Simple3D

Simple3D is a clean, minimalistic 3D/2D game framework for C++23 and Lua. It wraps an Urho3D engine fork with a high-level, game-first API that exposes no engine internals. Subclass Game, override Start() and Update(), and ship — without needing to know anything about Urho3D's component model.

Urho3D types (Urho3D::Node, Urho3D::Scene, Urho3D::Application) never appear in public headers. They are hidden behind PIMPL classes. The only exception is math primitives (Vector2/3/4, Color, Quaternion, Matrix3/3x4/4, BoundingBox, Rect) which are re-exported as Simple3D:: type aliases.

Architecture

Game Code (C++ / Lua)
        ↓
   Simple3D API          ← stable public boundary; no engine types visible here
        ↓
  Urho3D fork (U3D)      ← scene graph, physics, navigation, networking, Lua
        ↓
  XNA C++ runtime        ← rendering, audio, input  (Nova3D backend only)
        ↓
  Vulkan / GLES / bgfx   ← GPU backends
        ↓
  SDL3 / OS              ← windowing, events

Quick start (C++)

#include <Simple3D/Simple3D.h>
using namespace Simple3D;

class MyGame : public Game {
public:
    Entity* player;
    Camera* camera;

    void Start() override {
        auto ground = CreateEntity("Ground");
        ground->AddModel("models/ground.obj");
        ground->AddRigidBody(0.0f);
        ground->AddBoxCollider(Vector3(50, 1, 50));

        player = CreateEntity("Player");
        player->AddModel("models/character.fbx");
        player->AddAnimationController();
        player->AddRigidBody(1.0f);
        player->AddCapsuleCollider(0.5f, 1.8f);
        player->SetPosition(0, 2, 0);
        player->AddScript("Scripts/player.lua");

        camera = CreateCamera();
        camera->Follow(player, 6.0f);
        camera->SetSmoothFollow(true);

        PlayMusic("Music/theme.ogg");
    }

    void Update(float dt) override {
        if (IsKeyDown(Key::Escape)) Quit();
    }
};

int main() {
    return CreateGame<MyGame>()->Run();
}

Lua scripting

Per-entity .lua scripts with Start(), Update(dt), and Stop(). Hot-reloadable at runtime without recompiling the engine.

-- Scripts/player.lua
speed = 6
jumpForce = 8

function Update(dt)
    local move = Vector3(0, 0, 0)
    if Input:IsKeyDown("W") then move.z = move.z + 1 end
    if Input:IsKeyDown("S") then move.z = move.z - 1 end
    if Input:IsKeyDown("A") then move.x = move.x - 1 end
    if Input:IsKeyDown("D") then move.x = move.x + 1 end

    if move:Length() > 0 then
        entity:MoveRelative(move:Normalized() * speed * dt)
        entity:GetAnimationController():Play("run")
    else
        entity:GetAnimationController():Play("idle")
    end

    if Input:IsKeyPressed("Space") and entity:IsOnGround() then
        entity:ApplyImpulse(Vector3(0, jumpForce, 0))
        PlaySound("Sounds/jump.wav")
    end
end

Module status

Build

Prerequisites

• CMake 3.21+
• C++23 compiler (GCC 13+, Clang 16+, MSVC 2022+)
• U3D built at /rv/data/library/github.com/u3d-community/U3D/cmake-build-debug (or set URHO3D_HOME / U3D_HOME)

U3D backend (default)

cmake -S . -B build-u3d
cmake --build build-u3d

Nova3D backend

cmake -S . -B build-nova3d -DSIMPLE3D_ENGINE=NOVA3D
cmake --build build-nova3d

Web (Emscripten)

emcmake cmake -S . -B build-web -DSIMPLE3D_ENGINE=U3D
cmake --build build-web

Windows (MinGW cross-compile)

cmake -S . -B build-windows \
  -DCMAKE_TOOLCHAIN_FILE=cmake/toolchains/mingw-w64.cmake \
  -DSIMPLE3D_ENGINE=U3D
cmake --build build-windows

Platforms

Windows, Linux, macOS (via U3D + SDL 3). Android (Task #8, Nova3D backend). Web/Emscripten (Task #9).

Attribution

Simple3D is built on top of the Urho3D / U3D engine fork (MIT license). Math types are ABI-identical re-exports of Urho3D math. All adapted files carry the original Urho3D copyright notice.

Copyright (c) 2008–2022 the Urho3D project. Copyright (c) 2024–2026 Robert Vokac and the Simple3D contributors.