Abra

Abra is a modern rendering engine built on OpenGL, featuring a flexible hybrid Forward + Deferred pipeline. It’s designed for clarity, experimentation, and real-time graphics research.

Features

• Hybrid Forward / Deferred Pipeline
  • Deferred path is fully G-Buffer based, or you can switch to Forward anytime.
• Opaque & Transparent Rendering
  • Opaque objects go through Deferred or Forward (depending on your selected pipeline). Transparent objects always render in the Forward pipeline to keep blending sane.
• Instanced Rendering (GPU Instancing)
  • Efficiently draw many copies of the same mesh in a single draw call.
• Lighting & Shadows
  • Directional Light + Shadow Mapping
  • Point Light + Shadow Mapping (cubemap-based)
  • Spot Light + Shadow Mapping
• HDR Rendering
  • Full HDR workflow with tone mapping and manual exposure control.
• PBR
  • Image-based Lighting (IBL) with prefiltered environment cubemaps.
  • Load-time diffuse & specular irradiance cubemap convolution.
• SSAO
  • Only avaliable in the deferred pipeline.
• Frustum Culling
  • Per-entity and per-mesh culling.
• Skybox Rendering
• Advanced Materials
  • Normal Mapping
  • Parallax Mapping
• Anti-Aliasing
  • MSAA (only avaliable in the forward pipeline)
  • FXAA
• Post-Processing
  • Modular, extendable post-FX chain (bloom, blur, tone mapping, gamma, etc.)
• Entity Component System (ECS)
  • Data-oriented architecture for flexible, efficient game objects.
• Debug Tools
  • Normal visualization
  • Wireframe mode
• Tessellation Pipeline
  • Terrain rendering with dynamic LOD
• Built-in Models
  • Cube – perfect for testing transforms, lighting, and shadow maps
  • Cubemap – used for skybox rendering
  • Plane
  • Sphere
  • Terrain
  • Screen Quad – for post-processing, deferred pipeline, and blitting
• Supported Model Format
  • Abra currently supports glTF 2.0 models only.Other formats (e.g., OBJ, FBX) are not supported.
• PBR Workflow
  • The engine follows the glTF metallic-roughness workflow.
  • Texture Conventions
    • Albedo (Base Color)
      • sRGB
    • Normal Map
      • Linear
    • Roughness-Metallic (packed)
      • Linear
      • Channels:
        • R → unused
        • G → Roughness
        • B → Metallic
    • Occlusion Map
      • Linear
      • Channels:
        • R → AO
      • Optionally AO can be baked into the Roughness-Metallic texture.

Screenshots

Controls

Key	Action
WASD	Move
RMB	enable/disable Free Look

RUN

➜  ~ ./abra scene_Sponza_Spotlight.json

Roadmap

• Cascaded shadow maps

License

This project is licensed under the BSD 3-Clause License. See the LICENSE file for details.