Step 1: Create Project Directory Шаг 1: Создание директории проекта

Create a workspace folder and a new directory for your Box2D test project: Создайте рабочую папку для проектов и новую директорию для вашего тестового проекта Box2D:

Windows (Command Prompt / PowerShell)

mkdir C:\projects\box2d-test
cd C:\projects\box2d-test

Ubuntu (Terminal)

mkdir -p ~/projects/box2d-test
cd ~/projects/box2d-test

Step 2: Create Source Files (main.cpp & CMakeLists.txt) Шаг 2: Создание исходных файлов (main.cpp и CMakeLists.txt)

You can create these files using Notepad / Sublime Text on Windows, or nano in Ubuntu terminal: Вы можете создать эти файлы через Блокнот / Sublime Text в Windows или с помощью nano в терминале Ubuntu:

Windows (Terminal / Notepad)

notepad main.cpp
notepad CMakeLists.txt

Ubuntu (Terminal / Nano)

nano main.cpp
nano CMakeLists.txt

1. File Contents for main.cpp 1. Содержимое файла main.cpp

#include <box2d/box2d.h>
#include <iostream>

int main()
{
    std::cout << "Initializing Box2D v3 physics world..." << std::endl;

    // Create world definition and set gravity
    b2WorldDef worldDef = b2DefaultWorldDef();
    worldDef.gravity = (b2Vec2) { 0.0f, -9.8f };

    // Create physics world
    b2WorldId worldId = b2CreateWorld(&worldDef);

    // Create ground static body
    b2BodyDef groundBodyDef = b2DefaultBodyDef();
    groundBodyDef.position = (b2Vec2) { 0.0f, -10.0f };
    b2BodyId groundId = b2CreateBody(worldId, &groundBodyDef);

    // Attach ground box shape
    b2Polygon groundBox = b2MakeBox(50.0f, 10.0f);
    b2ShapeDef groundShapeDef = b2DefaultShapeDef();
    b2CreatePolygonShape(groundId, &groundShapeDef, &groundBox);

    // Create dynamic body
    b2BodyDef bodyDef = b2DefaultBodyDef();
    bodyDef.type = b2_dynamicBody;
    bodyDef.position = (b2Vec2) { 0.0f, 4.0f };
    b2BodyId bodyId = b2CreateBody(worldId, &bodyDef);

    // Attach dynamic box shape
    b2Polygon dynamicBox = b2MakeBox(1.0f, 1.0f);
    b2ShapeDef dynamicShapeDef = b2DefaultShapeDef();
    dynamicShapeDef.density = 1.0f;
    dynamicShapeDef.material.friction = 0.3f; // Or simply omit friction to use default shape settings

    // If using Box2D v3.0+, surface properties are set on the shape definition:
    b2CreatePolygonShape(bodyId, &dynamicShapeDef, &dynamicBox);

    // Prepare simulation parameters
    float timeStep = 1.0f / 60.0f;
    int subStepCount = 4;

    // Simulate 10 steps
    for (int i = 0; i < 10; ++i)
    {
        b2World_Step(worldId, timeStep, subStepCount);
        b2Vec2 position = b2Body_GetPosition(bodyId);
        b2Rot rotation = b2Body_GetRotation(bodyId);
        float angle = b2Rot_GetAngle(rotation);
        std::cout << "Step " << i + 1 << " -> Position: (" << position.x << ", " << position.y << ") Angle: " << angle << std::endl;
    }

    // Clean up world
    b2DestroyWorld(worldId);

    std::cout << "Box2D simulation finished successfully!" << std::endl;
    return 0;
}

2. File Contents for CMakeLists.txt 2. Содержимое файла CMakeLists.txt

Imports Box2D static library target explicitly and configures platform-specific paths: Явно импортирует цель статической библиотеки Box2D и настраивает пути под платформу:

set(CMAKE_BUILD_TYPE "Debug")

cmake_minimum_required(VERSION 3.21)
project(box2d_test CXX)

set(CMAKE_CXX_STANDARD 20)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

set(PROJECT_SOURCES
    main.cpp
)

add_executable(app)
target_sources(app PRIVATE ${PROJECT_SOURCES})

if(WIN32)
    set(BOX2D_DIR "C:/libs/box2d-3.1.1-mingw")

    target_include_directories(app PRIVATE
        ${BOX2D_DIR}/include
    )

    add_library(Box2D_Static STATIC IMPORTED)
    set_target_properties(Box2D_Static PROPERTIES
        IMPORTED_LOCATION "${BOX2D_DIR}/lib/libbox2d.a"
    )

    target_link_libraries(app PRIVATE
        Box2D_Static
    )

    # Strip symbols and optimize aggressive for size
    target_compile_options(app PRIVATE -Os)

    # MinGW static build settings
    target_link_options(app PRIVATE -static -s -static-libgcc -static-libstdc++)

    if (CMAKE_BUILD_TYPE STREQUAL "Debug")
        target_link_options(app PRIVATE -mconsole)
    else()
        target_link_options(app PRIVATE -mwindows)
    endif()

else() # Linux / Ubuntu
    set(BOX2D_DIR "$ENV{HOME}/libs/box2d-3.1.1-ubuntu")

    target_include_directories(app PRIVATE
        ${BOX2D_DIR}/include
    )

    add_library(Box2D_Static STATIC IMPORTED)
    set_target_properties(Box2D_Static PROPERTIES
        IMPORTED_LOCATION "${BOX2D_DIR}/lib/libbox2d.a"
    )

    find_package(Threads REQUIRED)

    target_link_libraries(app PRIVATE
        Box2D_Static
        Threads::Threads
    )
endif()

Step 3: Create Build & Execution Scripts Шаг 3: Создание скриптов сборки и запуска

Windows (MinGW / Batch Scripts)

config-exe.bat

cmake -G Ninja -S . -B dist/win

build-exe.bat

cmake --build dist/win

run-exe.bat

@echo off
.\dist\win\app.exe

Run the scripts sequentially in Command Prompt or PowerShell: Последовательно запустите скрипты в командной строке или PowerShell:

config-exe.bat
build-exe.bat
run-exe.bat

Ubuntu (Bash Scripts)

config-bin.sh

#!/usr/bin/env bash
set -e
cmake -G Ninja -S . -B dist/linux

build-bin.sh

#!/usr/bin/env bash
set -e
cmake --build dist/linux

run-bin.sh

#!/usr/bin/env bash
set -e
./dist/linux/app

Grant execute permissions on Ubuntu before running: Предоставьте права на выполнение в Ubuntu перед запуском:

chmod +x config-bin.sh build-bin.sh run-bin.sh
./config-bin.sh
./build-bin.sh
./run-bin.sh

Step 4: Expected Output Шаг 4: Ожидаемый результат

After running the build and execution scripts, you should see output similar to this: После запуска скриптов сборки и выполнения вы должны увидеть результат, похожий на следующий:

Initializing Box2D v3 physics world...
Step 1 -> Position: (0, 3.99728) Angle: 0
Step 2 -> Position: (0, 3.98911) Angle: 0
Step 3 -> Position: (0, 3.9755) Angle: 0
Step 4 -> Position: (0, 3.95644) Angle: 0
Step 5 -> Position: (0, 3.93194) Angle: 0
Step 6 -> Position: (0, 3.902) Angle: 0
Step 7 -> Position: (0, 3.86661) Angle: 0
Step 8 -> Position: (0, 3.82578) Angle: 0
Step 9 -> Position: (0, 3.7795) Angle: 0
Step 10 -> Position: (0, 3.72778) Angle: 0
Box2D simulation finished successfully!