rt: add very basic support for emissive textures

They only affect what's visible on screen and bounces. They don't
participate in lighting directly as light sources.

Adding them as light sources is a bit trickier (and more expensive too).
Arbitrary model with arbitrary emissive textures support would be very
difficult, especially wrt sampling strategies.

ref/vk/shaders/ray_interop.h

@@ -80,18 +80,22 @@ struct Material {
 
 	uint tex_base_color;
 
-	// TODO can be combined into a single texture
+	// TODO these three can be combined into a single texture
 	uint tex_roughness;
 	uint tex_metalness;
 	uint tex_normalmap;
 
+	uint tex_emissive;
+
 	// TODO:
-	// uint tex_emissive;
 	// uint tex_detail;
 
 	float roughness;
 	float metalness;
 	float normal_scale;
+	float emissive_scale;
+
+	PAD(2)
 };
 
 struct ModelMetadata {

ref/vk/shaders/ray_primary_hit.glsl

@@ -62,7 +62,12 @@ void primaryRayHit(rayQueryEXT rq, inout RayPayloadPrimary payload) {
 	//payload.emissive.rgb = kusok.emissive * SRGBtoLINEAR(payload.base_color_a.rgb);
 	//payload.emissive.rgb = clamp((kusok.emissive * (1.0/3.0) / 20), 0, 1.0) * SRGBtoLINEAR(payload.base_color_a.rgb);
 	//payload.emissive.rgb = (sqrt(sqrt(kusok.emissive)) * (1.0/3.0)) * SRGBtoLINEAR(payload.base_color_a.rgb);
-	payload.emissive.rgb = (sqrt(kusok.emissive) / 8) * SRGBtoLINEAR(payload.base_color_a.rgb);
+	if (material.tex_emissive == 0) {
+		payload.emissive.rgb = (sqrt(kusok.emissive) / 8) * SRGBtoLINEAR(payload.base_color_a.rgb);
+	} else {
+		const vec3 emissive = sampleTexture(material.tex_emissive, geom.uv, geom.uv_lods).rgb;
+		payload.emissive.rgb = kusok.material.emissive_scale * emissive;
+	}
 #else
 	// Fake texture color
 	if (any(greaterThan(kusok.emissive, vec3(0.))))

ref/vk/vk_materials.c

@@ -13,10 +13,12 @@ static xvk_material_t k_default_material = {
 		.tex_metalness = 0,
 		.tex_roughness = 0,
 		.tex_normalmap = 0,
+		.tex_emissive = 0,
 
 		.metalness = 0.f,
 		.roughness = 1.f,
 		.normal_scale = 1.f,
+		.emissive_scale = 1.f,
 		.base_color = { 1.f, 1.f, 1.f, 1.f },
 
 		.set = false,
@@ -153,6 +155,8 @@ static void loadMaterialsFromFile( const char *filename, int depth ) {
 				tex_id_dest = &current_material.tex_metalness;
 			} else if (Q_stricmp(key, "roughness_map") == 0) {
 				tex_id_dest = &current_material.tex_roughness;
+			} else if (Q_stricmp(key, "emissive_map") == 0) {
+				tex_id_dest = &current_material.tex_emissive;
 			} else if (Q_stricmp(key, "roughness") == 0) {
 				sscanf(value, "%f", &current_material.roughness);
 			} else if (Q_stricmp(key, "metalness") == 0) {
@@ -160,6 +164,8 @@ static void loadMaterialsFromFile( const char *filename, int depth ) {
 				metalness_set = true;
 			} else if (Q_stricmp(key, "normal_scale") == 0) {
 				sscanf(value, "%f", &current_material.normal_scale);
+			} else if (Q_stricmp(key, "emissive") == 0) {
+				sscanf(value, "%f", &current_material.emissive_scale);
 			} else if (Q_stricmp(key, "base_color") == 0) {
 				sscanf(value, "%f %f %f %f", &current_material.base_color[0], &current_material.base_color[1], &current_material.base_color[2], &current_material.base_color[3]);
 			} else {

ref/vk/vk_materials.h

@@ -7,11 +7,13 @@ typedef struct {
 	int tex_roughness;
 	int tex_metalness;
 	int tex_normalmap;
+	int tex_emissive;
 
 	vec4_t base_color;
 	float roughness;
 	float metalness;
 	float normal_scale;
+	float emissive_scale;
 
 	qboolean set;
 } xvk_material_t;

ref/vk/vk_ray_model.c

@@ -172,10 +172,12 @@ static void applyMaterialToKusok(vk_kusok_data_t* kusok, const vk_render_geometr
 		.tex_roughness = mat->tex_roughness,
 		.tex_metalness = mat->tex_metalness,
 		.tex_normalmap = mat->tex_normalmap,
+		.tex_emissive = mat->tex_emissive,
 
 		.roughness = mat->roughness,
 		.metalness = mat->metalness,
 		.normal_scale = mat->normal_scale,
+		.emissive_scale = mat->emissive_scale,
 	};
 
 	const qboolean HACK_chrome = geom->material == kXVkMaterialChrome;