;
-	float spot_angle;
-	float spot_attenuation;
+	float cos_spot_angle;
+	float inv_spot_attenuation;
 
 	bool static_bake;
 	uint pad[3];
diff --git a/modules/lightmapper_rd/lm_compute.glsl b/modules/lightmapper_rd/lm_compute.glsl
index 8a9adbc5cc..eb9d817f99 100644
--- a/modules/lightmapper_rd/lm_compute.glsl
+++ b/modules/lightmapper_rd/lm_compute.glsl
@@ -313,13 +313,16 @@ void main() {
 
 			if (lights.data[i].type == LIGHT_TYPE_SPOT) {
 				vec3 rel = normalize(position - light_pos);
-				float angle = acos(dot(rel, lights.data[i].direction));
-				if (angle > lights.data[i].spot_angle) {
+				float cos_spot_angle = lights.data[i].cos_spot_angle;
+				float cos_angle = dot(rel, lights.data[i].direction);
+
+				if (cos_angle < cos_spot_angle) {
 					continue; //invisible, dont try
 				}
 
-				float d = clamp(angle / lights.data[i].spot_angle, 0, 1);
-				attenuation *= pow(1.0 - d, lights.data[i].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[i].inv_spot_attenuation);
 			}
 		}