Space — C++ OpenGL PBR Renderer

A real-time 3D rendering engine built with C++ and OpenGL, inspired by the architecture of Three.js.

Features

Rendering

• PBR — Cook-Torrance BRDF (GGX NDF, Smith Geometry, Schlick Fresnel)
• IBL — Image-Based Lighting with HDR environment map (diffuse irradiance + specular split-sum)
• ACESFilmic Tone Mapping — filmic contrast, no blown-out highlights
• Normal Mapping — tangent-space TBN with Gram-Schmidt re-orthogonalization
• MSAA — multi-sample anti-aliasing via offscreen FBO resolve
• Alpha Blending — two-pass opaque + transparent with correct depth write handling

glTF 2.0 Support

• Native GLTFLoader — parses glTF/GLB directly without Assimp (spec-compliant)
• KHR_materials_clearcoat — dual-layer specular (hair, car paint, coated surfaces)
• KHR_materials_specular — Fresnel F0 tint and intensity override
• Full PBR material — albedo, metallic-roughness, normal, occlusion, emissive textures
• Alpha modes — OPAQUE / MASK / BLEND per material
• Double-sided geometry support

Architecture

• IRenderer abstract interface — OpenGL backend today, Vulkan-ready tomorrow
• Scene graph — Object3D / MeshObject / SceneObject hierarchy
• GLTFLoader — pimpl pattern hides nlohmann/json; direct GPU texture IDs
• GLIBL — precomputes irradiance cubemap (32px), prefiltered env map (128px, 5 mips), BRDF LUT (512px) on GPU

Developer Tools

• ImGui debug panel — model selector, PBR sliders, light position/intensity, IBL intensity, fullscreen toggle
• Headless screenshot — --screenshot [path] saves PNG via glReadPixels, no display required

Project Structure

src/
├── core/         # Object3D, MeshObject, SceneObject, Camera, Geometry, Material
├── renders/      # GLRenderer, GLProgram, GLTexture, GLBindingState, GLIBL, GLFramebuffer
├── loaders/      # GLTFLoader (native glTF 2.0), ObjLoader (Assimp)
└── errors/       # OpenGL error helpers
shaders/
├── pbr_shader.{vs,fs}              # Main PBR + IBL shader
├── equirect_to_cubemap.{vs,fs}     # HDR equirectangular → cubemap
├── irradiance_convolution.{vs,fs}  # Diffuse IBL precomputation
├── prefilter.{vs,fs}               # Specular IBL precomputation
└── brdf_lut.{vs,fs}                # Smith GGX BRDF LUT
assets/
├── env/neutral.hdr                 # Studio HDR environment map
└── lily/                           # Stellar Blade - Lily GLB model
deps/
├── glad/          # OpenGL loader
├── glm/           # Math library
├── imgui/         # Dear ImGui
├── nlohmann/      # JSON parser (for GLTFLoader)
└── stab/          # stb_image + stb_image_write

Requirements

• macOS (Apple Silicon / Intel)
• CMake ≥ 3.5
• C++17

brew install cmake glog assimp sdl2

Build & Run

git clone https://github.com/lele94218/space.git
cd space
cmake . -DCMAKE_POLICY_VERSION_MINIMUM=3.5
make -j4
./main

Headless screenshot (no display needed)

./main --screenshot output.png

Controls

Input	Action
Mouse drag	Orbit camera
Scroll	Zoom
F	Toggle fullscreen
Q / ESC	Quit

Roadmap

• Skeletal animation (glTF skins + AnimationMixer)
• Shadow mapping
• Skybox (render IBL env as background)
• Skin subsurface scattering (SSS)
• Morph targets (blend shapes / facial animation)
• Post-processing (Bloom, SSAO, DoF)
• Multiple light sources

Commit History

Commit	Feature
a7770d1	IRenderer abstract interface
34b65f3	Normal mapping (TBN)
5af61c3	PBR (Cook-Torrance BRDF)
354d0ae	Native GLTFLoader
ba52477	Fullscreen, Lily auto-load, PBR defaults
917903f	Camera/light defaults
6a36649	KHR clearcoat/specular, headless screenshot
e8d47cb	IBL, ACESFilmic, hair depth fix, color correction