Overview

This sample demonstrates the essential patterns of a Lysa Engine application: loading a 3D asset from a .assets pack file, displaying it through the deferred renderer with lights and post-processing, and animating it with a continuous, frame-rate-independent Y-axis rotation.

The tutorial source code is available at https://github.com/LysaEngine/lysa_tutorial_01.

Engine architecture at a glance

Lysa is built on top of the Vireo Rendering Hardware Interface (RHI), which abstracts Vulkan and DirectX 12 behind a single API. Lysa adds the engine layer: asset management, scene representation, a deferred (or forward) rendering pipeline, post-processing, physics integration, and an event bus.

The three foundational objects in every application are:

Object	Type	Role
Context	`lysa::Context`	Singleton that owns every engine subsystem
Lysa runtime	`lysa::Lysa`	Initialises the context and runs the main loop
Render target	`lysa::RenderTarget`	Owns the swapchain and drives per-frame rendering

lysa::ctx() is a free function that returns a reference to the singleton Context. Every subsystem is reachable through it:

Member	Type	Purpose
`ctx().events`	`lysa::EventManager`	Publish/subscribe event bus
`ctx().fs`	`lysa::VirtualFS`	`app://` and `user://` virtual filesystems
`ctx().res`	`lysa::ResourcesRegistry`	Registry of GPU resource managers
`ctx().vireo`	`vireo::Vireo`	Raw RHI device and resource factory
`ctx().defer`	`lysa::DeferredTasksBuffer`	Queue a lambda for execution on the next frame
`ctx().threads`	`lysa::AsyncTasksPool`	Thread pool for background CPU work
`ctx().config`	`lysa::ContextConfiguration`	Read-only copy of the startup configuration

Main loop events

The engine fires three events every iteration:

Event	Payload	Rate
`lysa::MainLoopEvent::PHYSICS_PROCESS`	`double delta` (seconds)	Fixed, default 1/60 s per step (configurable via `lysa::ContextConfiguration`), fired multiple times per frame if needed
`lysa::MainLoopEvent::PROCESS`	`double alpha` (seconds)	Once per rendered frame, variable
`lysa::MainLoopEvent::QUIT`	none	Once, just before resources are destroyed

PHYSICS_PROCESS uses a fixed timestep so that physics simulations remain deterministic regardless of frame rate. PROCESS receives the remaining fractional time and is where you advance game logic and submit the frame.

Source files

File	Role
`src/Main.cpp`	`Application` class and `lysaMain` entry point
`src/MainWindow.ixx`	Window and renderer configuration
`src/SceneInstance.ixx/.cpp`	Scene node hierarchy and asset loading
`src/SceneTree.ixx/.cpp`	`lysa::Scene` wrapper with process callbacks
`src/Camera.ixx/.cpp`	First-person fly camera
`src/RotatingAssetScene.ixx/.cpp`	Sample-specific scene logic