vk: rt: move empirical light scaling to native code

There are lots of empirical (and less-well undrestood things) scaling
color values in native code, it makes sense to consolidate them in one
place:
- less weird math in shaders. shader should be as streamlined as
  possible
- one big block of weird math is untangleable in the future when we get
  to work on light and clusters

ref/vk/TODO.md

@@ -2,12 +2,14 @@
 - [x] filter out invalid (r=0, etc) lights in native
 	- [-] already do; it seems that clusters are not getting updates → see #730
 - [x] pass point lights r² directly?
-- [ ] move empirical scaling to native code
+- [x] move empirical scaling to native code
 - [ ] modify point light radius in entity patches
-- [ ] adjust brightness based on radius?
+	- [ ] adjust brightness based on radius?
 - [ ] P NaNs
 - [ ] patchable sun angle
 - [ ] common intersection-local-normal-oriented basis
+- [ ] add direct_{diff,spec} to rendertests
+	- [ ] and rerun tests for vulkan to get new gold images
 
 # 2024-01-12 E362
 - [ ] point→spherical light sampling

ref/vk/shaders/light.glsl

@@ -207,20 +207,11 @@ void computeLighting(vec3 P, vec3 N, vec3 view_dir, MaterialProperties material,
 
 #if LIGHT_POLYGON
 	sampleEmissiveSurfaces(P, N, view_dir, material, cluster_index, diffuse, specular);
-	// These constants are empirical. There's no known math reason behind them
-	// TODO move to native code
-	diffuse /= 25.0;
-	specular /= 25.0;
 #endif
 
 #if LIGHT_POINT
 	vec3 ldiffuse = vec3(0.), lspecular = vec3(0.);
 	computePointLights(P, N, cluster_index, view_dir, material, ldiffuse, lspecular);
-	// These constants are empirical. There's no known math reason behind them
-	// TODO move to native code
-	ldiffuse /= 25.;
-	lspecular /= 25.;
-
 	diffuse += ldiffuse;
 	specular += lspecular;
 #endif

ref/vk/vk_light.c

@@ -868,6 +868,9 @@ static qboolean addDlight( const dlight_t *dlight ) {
 
 	scaler = k_threshold / (max_comp * sphereSolidAngleFromDistDiv2Pi(k_light_radius, dlight->radius));
 
+	// These constants are empirical. There's no known math reason behind them
+	scaler /= 25.;
+
 	VectorSet(
 		color,
 		dlight->color.r * scaler,
@@ -887,11 +890,13 @@ static void processStaticPointLights( void ) {
 	for (int i = 0; i < g_map_entities.num_lights; ++i) {
 		const vk_light_entity_t *le = g_map_entities.lights + i;
 		const float default_radius = 2.f; // FIXME tune
-		const float hack_attenuation = .1f; // FIXME tune
-		const float hack_attenuation_spot = .1f; // FIXME tune
 		const float radius = le->radius > 0.f ? le->radius : default_radius;
-		int index;
 
+		// 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
+
+		int index;
 		switch (le->type) {
 			case LightTypePoint:
 				index = addPointLight(le->origin, le->color, radius, le->style, hack_attenuation);
@@ -1089,7 +1094,12 @@ int RT_LightAddPolygon(const rt_light_add_polygon_t *addpoly) {
 		poly->vertices.offset = g_lights_.num_polygon_vertices;
 		poly->vertices.count = addpoly->num_vertices;
 
-		VectorCopy(addpoly->emissive, poly->emissive);
+		{
+			// These constants are empirical. There's no known math reason behind them
+			const float hack_attenuation_poly = 1.f / 25.f;
+			VectorScale(addpoly->emissive, hack_attenuation_poly, poly->emissive);
+		}
+
 		VectorSet(poly->center, 0, 0, 0);
 		VectorSet(normal, 0, 0, 0);