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C++ graphics programming: achieving real-time interactivity

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Release： 2024-06-02 12:42:57

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C++ There are two main techniques for achieving real-time interactivity in graphics programming: Event handling: using libraries (such as SFML) to detect and respond to user input, such as mouse movements, keyboard presses. Loops: Continuously execute a block of code, updating game state, drawing graphics, and processing input until certain conditions are met. Practical case: Snake game: Use SFML for event processing, and achieve real-time interactivity of the Snake game by looping to update the snake's body position, check collisions and draw graphics.

C++ graphics programming: achieving real-time interactivity

C++ Graphics Programming: Achieving Real-Time Interactivity

Introduction

Real-time Interaction Performance is a key aspect of graphics applications, allowing users to control and manipulate the objects displayed in the application. In C++, you can use a variety of techniques to achieve real-time interactivity, such as event handling and loops.

Event handling

Event handling is a technology that detects and responds to user input (such as mouse movements, keyboard presses). In C++, you can use libraries such as SFML (Simple and Intuitive Media Library) for event handling.

Code Example:

#include <SFML/Graphics.hpp>

int main()
{
    sf::RenderWindow window(sf::VideoMode(800, 600), "实时交互性");

    while (window.isOpen())
    {
        sf::Event event;
        while (window.pollEvent(event))
        {
            if (event.type == sf::Event::Closed)
                window.close();
            else if (event.type == sf::Event::MouseButtonPressed)
                std::cout << "鼠标按下了" << std::endl;
        }

        window.clear();
        // 绘制图形...
        window.display();
    }
}

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Loop

A loop is a block of code that continues to execute until a specific condition is met. In graphics applications, loops are used to update game state, draw graphics, and respond to input.

Code example:

#include <iostream>
#include <thread>

using namespace std;

int main()
{
    bool running = true;

    while (running)
    {
        // 游戏状态更新...
        // 绘制图形...

        // 处理输入
        char input;
        cin >> input;

        if (input == 'q')
            running = false;
    }
}

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Practical case

The following is an example of a real-time interactive C++ graphics application. Using SFML for event handling:

Snake game

Snake is a classic snake game in which players control a snake to eat food in a maze. Using C++ and SFML we can implement a simple version of the Snake game:

#include <SFML/Graphics.hpp>

const int GRID_SIZE = 20;

int main()
{
    sf::RenderWindow window(sf::VideoMode(800, 600), "贪吃蛇");

    // 初始化蛇的身体
    std::vector<sf::RectangleShape> snake;
    snake.emplace_back(sf::RectangleShape(sf::Vector2f(GRID_SIZE, GRID_SIZE)));
    snake[0].setPosition(GRID_SIZE, GRID_SIZE);

    // 初始化食物
    sf::RectangleShape food(sf::Vector2f(GRID_SIZE, GRID_SIZE));
    food.setPosition(rand() % (800 / GRID_SIZE) * GRID_SIZE, rand() % (600 / GRID_SIZE) * GRID_SIZE);

    sf::Clock clock;
    sf::Time timeSinceLastUpdate = sf::Time::Zero;
    sf::Time timePerFrame = sf::seconds(1 / 60.0f);

    bool running = true;
    sf::Vector2i direction = sf::Vector2i(0, 0);

    while (running)
    {
        sf::Event event;
        while (window.pollEvent(event))
        {
            if (event.type == sf::Event::Closed)
                running = false;
            else if (event.type == sf::Event::KeyPressed)
            {
                if (event.key.code == sf::Keyboard::Up)
                    direction = sf::Vector2i(0, -1);
                else if (event.key.code == sf::Keyboard::Down)
                    direction = sf::Vector2i(0, 1);
                else if (event.key.code == sf::Keyboard::Left)
                    direction = sf::Vector2i(-1, 0);
                else if (event.key.code == sf::Keyboard::Right)
                    direction = sf::Vector2i(1, 0);
            }
        }

        timeSinceLastUpdate += clock.restart();

        if (timeSinceLastUpdate >= timePerFrame)
        {
            // 更新游戏状态
            sf::Vector2i newPosition = snake.front().getPosition() + (direction * GRID_SIZE);

            // 检查边界碰撞
            if (newPosition.x < 0 || newPosition.x >= 800 || newPosition.y < 0 || newPosition.y >= 600)
                running = false;

            // 检查自身碰撞
            for (size_t i = 1; i < snake.size(); i++)
            {
                if (newPosition == snake[i].getPosition())
                    running = false;
            }

            // 检查食物碰撞
            if (newPosition == food.getPosition())
            {
                snake.emplace_back(sf::RectangleShape(sf::Vector2f(GRID_SIZE, GRID_SIZE)));
                snake.back().setPosition(newPosition);

                food.setPosition(rand() % (800 / GRID_SIZE) * GRID_SIZE, rand() % (600 / GRID_SIZE) * GRID_SIZE);
            }
            else
            {
                snake.emplace_back(sf::RectangleShape(sf::Vector2f(GRID_SIZE, GRID_SIZE)));
                snake.back().setPosition(newPosition);

                snake.erase(snake.begin());
            }

            // 绘制图形
            window.clear();

            for (auto& rect : snake)
                window.draw(rect);

            window.draw(food);

            window.display();

            timeSinceLastUpdate = sf::Time::Zero;
        }
    }
}

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