Add logging for KMS backend

Signed-off-by: Slendi <slendi@socopon.com>

src/Application.cpp

@@ -439,6 +439,14 @@ auto xr_rotate_vector(XrQuaternionf q, smath::Vec3 v) -> smath::Vec3
 	return (u * (2.0f * dot)) + (v * (s * s - u_dot)) + (cross * (2.0f * s));
 }
 
+[[maybe_unused]] auto xr_result_to_string(XrInstance instance, XrResult result)
+    -> std::string
+{
+	std::array<char, XR_MAX_RESULT_STRING_SIZE> buffer {};
+	xrResultToString(instance, result, buffer.data());
+	return std::string { buffer.data() };
+}
+
 } // namespace
 
 namespace Lunar {
@@ -452,6 +460,7 @@ struct OpenXrSwapchain {
 struct OpenXrState {
 	bool enabled { false };
 	bool session_running { false };
+	bool use_vulkan_enable2 { false };
 	XrInstance instance { XR_NULL_HANDLE };
 	XrSystemId system_id { XR_NULL_SYSTEM_ID };
 	XrSession session { XR_NULL_HANDLE };
@@ -466,13 +475,22 @@ struct OpenXrState {
 	std::vector<OpenXrSwapchain> swapchains {};
 	std::vector<std::string> instance_extensions {};
 	std::vector<std::string> device_extensions {};
-	PFN_xrGetVulkanGraphicsDevice2KHR get_graphics_device { nullptr };
+	PFN_xrGetVulkanGraphicsDevice2KHR get_graphics_device2 { nullptr };
+	PFN_xrGetVulkanGraphicsDeviceKHR get_graphics_device { nullptr };
+	PFN_xrGetVulkanGraphicsRequirements2KHR get_requirements2 { nullptr };
+	PFN_xrGetVulkanGraphicsRequirementsKHR get_requirements { nullptr };
+	bool hand_tracking_supported { false };
+	XrHandTrackerEXT left_hand_tracker { XR_NULL_HANDLE };
+	XrHandTrackerEXT right_hand_tracker { XR_NULL_HANDLE };
+	PFN_xrCreateHandTrackerEXT create_hand_tracker { nullptr };
+	PFN_xrDestroyHandTrackerEXT destroy_hand_tracker { nullptr };
+	PFN_xrLocateHandJointsEXT locate_hand_joints { nullptr };
 };
 
 Application::Application()
 {
-	auto const *display_env = getenv("DISPLAY");
-	auto const *wayland_env = getenv("WAYLAND_DISPLAY");
+	auto const *display_env { getenv("DISPLAY") };
+	auto const *wayland_env { getenv("WAYLAND_DISPLAY") };
 	bool const has_display
 	    = (display_env && *display_env) || (wayland_env && *wayland_env);
 	m_backend = has_display ? Backend::SDL : Backend::KMS;
@@ -560,7 +578,7 @@ auto Application::binary_directory() const -> std::filesystem::path
 		return std::filesystem::current_path();
 	}
 
-	auto const *base_path = SDL_GetBasePath();
+	auto const *base_path { SDL_GetBasePath() };
 	if (!base_path) {
 		return std::filesystem::current_path();
 	}
@@ -571,9 +589,9 @@ auto Application::asset_directory() -> std::filesystem::path
 {
 	std::vector<std::filesystem::path> candidates;
 
-	auto add_xdg_path = [&](std::filesystem::path const &base) {
+	auto const add_xdg_path { [&](std::filesystem::path const &base) {
 		candidates.emplace_back(base / "lunar" / "assets");
-	};
+	} };
 
 	if (auto const *xdg_data_home = getenv("XDG_DATA_HOME");
 	    xdg_data_home && *xdg_data_home) {
@@ -600,7 +618,7 @@ auto Application::asset_directory() -> std::filesystem::path
 		add_xdg_path("/usr/share");
 	}
 
-	auto base_dir { binary_directory() };
+	auto const base_dir { binary_directory() };
 	candidates.emplace_back(base_dir / "assets");
 	candidates.emplace_back(base_dir / "../assets");
 
@@ -618,9 +636,9 @@ auto Application::asset_directory() -> std::filesystem::path
 
 auto Application::init_test_meshes() -> void
 {
-	auto assets_dir { asset_directory() };
-	auto mesh_path { assets_dir / "basicmesh.glb" };
-	auto meshes { Mesh::load_gltf_meshes(*m_renderer, mesh_path) };
+	auto const assets_dir { asset_directory() };
+	auto const mesh_path { assets_dir / "basicmesh.glb" };
+	auto const meshes { Mesh::load_gltf_meshes(*m_renderer, mesh_path) };
 	if (!meshes) {
 		m_logger.err("Failed to load test mesh: {}", mesh_path.string());
 		return;
@@ -633,9 +651,9 @@ auto Application::run() -> void
 
 {
 	SDL_Event e;
-	bool const use_sdl = (m_backend == Backend::SDL);
-	bool const openxr_enabled = m_openxr != nullptr;
-	bool const use_imgui = use_sdl && !openxr_enabled;
+	bool const use_sdl { (m_backend == Backend::SDL) };
+	bool const openxr_enabled { m_openxr != nullptr };
+	bool const use_imgui { use_sdl && !openxr_enabled };
 
 	if (use_imgui) {
 		ImGuiIO &io = ImGui::GetIO();
@@ -939,31 +957,71 @@ auto Application::run() -> void
 			auto view { smath::matrix_look_at(
 				m_camera.position, m_camera.target, m_camera.up) };
 			auto const draw_extent = m_renderer->draw_extent();
-			auto const aspect = static_cast<float>(draw_extent.width)
+			auto const aspect = draw_extent.height == 0
+			    ? 1.0f
+			    : static_cast<float>(draw_extent.width)
 			        / static_cast<float>(draw_extent.height);
-			auto const proj = smath::matrix_perspective(
-			    m_camera.fovy, aspect, 0.1f, 10000.0f);
-			auto const view_projection = proj * view;
-			gl.set_transform(view_projection);
-			for (auto const &mesh : m_test_meshes) {
-				for (auto const &surface : mesh->surfaces) {
-					gl.draw_mesh(mesh->mesh_buffers, smath::Mat4::identity(),
-					    surface.count, surface.start_index);
-				}
-			}
-			m_skybox.draw(gl, *m_renderer, view_projection);
+			auto projection { smath::matrix_perspective(
+				m_camera.fovy, aspect, 0.1f, 10000.0f) };
+			projection[1][1] *= -1;
+			auto view_projection { projection * view };
+
+			auto skybox_view { view };
+			skybox_view[3][0] = 0.0f;
+			skybox_view[3][1] = 0.0f;
+			skybox_view[3][2] = 0.0f;
+			m_skybox.draw(gl, *m_renderer, projection * skybox_view);
 
 			gl.set_transform(view_projection);
-			gl.draw_sphere({ 0.0f, 0.0f, 0.0f }, 0.1f, 16, 32,
-			    smath::Vec4 { Colors::RED, 1.0f });
-			gl.draw_sphere({ 0.0f, 0.0f, 0.0f }, 0.11f, 16, 32,
-			    smath::Vec4 { Colors::DARK_RED, 1.0f });
+			gl.set_texture();
+			auto const &meshes { m_test_meshes };
+			if (meshes.size() > 2 && !meshes[2]->surfaces.empty()) {
+				auto const &surface = meshes[2]->surfaces[0];
+				gl.draw_mesh(meshes[2]->mesh_buffers,
+				    view_projection
+				        * smath::translate(smath::Vec3 { 0.0f, 0.0f, -5.0f }),
+				    surface.count, surface.start_index);
+			}
+
+			gl.push_transform();
+			gl.set_transform(view_projection
+			    * smath::translate(smath::Vec3 { 0.0f, 0.0f, 5.0f })
+			    * smath::Quaternion<float>::from_axis_angle(
+			        smath::Vec3 { 0.0f, 1.0f, 0.0f }, smath::deg(180))
+			        .as_matrix());
+
+			gl.set_texture(&m_renderer->white_texture());
+
+			gl.begin(VulkanRenderer::GL::GeometryKind::Quads);
+
+			gl.color(smath::Vec3 { 0.0f, 0.0f, 0.0f });
+			gl.uv(smath::Vec2 { 1.0f, 1.0f });
+			gl.vert(smath::Vec3 { 0.5f, -0.5f, 0.0f });
+
+			gl.color(smath::Vec3 { 0.5f, 0.5f, 0.5f });
+			gl.uv(smath::Vec2 { 1.0f, 0.0f });
+			gl.vert(smath::Vec3 { 0.5f, 0.5f, 0.0f });
+
+			gl.color(smath::Vec3 { 1.0f, 0.0f, 0.0f });
+			gl.uv(smath::Vec2 { 0.0f, 1.0f });
+			gl.vert(smath::Vec3 { -0.5f, -0.5f, 0.0f });
+
+			gl.color(smath::Vec3 { 0.0f, 1.0f, 0.0f });
+			gl.uv(smath::Vec2 { 0.0f, 0.0f });
+			gl.vert(smath::Vec3 { -0.5f, 0.5f, 0.0f });
+
+			gl.end();
+
 			gl.draw_rectangle({ -0.5f, 0.5f }, { 0.5f, 0.5f });
 			gl.draw_rectangle(
 			    { 0, 0.5f }, { 0.5f, 0.5f }, { Colors::TEAL, 1.0f });
 
 			gl.set_transform(view_projection);
 			gl.draw_sphere(m_camera.target, 0.01f);
+
+			if (m_openxr && m_openxr->hand_tracking_supported) {
+				render_hands(gl, view_projection);
+			}
 		};
 
 		if (xr_active) {
@@ -1031,6 +1089,9 @@ auto Application::shutdown_input() -> void
 
 auto Application::init_openxr() -> void
 {
+	if (auto const *no_xr = getenv("LUNAR_NO_XR"); no_xr && *no_xr) {
+		return;
+	}
 	m_openxr = std::make_unique<OpenXrState>();
 
 	XrInstanceCreateInfo create_info {};
@@ -1044,15 +1105,76 @@ auto Application::init_openxr() -> void
 	create_info.applicationInfo.engineVersion = 1;
 	create_info.applicationInfo.apiVersion = XR_CURRENT_API_VERSION;
 
-	std::array<char const *, 1> const extensions {
-		XR_KHR_VULKAN_ENABLE2_EXTENSION_NAME,
+	uint32_t extension_count = 0;
+	auto extension_count_result {
+		xrEnumerateInstanceExtensionProperties(
+		    nullptr, 0, &extension_count, nullptr),
 	};
+	if (XR_FAILED(extension_count_result) || extension_count == 0) {
+		m_logger.warn("OpenXR instance extensions unavailable: {}",
+		    xr_result_to_string(XR_NULL_HANDLE, extension_count_result));
+		m_openxr.reset();
+		return;
+	}
+
+	std::vector<XrExtensionProperties> available_extensions(extension_count);
+	for (auto &extension : available_extensions) {
+		extension = XrExtensionProperties {};
+		extension.type = XR_TYPE_EXTENSION_PROPERTIES;
+		extension.next = nullptr;
+	}
+	auto enumerate_result {
+		xrEnumerateInstanceExtensionProperties(nullptr, extension_count,
+		    &extension_count, available_extensions.data()),
+	};
+	if (XR_FAILED(enumerate_result)) {
+		m_logger.warn("Failed to enumerate OpenXR extensions: {}",
+		    xr_result_to_string(XR_NULL_HANDLE, enumerate_result));
+		m_openxr.reset();
+		return;
+	}
+
+	auto const has_extension { [&](char const *name) {
+		return std::any_of(available_extensions.begin(),
+		    available_extensions.end(), [&](auto const &extension) {
+			    return std::strcmp(extension.extensionName, name) == 0;
+		    });
+	} };
+
+	bool const has_enable2 {
+		has_extension(XR_KHR_VULKAN_ENABLE2_EXTENSION_NAME),
+	};
+	bool const has_enable1 = has_extension(XR_KHR_VULKAN_ENABLE_EXTENSION_NAME);
+	if (!has_enable2 && !has_enable1) {
+		m_logger.warn("OpenXR Vulkan extensions missing");
+		m_openxr.reset();
+		return;
+	}
+
+	std::vector<char const *> extensions {};
+	if (has_enable1) {
+		extensions.push_back(XR_KHR_VULKAN_ENABLE_EXTENSION_NAME);
+		m_openxr->use_vulkan_enable2 = false;
+	} else if (has_enable2) {
+		extensions.push_back(XR_KHR_VULKAN_ENABLE2_EXTENSION_NAME);
+		m_openxr->use_vulkan_enable2 = true;
+	}
+
+	bool const has_hand_tracking {
+		has_extension(XR_EXT_HAND_TRACKING_EXTENSION_NAME),
+	};
+	if (has_hand_tracking) {
+		extensions.push_back(XR_EXT_HAND_TRACKING_EXTENSION_NAME);
+		m_openxr->hand_tracking_supported = true;
+	}
+
 	create_info.enabledExtensionCount
 	    = static_cast<uint32_t>(extensions.size());
 	create_info.enabledExtensionNames = extensions.data();
 
-	auto const instance_result
-	    = xrCreateInstance(&create_info, &m_openxr->instance);
+	auto const instance_result {
+		xrCreateInstance(&create_info, &m_openxr->instance),
+	};
 	if (XR_FAILED(instance_result)) {
 		m_logger.info("OpenXR not available (no instance)");
 		m_openxr.reset();
@@ -1063,8 +1185,9 @@ auto Application::init_openxr() -> void
 	system_info.type = XR_TYPE_SYSTEM_GET_INFO;
 	system_info.next = nullptr;
 	system_info.formFactor = XR_FORM_FACTOR_HEAD_MOUNTED_DISPLAY;
-	auto const system_result
-	    = xrGetSystem(m_openxr->instance, &system_info, &m_openxr->system_id);
+	auto const system_result {
+		xrGetSystem(m_openxr->instance, &system_info, &m_openxr->system_id),
+	};
 	if (XR_FAILED(system_result)) {
 		m_logger.info("OpenXR system not detected");
 		xrDestroyInstance(m_openxr->instance);
@@ -1073,20 +1196,24 @@ auto Application::init_openxr() -> void
 	}
 
 	PFN_xrGetVulkanInstanceExtensionsKHR get_instance_exts {};
-	auto instance_ext_result = xrGetInstanceProcAddr(m_openxr->instance,
+	auto instance_ext_result {
+		xrGetInstanceProcAddr(m_openxr->instance,
 		    "xrGetVulkanInstanceExtensionsKHR",
-	    reinterpret_cast<PFN_xrVoidFunction *>(&get_instance_exts));
+		    reinterpret_cast<PFN_xrVoidFunction *>(&get_instance_exts)),
+	};
 	if (XR_FAILED(instance_ext_result) || !get_instance_exts) {
-		m_logger.warn("OpenXR missing Vulkan instance extensions");
+		m_logger.warn("OpenXR missing Vulkan instance extensions (proc)");
 		xrDestroyInstance(m_openxr->instance);
 		m_openxr.reset();
 		return;
 	}
 
 	PFN_xrGetVulkanDeviceExtensionsKHR get_device_exts {};
-	auto device_ext_result = xrGetInstanceProcAddr(m_openxr->instance,
+	auto device_ext_result {
+		xrGetInstanceProcAddr(m_openxr->instance,
 		    "xrGetVulkanDeviceExtensionsKHR",
-	    reinterpret_cast<PFN_xrVoidFunction *>(&get_device_exts));
+		    reinterpret_cast<PFN_xrVoidFunction *>(&get_device_exts)),
+	};
 	if (XR_FAILED(device_ext_result) || !get_device_exts) {
 		m_logger.warn("OpenXR missing Vulkan device extensions");
 		xrDestroyInstance(m_openxr->instance);
@@ -1116,7 +1243,7 @@ auto Application::init_openxr() -> void
 	m_openxr->instance_extensions = split_extension_list(
 	    std::string_view { instance_ext_string.c_str() });
 
-	uint32_t device_ext_size = 0;
+	uint32_t device_ext_size { 0 };
 	device_ext_result = get_device_exts(
 	    m_openxr->instance, m_openxr->system_id, 0, &device_ext_size, nullptr);
 	if (XR_FAILED(device_ext_result) || device_ext_size == 0) {
@@ -1138,14 +1265,86 @@ auto Application::init_openxr() -> void
 	    = split_extension_list(std::string_view { device_ext_string.c_str() });
 	m_openxr->enabled = true;
 
-	auto graphics_device_result = xrGetInstanceProcAddr(m_openxr->instance,
+	if (m_openxr->use_vulkan_enable2) {
+		auto const graphics_device_result {
+			xrGetInstanceProcAddr(m_openxr->instance,
 			    "xrGetVulkanGraphicsDevice2KHR",
-	    reinterpret_cast<PFN_xrVoidFunction *>(&m_openxr->get_graphics_device));
-	if (XR_FAILED(graphics_device_result) || !m_openxr->get_graphics_device) {
+			    reinterpret_cast<PFN_xrVoidFunction *>(
+			        &m_openxr->get_graphics_device2)),
+		};
+		if (XR_FAILED(graphics_device_result)
+		    || !m_openxr->get_graphics_device2) {
+			m_logger.warn("OpenXR missing Vulkan graphics device hook");
+			m_openxr->get_graphics_device2 = nullptr;
+		}
+
+		auto const requirements_result {
+			xrGetInstanceProcAddr(m_openxr->instance,
+			    "xrGetVulkanGraphicsRequirements2KHR",
+			    reinterpret_cast<PFN_xrVoidFunction *>(
+			        &m_openxr->get_requirements2)),
+		};
+		if (XR_FAILED(requirements_result) || !m_openxr->get_requirements2) {
+			m_logger.warn("OpenXR missing Vulkan requirements hook");
+			m_openxr->get_requirements2 = nullptr;
+		}
+	} else {
+		auto const graphics_device_result {
+			xrGetInstanceProcAddr(m_openxr->instance,
+			    "xrGetVulkanGraphicsDeviceKHR",
+			    reinterpret_cast<PFN_xrVoidFunction *>(
+			        &m_openxr->get_graphics_device)),
+		};
+		if (XR_FAILED(graphics_device_result)
+		    || !m_openxr->get_graphics_device) {
 			m_logger.warn("OpenXR missing Vulkan graphics device hook");
 			m_openxr->get_graphics_device = nullptr;
 		}
 
+		auto const requirements_result {
+			xrGetInstanceProcAddr(m_openxr->instance,
+			    "xrGetVulkanGraphicsRequirementsKHR",
+			    reinterpret_cast<PFN_xrVoidFunction *>(
+			        &m_openxr->get_requirements)),
+		};
+		if (XR_FAILED(requirements_result) || !m_openxr->get_requirements) {
+			m_logger.warn("OpenXR missing Vulkan requirements hook");
+			m_openxr->get_requirements = nullptr;
+		}
+	}
+
+	if (m_openxr->hand_tracking_supported) {
+		auto const create_result {
+			xrGetInstanceProcAddr(m_openxr->instance, "xrCreateHandTrackerEXT",
+			    reinterpret_cast<PFN_xrVoidFunction *>(
+			        &m_openxr->create_hand_tracker)),
+		};
+		if (XR_FAILED(create_result) || !m_openxr->create_hand_tracker) {
+			m_logger.warn("OpenXR hand tracking create function unavailable");
+			m_openxr->hand_tracking_supported = false;
+		}
+
+		auto const destroy_result {
+			xrGetInstanceProcAddr(m_openxr->instance, "xrDestroyHandTrackerEXT",
+			    reinterpret_cast<PFN_xrVoidFunction *>(
+			        &m_openxr->destroy_hand_tracker)),
+		};
+		if (XR_FAILED(destroy_result) || !m_openxr->destroy_hand_tracker) {
+			m_logger.warn("OpenXR hand tracking destroy function unavailable");
+			m_openxr->hand_tracking_supported = false;
+		}
+
+		auto const locate_result {
+			xrGetInstanceProcAddr(m_openxr->instance, "xrLocateHandJointsEXT",
+			    reinterpret_cast<PFN_xrVoidFunction *>(
+			        &m_openxr->locate_hand_joints)),
+		};
+		if (XR_FAILED(locate_result) || !m_openxr->locate_hand_joints) {
+			m_logger.warn("OpenXR hand tracking locate function unavailable");
+			m_openxr->hand_tracking_supported = false;
+		}
+	}
+
 	m_logger.info("OpenXR system detected");
 }
 
@@ -1154,50 +1353,118 @@ auto Application::init_openxr_session() -> void
 	if (!m_openxr || !m_renderer) {
 		return;
 	}
-	if (!m_openxr->get_graphics_device) {
+	VkPhysicalDevice xr_physical_device {};
+	XrGraphicsBindingVulkan2KHR binding2 {};
+	XrGraphicsBindingVulkanKHR binding1 {};
+	void *binding_ptr = nullptr;
+
+	if (m_openxr->use_vulkan_enable2) {
+		if (!m_openxr->get_graphics_device2 || !m_openxr->get_requirements2) {
 			m_logger.warn("OpenXR graphics device hook unavailable");
 			shutdown_openxr();
 			return;
 		}
 
+		XrGraphicsRequirementsVulkan2KHR requirements {};
+		requirements.type = XR_TYPE_GRAPHICS_REQUIREMENTS_VULKAN2_KHR;
+		requirements.next = nullptr;
+		auto const requirements_result {
+			m_openxr->get_requirements2(
+			    m_openxr->instance, m_openxr->system_id, &requirements),
+		};
+		if (XR_FAILED(requirements_result)) {
+			m_logger.warn("OpenXR Vulkan requirements failed: {}",
+			    xr_result_to_string(m_openxr->instance, requirements_result));
+			shutdown_openxr();
+			return;
+		}
+
 		XrVulkanGraphicsDeviceGetInfoKHR device_info {};
 		device_info.type = XR_TYPE_VULKAN_GRAPHICS_DEVICE_GET_INFO_KHR;
 		device_info.next = nullptr;
 		device_info.systemId = m_openxr->system_id;
 		device_info.vulkanInstance
 		    = static_cast<VkInstance>(m_renderer->instance());
-	VkPhysicalDevice xr_physical_device {};
-	auto const phys_result = m_openxr->get_graphics_device(
-	    m_openxr->instance, &device_info, &xr_physical_device);
+		auto const phys_result {
+			m_openxr->get_graphics_device2(
+			    m_openxr->instance, &device_info, &xr_physical_device),
+		};
 		if (XR_FAILED(phys_result)) {
-		m_logger.warn("Failed to fetch OpenXR Vulkan device");
+			m_logger.warn("Failed to fetch OpenXR Vulkan device: {}",
+			    xr_result_to_string(m_openxr->instance, phys_result));
 			shutdown_openxr();
 			return;
 		}
 
+		binding2.type = XR_TYPE_GRAPHICS_BINDING_VULKAN2_KHR;
+		binding2.next = nullptr;
+		binding2.instance = static_cast<VkInstance>(m_renderer->instance());
+		binding2.physicalDevice
+		    = static_cast<VkPhysicalDevice>(m_renderer->physical_device());
+		binding2.device = static_cast<VkDevice>(m_renderer->device());
+		binding2.queueFamilyIndex = m_renderer->graphics_queue_family();
+		binding2.queueIndex = 0;
+		binding_ptr = &binding2;
+	} else {
+		if (!m_openxr->get_graphics_device || !m_openxr->get_requirements) {
+			m_logger.warn("OpenXR graphics device hook unavailable");
+			shutdown_openxr();
+			return;
+		}
+
+		XrGraphicsRequirementsVulkanKHR requirements {};
+		requirements.type = XR_TYPE_GRAPHICS_REQUIREMENTS_VULKAN_KHR;
+		requirements.next = nullptr;
+		auto const requirements_result {
+			m_openxr->get_requirements(
+			    m_openxr->instance, m_openxr->system_id, &requirements),
+		};
+		if (XR_FAILED(requirements_result)) {
+			m_logger.warn("OpenXR Vulkan requirements failed: {}",
+			    xr_result_to_string(m_openxr->instance, requirements_result));
+			shutdown_openxr();
+			return;
+		}
+
+		auto const phys_result {
+			m_openxr->get_graphics_device(m_openxr->instance,
+			    m_openxr->system_id,
+			    static_cast<VkInstance>(m_renderer->instance()),
+			    &xr_physical_device),
+		};
+		if (XR_FAILED(phys_result)) {
+			m_logger.warn("Failed to fetch OpenXR Vulkan device: {}",
+			    xr_result_to_string(m_openxr->instance, phys_result));
+			shutdown_openxr();
+			return;
+		}
+
+		binding1.type = XR_TYPE_GRAPHICS_BINDING_VULKAN_KHR;
+		binding1.next = nullptr;
+		binding1.instance = static_cast<VkInstance>(m_renderer->instance());
+		binding1.physicalDevice
+		    = static_cast<VkPhysicalDevice>(m_renderer->physical_device());
+		binding1.device = static_cast<VkDevice>(m_renderer->device());
+		binding1.queueFamilyIndex = m_renderer->graphics_queue_family();
+		binding1.queueIndex = 0;
+		binding_ptr = &binding1;
+	}
+
 	if (xr_physical_device
 	    != static_cast<VkPhysicalDevice>(m_renderer->physical_device())) {
 		m_logger.warn("OpenXR device differs from selected Vulkan device");
 	}
 
-	XrGraphicsBindingVulkan2KHR binding {};
-	binding.type = XR_TYPE_GRAPHICS_BINDING_VULKAN2_KHR;
-	binding.next = nullptr;
-	binding.instance = static_cast<VkInstance>(m_renderer->instance());
-	binding.physicalDevice
-	    = static_cast<VkPhysicalDevice>(m_renderer->physical_device());
-	binding.device = static_cast<VkDevice>(m_renderer->device());
-	binding.queueFamilyIndex = m_renderer->graphics_queue_family();
-	binding.queueIndex = 0;
-
 	XrSessionCreateInfo session_info {};
 	session_info.type = XR_TYPE_SESSION_CREATE_INFO;
-	session_info.next = &binding;
+	session_info.next = binding_ptr;
 	session_info.systemId = m_openxr->system_id;
-	auto const session_result = xrCreateSession(
-	    m_openxr->instance, &session_info, &m_openxr->session);
+	auto const session_result {
+		xrCreateSession(m_openxr->instance, &session_info, &m_openxr->session),
+	};
 	if (XR_FAILED(session_result)) {
-		m_logger.warn("Failed to create OpenXR session");
+		m_logger.warn("Failed to create OpenXR session: {}",
+		    xr_result_to_string(m_openxr->instance, session_result));
 		shutdown_openxr();
 		return;
 	}
@@ -1207,20 +1474,25 @@ auto Application::init_openxr_session() -> void
 	space_info.next = nullptr;
 	space_info.referenceSpaceType = XR_REFERENCE_SPACE_TYPE_LOCAL;
 	space_info.poseInReferenceSpace.orientation.w = 1.0f;
-	auto const space_result = xrCreateReferenceSpace(
-	    m_openxr->session, &space_info, &m_openxr->app_space);
+	auto const space_result {
+		xrCreateReferenceSpace(
+		    m_openxr->session, &space_info, &m_openxr->app_space),
+	};
 	if (XR_FAILED(space_result)) {
-		m_logger.warn("Failed to create OpenXR space");
+		m_logger.warn("Failed to create OpenXR space: {}",
+		    xr_result_to_string(m_openxr->instance, space_result));
 		shutdown_openxr();
 		return;
 	}
 
 	uint32_t view_count = 0;
-	auto const view_count_result
-	    = xrEnumerateViewConfigurationViews(m_openxr->instance,
-	        m_openxr->system_id, m_openxr->view_type, 0, &view_count, nullptr);
+	auto const view_count_result {
+		xrEnumerateViewConfigurationViews(m_openxr->instance,
+		    m_openxr->system_id, m_openxr->view_type, 0, &view_count, nullptr),
+	};
 	if (XR_FAILED(view_count_result) || view_count == 0) {
-		m_logger.warn("OpenXR view configuration missing");
+		m_logger.warn("OpenXR view configuration missing: {}",
+		    xr_result_to_string(m_openxr->instance, view_count_result));
 		shutdown_openxr();
 		return;
 	}
@@ -1230,11 +1502,14 @@ auto Application::init_openxr_session() -> void
 		config.type = XR_TYPE_VIEW_CONFIGURATION_VIEW;
 		config.next = nullptr;
 	}
-	auto const view_result = xrEnumerateViewConfigurationViews(
-	    m_openxr->instance, m_openxr->system_id, m_openxr->view_type,
-	    view_count, &view_count, m_openxr->view_configs.data());
+	auto const view_result {
+		xrEnumerateViewConfigurationViews(m_openxr->instance,
+		    m_openxr->system_id, m_openxr->view_type, view_count, &view_count,
+		    m_openxr->view_configs.data()),
+	};
 	if (XR_FAILED(view_result)) {
-		m_logger.warn("Failed to enumerate OpenXR views");
+		m_logger.warn("Failed to enumerate OpenXR views: {}",
+		    xr_result_to_string(m_openxr->instance, view_result));
 		shutdown_openxr();
 		return;
 	}
@@ -1246,27 +1521,33 @@ auto Application::init_openxr_session() -> void
 	}
 
 	uint32_t format_count = 0;
-	auto const format_count_result = xrEnumerateSwapchainFormats(
-	    m_openxr->session, 0, &format_count, nullptr);
+	auto const format_count_result {
+		xrEnumerateSwapchainFormats(
+		    m_openxr->session, 0, &format_count, nullptr),
+	};
 	if (XR_FAILED(format_count_result) || format_count == 0) {
-		m_logger.warn("OpenXR swapchain formats unavailable");
+		m_logger.warn("OpenXR swapchain formats unavailable: {}",
+		    xr_result_to_string(m_openxr->instance, format_count_result));
 		shutdown_openxr();
 		return;
 	}
 	std::vector<int64_t> formats(format_count);
-	auto const format_result = xrEnumerateSwapchainFormats(
-	    m_openxr->session, format_count, &format_count, formats.data());
+	auto const format_result {
+		xrEnumerateSwapchainFormats(
+		    m_openxr->session, format_count, &format_count, formats.data()),
+	};
 	if (XR_FAILED(format_result)) {
-		m_logger.warn("Failed to enumerate OpenXR swapchain formats");
+		m_logger.warn("Failed to enumerate OpenXR swapchain formats: {}",
+		    xr_result_to_string(m_openxr->instance, format_result));
 		shutdown_openxr();
 		return;
 	}
 
 	std::array<int64_t, 4> const preferred_formats {
-		static_cast<int64_t>(VK_FORMAT_B8G8R8A8_SRGB),
 		static_cast<int64_t>(VK_FORMAT_B8G8R8A8_UNORM),
-		static_cast<int64_t>(VK_FORMAT_R8G8B8A8_SRGB),
+		static_cast<int64_t>(VK_FORMAT_B8G8R8A8_SRGB),
 		static_cast<int64_t>(VK_FORMAT_R8G8B8A8_UNORM),
+		static_cast<int64_t>(VK_FORMAT_R8G8B8A8_SRGB),
 	};
 	m_openxr->color_format = formats.front();
 	for (auto const preferred : preferred_formats) {
@@ -1280,7 +1561,7 @@ auto Application::init_openxr_session() -> void
 	m_openxr->swapchains.clear();
 	m_openxr->swapchains.resize(view_count);
 	for (uint32_t i = 0; i < view_count; ++i) {
-		auto const &view_config = m_openxr->view_configs[i];
+		auto const &view_config { m_openxr->view_configs[i] };
 		XrSwapchainCreateInfo swapchain_info {};
 		swapchain_info.type = XR_TYPE_SWAPCHAIN_CREATE_INFO;
 		swapchain_info.next = nullptr;
@@ -1295,10 +1576,13 @@ auto Application::init_openxr_session() -> void
 		swapchain_info.arraySize = 1;
 		swapchain_info.mipCount = 1;
 
-		auto const swapchain_result = xrCreateSwapchain(m_openxr->session,
-		    &swapchain_info, &m_openxr->swapchains[i].handle);
+		auto const swapchain_result {
+			xrCreateSwapchain(m_openxr->session, &swapchain_info,
+			    &m_openxr->swapchains[i].handle),
+		};
 		if (XR_FAILED(swapchain_result)) {
-			m_logger.warn("Failed to create OpenXR swapchain");
+			m_logger.warn("Failed to create OpenXR swapchain: {}",
+			    xr_result_to_string(m_openxr->instance, swapchain_result));
 			shutdown_openxr();
 			return;
 		}
@@ -1306,11 +1590,14 @@ auto Application::init_openxr_session() -> void
 		m_openxr->swapchains[i].extent
 		    = vk::Extent2D { swapchain_info.width, swapchain_info.height };
 
-		uint32_t image_count = 0;
-		auto const image_count_result = xrEnumerateSwapchainImages(
-		    m_openxr->swapchains[i].handle, 0, &image_count, nullptr);
+		uint32_t image_count { 0 };
+		auto const image_count_result {
+			xrEnumerateSwapchainImages(
+			    m_openxr->swapchains[i].handle, 0, &image_count, nullptr),
+		};
 		if (XR_FAILED(image_count_result) || image_count == 0) {
-			m_logger.warn("Failed to enumerate OpenXR swapchain images");
+			m_logger.warn("Failed to enumerate OpenXR swapchain images: {}",
+			    xr_result_to_string(m_openxr->instance, image_count_result));
 			shutdown_openxr();
 			return;
 		}
@@ -1320,12 +1607,15 @@ auto Application::init_openxr_session() -> void
 			image.type = XR_TYPE_SWAPCHAIN_IMAGE_VULKAN_KHR;
 			image.next = nullptr;
 		}
-		auto const image_result = xrEnumerateSwapchainImages(
-		    m_openxr->swapchains[i].handle, image_count, &image_count,
+		auto const image_result {
+			xrEnumerateSwapchainImages(m_openxr->swapchains[i].handle,
+			    image_count, &image_count,
 			    reinterpret_cast<XrSwapchainImageBaseHeader *>(
-		        m_openxr->swapchains[i].images.data()));
+			        m_openxr->swapchains[i].images.data())),
+		};
 		if (XR_FAILED(image_result)) {
-			m_logger.warn("Failed to read OpenXR swapchain images");
+			m_logger.warn("Failed to read OpenXR swapchain images: {}",
+			    xr_result_to_string(m_openxr->instance, image_result));
 			shutdown_openxr();
 			return;
 		}
@@ -1334,6 +1624,33 @@ auto Application::init_openxr_session() -> void
 	if (!m_openxr->swapchains.empty()) {
 		m_renderer->set_offscreen_extent(m_openxr->swapchains.front().extent);
 	}
+
+	if (m_openxr->hand_tracking_supported && m_openxr->create_hand_tracker) {
+		XrHandTrackerCreateInfoEXT left_info {};
+		left_info.type = XR_TYPE_HAND_TRACKER_CREATE_INFO_EXT;
+		left_info.next = nullptr;
+		left_info.hand = XR_HAND_LEFT_EXT;
+		left_info.handJointSet = XR_HAND_JOINT_SET_DEFAULT_EXT;
+		auto const left_result { m_openxr->create_hand_tracker(
+			m_openxr->session, &left_info, &m_openxr->left_hand_tracker) };
+		if (XR_FAILED(left_result)) {
+			m_logger.warn("Failed to create left hand tracker");
+			m_openxr->left_hand_tracker = XR_NULL_HANDLE;
+		}
+
+		XrHandTrackerCreateInfoEXT right_info {};
+		right_info.type = XR_TYPE_HAND_TRACKER_CREATE_INFO_EXT;
+		right_info.next = nullptr;
+		right_info.hand = XR_HAND_RIGHT_EXT;
+		right_info.handJointSet = XR_HAND_JOINT_SET_DEFAULT_EXT;
+		auto const right_result { m_openxr->create_hand_tracker(
+			m_openxr->session, &right_info, &m_openxr->right_hand_tracker) };
+		if (XR_FAILED(right_result)) {
+			m_logger.warn("Failed to create right hand tracker");
+			m_openxr->right_hand_tracker = XR_NULL_HANDLE;
+		}
+	}
+
 	m_logger.info("OpenXR session initialized");
 }
 
@@ -1351,6 +1668,18 @@ auto Application::shutdown_openxr() -> void
 	}
 	m_openxr->swapchains.clear();
 
+	if (m_openxr->left_hand_tracker != XR_NULL_HANDLE
+	    && m_openxr->destroy_hand_tracker) {
+		m_openxr->destroy_hand_tracker(m_openxr->left_hand_tracker);
+		m_openxr->left_hand_tracker = XR_NULL_HANDLE;
+	}
+
+	if (m_openxr->right_hand_tracker != XR_NULL_HANDLE
+	    && m_openxr->destroy_hand_tracker) {
+		m_openxr->destroy_hand_tracker(m_openxr->right_hand_tracker);
+		m_openxr->right_hand_tracker = XR_NULL_HANDLE;
+	}
+
 	if (m_openxr->app_space != XR_NULL_HANDLE) {
 		xrDestroySpace(m_openxr->app_space);
 		m_openxr->app_space = XR_NULL_HANDLE;
@@ -1381,9 +1710,10 @@ auto Application::poll_openxr_events() -> void
 	while (xrPollEvent(m_openxr->instance, &event) == XR_SUCCESS) {
 		switch (event.type) {
 		case XR_TYPE_EVENT_DATA_SESSION_STATE_CHANGED: {
-			auto const &state_event
-			    = *reinterpret_cast<XrEventDataSessionStateChanged const *>(
-			        &event);
+			auto const &state_event {
+				*reinterpret_cast<XrEventDataSessionStateChanged const *>(
+				    &event)
+			};
 			m_openxr->session_state = state_event.state;
 			if (state_event.state == XR_SESSION_STATE_READY
 			    && !m_openxr->session_running) {
@@ -1461,7 +1791,7 @@ auto Application::render_openxr_frame(
 	XrViewState view_state {};
 	view_state.type = XR_TYPE_VIEW_STATE;
 	view_state.next = nullptr;
-	uint32_t view_count = static_cast<uint32_t>(m_openxr->views.size());
+	auto view_count { static_cast<uint32_t>(m_openxr->views.size()) };
 	view_count = std::min(
 	    view_count, static_cast<uint32_t>(m_openxr->swapchains.size()));
 	if (XR_FAILED(xrLocateViews(m_openxr->session, &locate_info, &view_state,
@@ -1469,6 +1799,8 @@ auto Application::render_openxr_frame(
 		return false;
 	}
 
+	update_hands(frame_state.predictedDisplayTime);
+
 	std::vector<XrCompositionLayerProjectionView> projection_views(view_count);
 	for (auto &projection_view : projection_views) {
 		projection_view = XrCompositionLayerProjectionView {};
@@ -1476,8 +1808,8 @@ auto Application::render_openxr_frame(
 		projection_view.next = nullptr;
 	}
 	for (uint32_t i = 0; i < view_count; ++i) {
-		auto &swapchain = m_openxr->swapchains[i];
-		uint32_t image_index = 0;
+		auto const &swapchain { m_openxr->swapchains[i] };
+		uint32_t image_index { 0 };
 		XrSwapchainImageAcquireInfo acquire_info {};
 		acquire_info.type = XR_TYPE_SWAPCHAIN_IMAGE_ACQUIRE_INFO;
 		acquire_info.next = nullptr;
@@ -1522,8 +1854,9 @@ auto Application::render_openxr_frame(
 	layer.viewCount = view_count;
 	layer.views = projection_views.data();
 
-	XrCompositionLayerBaseHeader const *layers[]
-	    = { reinterpret_cast<XrCompositionLayerBaseHeader *>(&layer) };
+	XrCompositionLayerBaseHeader const *layers[] {
+		reinterpret_cast<XrCompositionLayerBaseHeader *>(&layer)
+	};
 	XrFrameEndInfo end_info {};
 	end_info.type = XR_TYPE_FRAME_END_INFO;
 	end_info.next = nullptr;
@@ -1536,12 +1869,13 @@ auto Application::render_openxr_frame(
 
 auto Application::update_camera_from_xr_view(XrView const &view) -> void
 {
-	auto const &pose = view.pose;
-	smath::Vec3 position { pose.position.x, pose.position.y, pose.position.z };
-	auto forward
-	    = xr_rotate_vector(pose.orientation, smath::Vec3 { 0.0f, 0.0f, -1.0f });
-	auto up
-	    = xr_rotate_vector(pose.orientation, smath::Vec3 { 0.0f, 1.0f, 0.0f });
+	auto const &pose { view.pose };
+	smath::Vec3 const position { pose.position.x, pose.position.y,
+		pose.position.z };
+	auto const forward { xr_rotate_vector(
+		pose.orientation, smath::Vec3 { 0.0f, 0.0f, -1.0f }) };
+	auto const up { xr_rotate_vector(
+		pose.orientation, smath::Vec3 { 0.0f, 1.0f, 0.0f }) };
 	m_camera.position = position;
 	m_camera.target = position + forward;
 	m_camera.up = up;
@@ -1549,6 +1883,106 @@ auto Application::update_camera_from_xr_view(XrView const &view) -> void
 	m_cursor = PolarCoordinate::from_vec3(m_camera.target - m_camera.position);
 }
 
+auto Application::update_hands(XrTime display_time) -> void
+{
+	if (!m_openxr || !m_openxr->hand_tracking_supported) {
+		m_left_hand_valid = false;
+		m_right_hand_valid = false;
+		return;
+	}
+
+	if (m_openxr->left_hand_tracker != XR_NULL_HANDLE
+	    && m_openxr->locate_hand_joints) {
+		XrHandJointsLocateInfoEXT locate_info {};
+		locate_info.type = XR_TYPE_HAND_JOINTS_LOCATE_INFO_EXT;
+		locate_info.next = nullptr;
+		locate_info.baseSpace = m_openxr->app_space;
+		locate_info.time = display_time;
+
+		XrHandJointLocationEXT locations[XR_HAND_JOINT_COUNT_EXT];
+		XrHandJointLocationsEXT locations_info {};
+		locations_info.type = XR_TYPE_HAND_JOINT_LOCATIONS_EXT;
+		locations_info.next = nullptr;
+		locations_info.jointCount = XR_HAND_JOINT_COUNT_EXT;
+		locations_info.jointLocations = locations;
+
+		if (XR_SUCCEEDED(m_openxr->locate_hand_joints(
+		        m_openxr->left_hand_tracker, &locate_info, &locations_info))) {
+			m_left_hand_valid = (locations[0].locationFlags
+			                        & XR_SPACE_LOCATION_POSITION_VALID_BIT)
+			    != 0;
+			if (m_left_hand_valid) {
+				for (uint32_t j { 0 }; j < XR_HAND_JOINT_COUNT_EXT; j++) {
+					m_left_joints[j]
+					    = smath::Vec3 { locations[j].pose.position.x,
+						      locations[j].pose.position.y,
+						      locations[j].pose.position.z };
+				}
+			}
+		} else {
+			m_left_hand_valid = false;
+		}
+	}
+
+	if (m_openxr->right_hand_tracker != XR_NULL_HANDLE
+	    && m_openxr->locate_hand_joints) {
+		XrHandJointsLocateInfoEXT locate_info {};
+		locate_info.type = XR_TYPE_HAND_JOINTS_LOCATE_INFO_EXT;
+		locate_info.next = nullptr;
+		locate_info.baseSpace = m_openxr->app_space;
+		locate_info.time = display_time;
+
+		XrHandJointLocationEXT locations[XR_HAND_JOINT_COUNT_EXT];
+		XrHandJointLocationsEXT locations_info {};
+		locations_info.type = XR_TYPE_HAND_JOINT_LOCATIONS_EXT;
+		locations_info.next = nullptr;
+		locations_info.jointCount = XR_HAND_JOINT_COUNT_EXT;
+		locations_info.jointLocations = locations;
+
+		if (XR_SUCCEEDED(m_openxr->locate_hand_joints(
+		        m_openxr->right_hand_tracker, &locate_info, &locations_info))) {
+			m_right_hand_valid = (locations[0].locationFlags
+			                         & XR_SPACE_LOCATION_POSITION_VALID_BIT)
+			    != 0;
+			if (m_right_hand_valid) {
+				for (uint32_t j { 0 }; j < XR_HAND_JOINT_COUNT_EXT; j++) {
+					m_right_joints[j]
+					    = smath::Vec3 { locations[j].pose.position.x,
+						      locations[j].pose.position.y,
+						      locations[j].pose.position.z };
+				}
+			}
+		} else {
+			m_right_hand_valid = false;
+		}
+	}
+}
+
+auto Application::render_hands(
+    VulkanRenderer::GL &gl, smath::Mat4 const &view_projection) -> void
+{
+	gl.set_texture(&m_renderer->white_texture());
+	auto constexpr radius { 0.005f };
+
+	if (m_left_hand_valid) {
+		for (uint32_t j { 0 }; j < XR_HAND_JOINT_COUNT_EXT; j++) {
+			auto const &pos { m_left_joints[j] };
+			gl.set_transform(view_projection * smath::translate(pos));
+			gl.draw_sphere(smath::Vec3 { 0.0f, 0.0f, 0.0f }, radius, 8, 16,
+			    smath::Vec4 { 1.0f, 0.0f, 0.0f, 1.0f });
+		}
+	}
+
+	if (m_right_hand_valid) {
+		for (uint32_t j { 0 }; j < XR_HAND_JOINT_COUNT_EXT; j++) {
+			auto const &pos { m_right_joints[j] };
+			gl.set_transform(view_projection * smath::translate(pos));
+			gl.draw_sphere(smath::Vec3 { 0.0f, 0.0f, 0.0f }, radius, 8, 16,
+			    smath::Vec4 { 1.0f, 0.0f, 0.0f, 1.0f });
+		}
+	}
+}
+
 auto Application::process_libinput_events() -> void
 {
 	if (!m_libinput)

src/Application.h

@@ -13,6 +13,8 @@
 #include <linux/input-event-codes.h>
 #include <openxr/openxr.h>
 
+#include "smath.hpp"
+
 #include "Loader.h"
 #include "Logger.h"
 #include "Skybox.h"
@@ -73,6 +75,9 @@ private:
 	    std::function<void(VulkanRenderer::GL &)> const &record,
 	    float dt_seconds) -> bool;
 	auto update_camera_from_xr_view(XrView const &view) -> void;
+	auto update_hands(XrTime display_time) -> void;
+	auto render_hands(
+	    VulkanRenderer::GL &gl, smath::Mat4 const &view_projection) -> void;
 
 	SDL_Window *m_window { nullptr };
 	Backend m_backend { Backend::SDL };
@@ -104,6 +109,13 @@ private:
 
 	Camera m_camera;
 	PolarCoordinate m_cursor;
+
+	static inline std::array<smath::Vec3, XR_HAND_JOINT_COUNT_EXT>
+	    m_left_joints {};
+	static inline std::array<smath::Vec3, XR_HAND_JOINT_COUNT_EXT>
+	    m_right_joints {};
+	static inline bool m_left_hand_valid { false };
+	static inline bool m_right_hand_valid { false };
 };
 
 } // namespace Lunar

src/VulkanRenderer.cpp

@@ -426,37 +426,66 @@ auto VulkanRenderer::GL::draw_sphere(smath::Vec3 center, float radius,
 	if (sphere_color.has_value())
 		color(*sphere_color);
 
+	begin(GeometryKind::Triangles);
+
 	for (int y = 0; y < rings; y++) {
-		float const v = static_cast<float>(y + 1) / static_cast<float>(rings);
+		float const v1 = static_cast<float>(y) / static_cast<float>(rings);
+		float const v2 = static_cast<float>(y + 1) / static_cast<float>(rings);
 
-		float const theta = v * pi;
+		float const theta1 = v1 * pi;
+		float const theta2 = v2 * pi;
 
-		float const s = std::sin(theta);
-		float const c = std::cos(theta);
+		float const s1 = std::sin(theta1);
+		float const c1 = std::cos(theta1);
+		float const s2 = std::sin(theta2);
+		float const c2 = std::cos(theta2);
 
-		begin(GeometryKind::TriangleStrip);
-
-		for (int x = 0; x <= segments; x++) {
-			float const u
+		for (int x = 0; x < segments; x++) {
+			float const u1
 			    = static_cast<float>(x) / static_cast<float>(segments);
-			float const phi = u * (2.0f * pi);
+			float const u2
+			    = static_cast<float>(x + 1) / static_cast<float>(segments);
 
-			float const sp = std::sin(phi);
-			float const cp = std::cos(phi);
+			float const phi1 = u1 * (2.0f * pi);
+			float const phi2 = u2 * (2.0f * pi);
 
-			// Vertex on ring y+1
-			{
-				smath::Vec3 n { s * cp, c, s * sp };
-				normal(n);
-				uv(smath::Vec2 { u, 1.0f - v });
+			float const sp1 = std::sin(phi1);
+			float const cp1 = std::cos(phi1);
+			float const sp2 = std::sin(phi2);
+			float const cp2 = std::cos(phi2);
 
-				smath::Vec3 p { center + n * radius };
-				vert(p);
+			smath::Vec3 n1 { s1 * cp1, c1, s1 * sp1 };
+			smath::Vec3 n2 { s1 * cp2, c1, s1 * sp2 };
+			smath::Vec3 n3 { s2 * cp1, c2, s2 * sp1 };
+			smath::Vec3 n4 { s2 * cp2, c2, s2 * sp2 };
+
+			normal(n1);
+			uv(smath::Vec2 { u1, 1.0f - v1 });
+			vert(center + n1 * radius);
+
+			normal(n2);
+			uv(smath::Vec2 { u2, 1.0f - v1 });
+			vert(center + n2 * radius);
+
+			normal(n3);
+			uv(smath::Vec2 { u1, 1.0f - v2 });
+			vert(center + n3 * radius);
+
+			normal(n2);
+			uv(smath::Vec2 { u2, 1.0f - v1 });
+			vert(center + n2 * radius);
+
+			normal(n4);
+			uv(smath::Vec2 { u2, 1.0f - v2 });
+			vert(center + n4 * radius);
+
+			normal(n3);
+			uv(smath::Vec2 { u1, 1.0f - v2 });
+			vert(center + n3 * radius);
 		}
 	}
 
 	end();
-	}
 }
 
 auto VulkanRenderer::GL::draw_mesh(GPUMeshBuffers const &mesh,
@@ -910,19 +939,35 @@ auto VulkanRenderer::setup_kms_surface() -> void
 		throw std::runtime_error("App init fail");
 	}
 
+	m_logger.info("Found {} Vulkan physical device(s)", devices.size());
+
 	for (auto const &device : devices) {
+		auto const props = device.getProperties();
+		m_logger.info("Checking device: {}", std::string(props.deviceName));
+
 		auto const displays = device.getDisplayPropertiesKHR();
 		if (displays.empty()) {
+			m_logger.info("  Device has no display properties");
 			continue;
 		}
 
+		m_logger.info("  Device has {} display(s)", displays.size());
+
 		for (auto const &display_props : displays) {
+			m_logger.info("  Checking display: {}",
+			    display_props.displayName
+			        ? std::string(display_props.displayName)
+			        : "(unnamed)");
+
 			auto const modes
 			    = device.getDisplayModePropertiesKHR(display_props.display);
 			if (modes.empty()) {
+				m_logger.info("    Display has no modes");
 				continue;
 			}
 
+			m_logger.info("    Display has {} mode(s)", modes.size());
+
 			auto const best_mode_it = std::max_element(modes.begin(),
 			    modes.end(), [](auto const &lhs, auto const &rhs) {
 				    auto const lhs_extent = lhs.parameters.visibleRegion;
@@ -955,9 +1000,15 @@ auto VulkanRenderer::setup_kms_surface() -> void
 				}
 			}
 			if (!plane_index) {
+				m_logger.info("    No display plane supports this display ({} "
+				              "plane(s) checked)",
+				    planes.size());
 				continue;
 			}
 
+			m_logger.info(
+			    "    Found suitable display on plane {}", *plane_index);
+
 			auto const extent = best_mode_it->parameters.visibleRegion;
 			KmsState state {};
 			state.display = display_props.display;
@@ -1097,13 +1148,17 @@ auto VulkanRenderer::vk_init() -> void
 		VK_KHR_COPY_COMMANDS_2_EXTENSION_NAME,
 		VK_KHR_BUFFER_DEVICE_ADDRESS_EXTENSION_NAME,
 	};
+	std::vector<char const *> required_extensions {};
 	for (auto const &extension : m_extra_device_extensions) {
-		desired_extensions.push_back(extension.c_str());
+		required_extensions.push_back(extension.c_str());
 	}
 	phys_device_selector.set_surface(m_vk.surface)
 	    .add_desired_extensions(desired_extensions)
 	    .set_required_features_13(features_13)
 	    .add_required_extension_features(buffer_device_address_features);
+	if (!required_extensions.empty()) {
+		phys_device_selector.add_required_extensions(required_extensions);
+	}
 	auto physical_device_selector_return { phys_device_selector.select() };
 	if (!physical_device_selector_return) {
 		std::println(std::cerr,