将轴对齐的矩形旋转90度

时间:2015-04-04 19:05:37

标签: c++ rotation 2d sfml

我有矩形对象(sf::IntRect),其属性:2D平面上的左,顶部,宽度和高度。我想在点(0,0)附近旋转90度(即90度,180度或270度)的倍数。因此我正在写一个这样的函数:

void rotateRect(sf::IntRect& rect, int rot)
{
    //code I need
}

旋转为0(0),1(90),2(180)或3(270)。

如何尽可能简单地实现这一目标。

1 个答案:

答案 0 :(得分:0)

以下是sf::Tranform上使用sf::FloatRect的基本解决方案:

constexpr auto rotationAngle(int rot) { return rot * 90.f; }

void rotateRect(sf::IntRect& rect, int rot)
{
    auto deg = rotationAngle(rot);
    auto transform = sf::Transform();
    transform.rotate(deg);

    // Would be better if rect was a FloatRect...
    auto rectf = sf::FloatRect(rect);
    rectf = transform.transformRect(rectf);
    rect = static_cast<sf::IntRect>(rectf);
}

但是,我个人会稍微改变你的函数的签名来使用float rects和更紧凑的表示法:

sf::FloatRect rotateRect(sf::FloatRect const& rect, int rot)
{
    return sf::Transform().rotate(rotationAngle(rot)).transformRect(rect);
}

下面是一个完整的例子,展示了它的行为方式。

#include <SFML/Graphics.hpp>

constexpr auto rotationAngle(int rot) { return rot * 90.f; }

sf::FloatRect rotateRect(sf::FloatRect const& rect, int rot)
{
    return sf::Transform().rotate(rotationAngle(rot)).transformRect(rect);
}

void updateShape(sf::RectangleShape& shape, sf::FloatRect const& rect)
{
    shape.setPosition(rect.left, rect.top);
    shape.setSize({ static_cast<float>(rect.width), static_cast<float>(rect.height) });
}

int main(int, char const**)
{
    sf::RenderWindow window(sf::VideoMode(500, 500), "rotate");

    auto rect = sf::FloatRect(0, 0, 100, 50);
    auto shape = sf::RectangleShape();
    shape.setFillColor(sf::Color::Red);
    updateShape(shape, rect);

    auto view = window.getView();
    view.move({ -250, -250 });
    window.setView(view);

    while (window.isOpen())
    {
        sf::Event event;
        while (window.pollEvent(event))
        {
            if (event.type == sf::Event::Closed)
                window.close();

            if (event.type == sf::Event::KeyReleased && event.key.code == sf::Keyboard::R)
            {
                rect = rotateRect(rect, 1);
                updateShape(shape, rect);
            }

            if (event.type == sf::Event::KeyReleased && event.key.code == sf::Keyboard::N)
            {
                rect = sf::FloatRect(50, 50, 100, 50);
                updateShape(shape, rect);
            }

            if (event.type == sf::Event::KeyReleased && event.key.code == sf::Keyboard::M)
            {
                rect = sf::FloatRect(0, 0, 100, 50);
                updateShape(shape, rect);
            }
        }

        window.clear();
        window.draw(shape);
        window.display();
    }

    return EXIT_SUCCESS;
}

注意:我使用了C ++ 14中的一些技巧,但我确定如果需要,可以将该代码转换为C ++ 11 / C ++ 98。