vk: rt: fixup environment attenuation

Now environment emissive strength also depends on cos_theta (derived
from sun solid angle).

ref/vk/TODO.md

@@ -1,19 +1,19 @@
 # 2024-01-16 E364
 - [x] P NaNs
 	- [x] need to remove degenerate triangles
-- [ ] add direct_{diff,spec} to rendertests
-	- [ ] and rerun tests for vulkan to get new gold images
-- [ ] light_environment is too dark
+- [x] light_environment is too dark
+- [ ] add direct_{diff,spec} to rendertests → only can do for this handmade-brdfs branch
+	- [ ] :x: and rerun tests for vulkan to get new gold images → imuposshiburu, see above
 - [ ] patchable sun angle
 
 # 2024-01-15 E363
 - [x] filter out invalid (r=0, etc) lights in native
-	- [-] already do; it seems that clusters are not getting updates → see #730
+	- [-] :o: already do; it seems that clusters are not getting updates → see #730
 - [x] pass point lights r² directly?
 - [x] move empirical scaling to native code
 - [x] modify point light radius in entity patches → already done
 	- [x] adjust brightness based on radius? → already done
-- [ ] ~~common intersection-local-normal-oriented basis~~ → point light construct light-oriented frames, not reusable
+- [ ] :x: ~~common intersection-local-normal-oriented basis~~ → point light construct light-oriented frames, not reusable
 
 # 2024-01-12 E362
 - [ ] point→spherical light sampling
@@ -27,7 +27,7 @@
 	- [ ] need proper sampling asap, as different instabilities approaches are visually different, and it's impossible to reason which one is preferable
 - [x] add material debug display mode
 - [ ] vulkan validation layers crashes on too many `debugPrintfEXT` messages
-- [ ] diffuse is stil way darker than before
+- [ ] diffuse is still way darker than before
 
 # 2024-01-09 E360
 - [x] validate all intermediate and final outputs against invalid values, complain into log

ref/vk/shaders/light.glsl

@@ -43,13 +43,10 @@ void computePointLights(vec3 P, vec3 N, uint cluster_index, vec3 view_dir, Mater
 		vec3 light_dir;
 		vec3 color = lights.m.point_lights[i].color_stopdot.rgb;
 		float light_dist = 0.;
+		float one_over_pdf = 1.;
 		if (is_environment) {
 			// Environment/directional light
-			// FIXME extract, it is very different from other point/sphere/spotlights
-
-			// Empirical? TODO WHY?
-			// TODO move to native code
-			color *= 2.;
+			// FIXME extract, it is rather different from other point/sphere/spotlights
 
 			// TODO parametrize externally, via entity patches, etc
 			const float sun_solid_angle = 6.794e-5; // Wikipedia
@@ -62,7 +59,9 @@ void computePointLights(vec3 P, vec3 N, uint cluster_index, vec3 view_dir, Mater
 			const float light_dot = dot(light_dir, N);
 			if (light_dot < 1e-5)
 				continue;
-		} else {
+
+			one_over_pdf = 2. * kPi * max(0., 1. - cos_theta_max);
+		} /* is_environment */ else {
 			// Spherical lights
 			const vec3 light_pos = lights.m.point_lights[i].origin_r2.xyz;
 			const float light_r2 = lights.m.point_lights[i].origin_r2.w;
@@ -154,17 +153,17 @@ void computePointLights(vec3 P, vec3 N, uint cluster_index, vec3 view_dir, Mater
 			// d2=4489108.500000 r2=1.000000 dist=2118.751465 spot_attenuation=0.092902 INVALID pdf=-316492608.000000
 			// Therefore, need to clamp denom with max
 			// TODO need better sampling right nao
-			const float one_over_pdf = 2. * kPi * max(0., 1. - cos_theta_max) * spot_attenuation;
+			one_over_pdf = 2. * kPi * max(0., 1. - cos_theta_max) * spot_attenuation;
 #ifdef DEBUG_VALIDATE_EXTRA
 			if (IS_INVALID(one_over_pdf) || one_over_pdf < 0.) {
 				debugPrintfEXT("light.glsl:%d light_dist2=%f light_r2=%f light_dist=%f spot_attenuation=%f INVALID one_over_pdf=%f",
 					__LINE__, light_dist2, light_r2, light_dist, spot_attenuation, one_over_pdf);
 			}
 #endif
-
-			color *= one_over_pdf;
 		} // Sphere/spot lights
 
+		color *= one_over_pdf;
+
 		vec3 ldiffuse, lspecular;
 		evalSplitBRDF(N, light_dir, view_dir, material, ldiffuse, lspecular);
 		ldiffuse *= color;

ref/vk/vk_light.c

@@ -893,8 +893,9 @@ static void processStaticPointLights( void ) {
 		const float radius = le->radius > 0.f ? le->radius : default_radius;
 
 		// These constants are empirical. There's no known math reason behind them
-		const float hack_attenuation = .1f / 25.f; // FIXME tune
-		const float hack_attenuation_spot = .1f / 25.f; // FIXME tune
+		const float hack_attenuation = (le->type == LightTypeEnvironment)
+			? 700.f // FIXME why?
+			: .1f / 25.f; // FIXME why?
 
 		int index;
 		switch (le->type) {
@@ -902,9 +903,9 @@ static void processStaticPointLights( void ) {
 				index = addPointLight(le->origin, le->color, radius, le->style, hack_attenuation);
 				break;
 
-			case LightTypeSpot:
 			case LightTypeEnvironment:
-				index = addSpotLight(le, radius, le->style, hack_attenuation_spot, i == g_map_entities.single_environment_index);
+			case LightTypeSpot:
+				index = addSpotLight(le, radius, le->style, hack_attenuation, i == g_map_entities.single_environment_index);
 				break;
 
 			default: