Rendering Engine

A cross-platform 3D/2D rendering engine written in Rust using OpenGL / OpenGL ES through glow.

The goal of this project is to build a lightweight, modular, and flexible rendering library crate (rendering_engine) that runs seamlessly across desktop and mobile while utilizing modern rendering techniques (Multi-Draw Indirect, persistent mapped buffers, multi-threaded rendering, texture management, FBOs, compute shaders, and skybox passes).

---

🌟 Features

• Modular Architecture (core, resources, render)

  • Clean separation between low-level memory/buffers, graphics resources, and rendering pipelines.

• Indirect Draw Batching

  • Groups instances by material and mesh and submits indirect draw commands.
  • The current glow path dispatches those commands with a GL-call loop; the buffer layout is ready for native MDI when the backend exposes it.
  • Uses GPU-side instance data handling to avoid unnecessary CPU-to-GPU synchronization.

• Textures, Atlases & Texture Arrays

  • 2D, cubemap, and array textures; sRGB and BC1/BC4/BC5 uploads; CPU RGBA8 atlas packing and UV helpers.

• Offscreen Framebuffers & Render Targets

  • FBO abstractions (Framebuffer) with color attachments, depth textures, and depth renderbuffers.

• Compute Shader Pipelines

  • ComputeShader support for OpenGL ES 3.1+ / OpenGL 4.3+.

• Fullscreen Skybox Pass

  • Pre-pass skybox pipeline with LEQUAL depth testing and inverse view-projection uniform upload.

• Dedicated Screen-Space UI

  • Pixel-coordinate draw list with its own shader and buffers, separate from scene meshes and camera transforms.

• Light Uniform Block

  • Renderer-managed std140 UBO for up to 16 directional, point, or spot lights.
  • Shaders opt into the shared block layout; the demo uses it for diffuse lighting.

• Persistent Mapped Buffers

  • Uses persistent mapped SSBOs with multiple fenced regions (TRANSFORM_REGIONS) to safely update GPU data while avoiding CPU/GPU conflicts.

• Dedicated Render Thread & Triple-Buffer Handoff

  • Game logic and rendering exchange the latest frame through clone-free slot swaps. The GL context and Renderer are created and used only on the render thread.

• Frame Diagnostics

  • Per-frame counts for submitted and culled instances, draw calls, pipeline changes, and estimated triangles.

• Desktop and Android Support

  • Desktop support through winit / glutin.
  • Android support through android-native-activity and OpenGL ES.

---

📁 Repository Structure

rendering-engine/
├── engine/                 # Core rendering engine crate (`rendering_engine`)
│   └── src/
│       ├── lib.rs
│       ├── core/           # Memory allocators, persistent buffers, math & triple buffer
│       ├── render/         # Rendering APIs, frame data, passes, scene graph
│       │   └── renderer/   # Scene API, resources, passes, sync, world and draw submission
│       ├── resources/      # GPU resources and resource managers
│       │   ├── shader/     # Shader program and manager
│       │   └── texture/    # Texture formats, atlas, and manager
│
├── demo/                   # Animated Ava model application
│   └── src/
│
├── docs/                   # Library documentation & guides
│   └── USAGE.md            # Simple, comprehensive library usage guide
│
└── shaders_gles/           # OpenGL / OpenGL ES shader sources

---

📖 Documentation & Library Usage

For code examples on using rendering_engine as a library crate in your own projects, see Library Usage Guide.

---

🚀 Getting Started

Building & Running Desktop Demo

To launch the desktop demo application:

cargo run --bin desktop

Controls (Demo)

• Left drag: orbit the camera.
• Right drag: pan the camera.
• Mouse wheel: zoom.
• F: fit the model in view.
• Space: pause or resume animation.
• R: restart the current clip.
• 1–9: select an animation clip.
• E: toggle vertical sync.
• G: toggle wireframe.

The demo loads models/Ava.glb, displays its scene hierarchy and PBR base color, and plays its skeletal animation through the engine's normal mesh, material, frame handoff, lighting, and rendering paths. cargo run -p demo --bin desktop -- --inspect-model parses Ava and prints mesh, skin, and clip details without opening a window. See Asset pipeline notes for implemented formats and current limits.

---

📜 License

This project is open-source and available under the BSD-3-Clause License.