CryoGen

Vulkan game engine featuring real-time physically-based rendering, hardware ray tracing (VK_KHR_ray_tracing_pipeline), an impulse-based rigid-body solver, an authoritative-server multiplayer stack built on Boost.Asio, an ImGui-driven level editor, and Assimp-backed mesh loading.

                       ┌──────────────────────────────┐
                       │        apps/editor           │  ImGui level editor
                       │        apps/runtime          │  Standalone client
                       │        apps/server           │  Headless server
                       └────────────────┬─────────────┘
                                        │
                       ┌────────────────┴─────────────┐
                       │      cryogen (static lib)    │
                       │ ┌──────────┬──────────────┐  │
                       │ │  render  │   physics    │  │
                       │ │  ECS     │   net (Asio) │  │
                       │ │  scene   │   editor     │  │
                       │ │  assets  │   input      │  │
                       │ └──────────┴──────────────┘  │
                       └────────────────┬─────────────┘
                                        │
            Vulkan 1.2 ─ KHR_RT ─ SDL2 ─ GLFW ─ ImGui ─ Assimp ─ Boost.Asio

Feature matrix

System	Implementation
Windowing / input	SDL2 primary, GLFW secondary path, GLUT fallback
Renderer	Vulkan 1.2; forward PBR pass + KHR ray-tracing pipeline
Mesh loading	Assimp; positions / normals / tangents / UVs; PBR material extraction
Physics	Sequential-impulse rigid bodies, sphere/box/plane colliders, broadphase
Networking	Boost.Asio, authoritative server, snapshot replication, lag compensation
Editor	ImGui hierarchy + inspector + transform gizmo + scene save/load (JSON)
Scene serialization	nlohmann/json
ECS	Sparse-set component storage, archetype-free, deterministic iteration
Math	Header-only vec/mat/quat with SIMD-friendly layout

Building Cryogen

Prerequisites

Dependency	Minimum	Notes
C++ compiler	C++20	GCC 12, Clang 15, or MSVC 19.36+
CMake	3.22
Vulkan SDK	1.3.250+	Provides glslangValidator and validation layers
Boost	1.74	system component required (Asio header-only)
SDL2	2.0.20
GLFW	3.3	Secondary windowing path
FreeGLUT	optional	Legacy fallback for tooling
Assimp	5.2
ImGui	1.89+	Vendored — see third_party/README.md
nlohmann/json	3.11	Vendored
RenderDoc	optional	For GPU debugging

Linux (Ubuntu / Debian)

sudo apt install build-essential cmake ninja-build git \
  libsdl2-dev libglfw3-dev freeglut3-dev libassimp-dev \
  libboost-system-dev

# Vulkan SDK from LunarG, installed under /opt/vulkan
export VULKAN_SDK=/opt/vulkan/x86_64
export PATH=$VULKAN_SDK/bin:$PATH
export LD_LIBRARY_PATH=$VULKAN_SDK/lib:$LD_LIBRARY_PATH

git clone <this-repo> cryogen && cd cryogen
git submodule update --init    # vendors ImGui + nlohmann/json
cmake -S . -B build -G Ninja -DCMAKE_BUILD_TYPE=Release
cmake --build build -j
ctest --test-dir build --output-on-failure

macOS

Vulkan is provided by MoltenVK (shipped with the LunarG SDK). The KHR ray-tracing pipeline is not available on Metal; configure with -DCRYOGEN_ENABLE_RT=OFF to fall back to the PBR raster path only.

brew install cmake ninja boost sdl2 glfw assimp
# Install LunarG Vulkan SDK from https://vulkan.lunarg.com
cmake -S . -B build -G Ninja -DCMAKE_BUILD_TYPE=Release -DCRYOGEN_ENABLE_RT=OFF
cmake --build build -j

Windows (MSVC)

Use vcpkg to provide non-Vulkan dependencies:

vcpkg install boost-system sdl2 glfw3 assimp nlohmann-json --triplet x64-windows
cmake -S . -B build -DCMAKE_TOOLCHAIN_FILE=%VCPKG_ROOT%\scripts\buildsystems\vcpkg.cmake
cmake --build build --config Release

Build options

Option	Default	Description
CRYOGEN_BUILD_EDITOR	ON	Build the ImGui editor
CRYOGEN_BUILD_RUNTIME	ON	Build the standalone client
CRYOGEN_BUILD_SERVER	ON	Build the dedicated server
CRYOGEN_BUILD_TESTS	ON	Build unit tests
CRYOGEN_ENABLE_RT	ON	Compile the KHR ray tracing pipeline
CRYOGEN_ENABLE_VALIDATION	ON	Enable Vulkan validation layers in debug

Vendored dependencies

Run once after cloning:

mkdir -p third_party && cd third_party
git clone --depth 1 --branch v1.90.4 https://github.com/ocornut/imgui.git
git clone --depth 1 --branch v3.11.3 https://github.com/nlohmann/json.git

The CMake configuration will detect both automatically.

RenderDoc capture

Launch the editor or runtime client through RenderDoc with the working directory set to the build root so SPIR-V binaries resolve correctly:

$ renderdoccmd capture build/apps/runtime/cryogen_runtime

Troubleshooting

• glslangValidator not found — ensure $VULKAN_SDK/bin is on PATH.
• Validation errors about ray tracing — your GPU/driver may not expose VK_KHR_ray_tracing_pipeline; configure with -DCRYOGEN_ENABLE_RT=OFF.
• Boost.System link errors — install libboost-system-dev (Linux) or add boost-system to your vcpkg manifest.

Run

# Headless authoritative server
./build/apps/server/cryogen-server --tcp 27015 --udp 27016 --snap 30

# Client (offline)
./build/apps/runtime/cryogen-runtime

# Client (connect to server)
./build/apps/runtime/cryogen-runtime 127.0.0.1

# Editor
./build/apps/editor/cryogen-editor