rt: add alpha-quality alpha blending

Do translucency in bounce stage. It's not great, but lets us see thing through.

Also fix reading OOB uninitialized memory for color/alpha.

ref_vk/shaders/bounce.comp

@@ -12,7 +12,8 @@ layout(set=0, binding=1) uniform accelerationStructureEXT tlas;
 #define RAY_LIGHT_DIRECT_INPUTS(X) \
 	X(10, position_t, rgba32f) \
 	X(11, normals_gs, rgba16f) \
-	X(12, material_rmxx, rgba8)
+	X(12, material_rmxx, rgba8) \
+	X(13, base_color_a, rgba8)
 #define X(index, name, format) layout(set=0,binding=index,format) uniform readonly image2D name;
 RAY_LIGHT_DIRECT_INPUTS(X)
 #undef X
@@ -92,9 +93,10 @@ void computeBounce(ivec2 pix, vec3 direction, out vec3 diffuse, out vec3 specula
 	specular = vec3(0.);
 
 	const vec4 material_data = imageLoad(material_rmxx, pix);
+	const vec4 base_a = imageLoad(base_color_a, pix);
 
 	MaterialProperties material;
-	material.baseColor = vec3(1.);
+	material.baseColor = vec3(1.f);
 	material.emissive = vec3(0.f);
 	material.metalness = material_data.g;
 	material.roughness = material_data.r;
@@ -103,14 +105,20 @@ void computeBounce(ivec2 pix, vec3 direction, out vec3 diffuse, out vec3 specula
 	readNormals(pix, geometry_normal, shading_normal);
 
 	const float ray_normal_fudge = .01;
-	const vec3 pos = imageLoad(position_t, pix).xyz + geometry_normal * ray_normal_fudge;
 	vec3 throughput = vec3(1.);
 
 	// 1. Make a "random" material-based ray for diffuse lighting
 	vec3 bounce_direction = vec3(0.);
-	vec3 brdf_weight = vec3(0.);
 	int brdf_type = DIFFUSE_TYPE;
 
+	const float alpha = (base_a.a);
+	if (1. > alpha && rand01() > alpha) {
+		brdf_type = SPECULAR_TYPE;
+		// TODO: when not sampling randomly: throughput *= (1. - base_a.a);
+		bounce_direction = normalize(refract(direction, geometry_normal, .95));
+		geometry_normal = -geometry_normal;
+		//throughput /= base_a.rgb;
+	} else {
 		if (material.metalness == 1.0f && material.roughness == 0.0f) {
 			// Fast path for mirrors
 			brdf_type = SPECULAR_TYPE;
@@ -122,12 +130,15 @@ void computeBounce(ivec2 pix, vec3 direction, out vec3 diffuse, out vec3 specula
 				throughput /= brdf_probability;
 			}
 		}
+
 		const vec2 u = vec2(rand01(), rand01());
+		vec3 brdf_weight = vec3(0.);
 		if (!evalIndirectCombinedBRDF(u, shading_normal, geometry_normal, -direction, material, brdf_type, bounce_direction, brdf_weight))
 			return;
+		throughput *= brdf_weight;
+	}
 
 	const float throughput_threshold = 1e-3;
-	throughput *= brdf_weight;
 	if (dot(throughput, throughput) < throughput_threshold)
 		return;
 
@@ -136,6 +147,7 @@ void computeBounce(ivec2 pix, vec3 direction, out vec3 diffuse, out vec3 specula
 	RayPayloadPrimary payload;
 	payload.base_color_a = vec4(0.);
 	payload.emissive = vec4(0.);
+	const vec3 pos = imageLoad(position_t, pix).xyz + geometry_normal * ray_normal_fudge;
 	if (!getHit(pos, bounce_direction, payload))
 		return;
 

ref_vk/shaders/ray_primary.comp

@@ -54,7 +54,7 @@ void main() {
 		//| gl_RayFlagsSkipClosestHitShaderEXT
 		;
 	float L = 10000.; // TODO Why 10k?
-	rayQueryInitializeEXT(rq, tlas, flags, GEOMETRY_BIT_OPAQUE | GEOMETRY_BIT_ALPHA_TEST, origin, 0., direction, L);
+	rayQueryInitializeEXT(rq, tlas, flags, GEOMETRY_BIT_OPAQUE | GEOMETRY_BIT_ALPHA_TEST | GEOMETRY_BIT_REFRACTIVE, origin, 0., direction, L);
 	while (rayQueryProceedEXT(rq)) {
 		if (0 != (rayQueryGetRayFlagsEXT(rq) & gl_RayFlagsOpaqueEXT))
 			continue;

ref_vk/vk_ray_model.c

@@ -153,7 +153,7 @@ void XVK_RayModel_Validate( void ) {
 	}
 }
 
-static void applyMaterialToKusok(vk_kusok_data_t* kusok, const vk_render_geometry_t *geom, const vec3_t color, qboolean HACK_reflective) {
+static void applyMaterialToKusok(vk_kusok_data_t* kusok, const vk_render_geometry_t *geom, const vec4_t color, qboolean HACK_reflective) {
 	const xvk_material_t *const mat = XVK_GetMaterialForTextureIndex( geom->texture );
 	ASSERT(mat);
 
@@ -299,7 +299,7 @@ vk_ray_model_t* VK_RayModelCreate( vk_ray_model_init_t args ) {
 			kusochki[i].tex_base_color &= (~KUSOK_MATERIAL_FLAG_SKYBOX);
 		}
 
-		const vec3_t color = {1, 1, 1};
+		const vec4_t color = {1, 1, 1, 1};
 		applyMaterialToKusok(kusochki + i, mg, color, false);
 		Matrix4x4_LoadIdentity(kusochki[i].prev_transform);
 	}