VRI

An extensible render hardware interface for Vulkan, D3D12, Metal, WebGPU, and the OpenGL family — plus CPU software rendering — with a stable C ABI core and a C++23 wrapper.

zzxzzk115/VRI - GitHub

Part of the Vultra Ecosystem.

Why This Exists

VRI was born out of disappointment with every existing cross-platform RHI I tried:

  • bgfx abstracts graphics through OpenGL state-machine thinking — a relic of an older era that forfeits the advanced features of modern explicit APIs.
  • Diligent Engine and The Forge don’t fully cover the backend matrix, and neither leverages Slang to compile a single shader source to every shading backend.
  • NRI supports only Vulkan and DirectX.
  • None of them consider OpenXR — a dealbreaker when your research is VR rendering.

So I wrote the RHI that satisfies my own requirements while pushing for the broadest platform coverage I can achieve: one explicit, modern API (command buffers, descriptor sets, explicit synchronization) over Vulkan, D3D12, Metal, WebGPU, OpenGL / GLES / WebGL 2, and even CPU software rendering.

Design Decisions

A C ABI core with a header-only C++23 wrapper. The C ABI exists for two reasons: it makes P/Invoke bindings for C# — and bindings for any other language — straightforward, and it guarantees ABI stability across compilers and versions. Day-to-day ergonomics come from the modern C++23 wrapper on top.

Software rendering is a feature, not a fallback. Built-in SwiftShader / Mesa backends let the full test suite run on GPU-less CI machines, and cover the genuinely GPU-less edge cases I refuse to ignore.

Single-source shaders. Shaders are authored in Slang and compiled offline to each backend’s bytecode — no per-API shader forks.

OpenXR from day one. XR support is already available as a VRI extension; the deeper integration (stereo swapchains, session plumbing) lives one layer up, in VRI-Framework.

A built-in validation layer and diagnostics sink keep multi-backend debugging sane.

Proof It Works

Lazy-100, a complete fantasy game console with an in-console editor suite, runs entirely on VRI — on desktop and in the browser.

Looking Ahead

VRI is the designated rendering foundation of the entire ecosystem: libvultra will migrate its rendering core onto VRI via VRI-Framework, and the stable C ABI is the on-ramp for the planned CoreCLR (C#) engine architecture.