SFML 轴独立碰撞答案

【问题标题】：SFML Axis independent collisionSFML 轴独立碰撞
【发布时间】：2015-01-07 22:01:06
【问题描述】：

我已经在我的游戏中实现了 tilemap 碰撞，它可以工作，但是当我在一个轴上碰撞并试图在另一个轴上移动时，问题就出现了。我不能在墙上滑。

在 Player.cpp 中

void Player::update(float delta, std::vector<Tile>& tiles) {
    if (sf::Keyboard::isKeyPressed(sf::Keyboard::W) || sf::Keyboard::isKeyPressed(sf::Keyboard::Up) || sf::Joystick::getAxisPosition(0, sf::Joystick::Y) < -20) {
        newPos.y -= speed * delta;
    }
    if (sf::Keyboard::isKeyPressed(sf::Keyboard::A) || sf::Keyboard::isKeyPressed(sf::Keyboard::Left) || sf::Joystick::getAxisPosition(0, sf::Joystick::X) < -20) {
        newPos.x -= speed * delta;
    }
    if (sf::Keyboard::isKeyPressed(sf::Keyboard::S) || sf::Keyboard::isKeyPressed(sf::Keyboard::Down) || sf::Joystick::getAxisPosition(0, sf::Joystick::Y) > 20) {
        newPos.y += speed * delta;
    }
    if (sf::Keyboard::isKeyPressed(sf::Keyboard::D) || sf::Keyboard::isKeyPressed(sf::Keyboard::Right) || sf::Joystick::getAxisPosition(0, sf::Joystick::X) > 20) {
        newPos.x += speed * delta;
    }

    sf::Vector2f oldPos = sprite.getPosition();
    move(delta, newPos);

    for (int i = 0; i < tiles.size(); i++) {
        if (Collision::PixelPerfectTest(sprite, tiles[i].sprite) && tiles[i].collision) {
            sprite.setPosition(oldPos);
            newPos = oldPos;
        }
    }
}

void Player::move(float delta, sf::Vector2f position) {
    sprite.setPosition(position);
}

在 Collision.cpp 中

bool PixelPerfectTest(const sf::Sprite& Object1, const sf::Sprite& Object2, sf::Uint8 AlphaLimit) {
        sf::FloatRect Intersection;
        if (Object1.getGlobalBounds().intersects(Object2.getGlobalBounds(), Intersection)) {
            sf::IntRect O1SubRect = Object1.getTextureRect();
            sf::IntRect O2SubRect = Object2.getTextureRect();

            sf::Uint8* mask1 = Bitmasks.GetMask(Object1.getTexture());
            sf::Uint8* mask2 = Bitmasks.GetMask(Object2.getTexture());

            // Loop through our pixels
            for (int i = Intersection.left; i < Intersection.left + Intersection.width; i++) {
                for (int j = Intersection.top; j < Intersection.top + Intersection.height; j++) {

                    sf::Vector2f o1v = Object1.getInverseTransform().transformPoint(i, j);
                    sf::Vector2f o2v = Object2.getInverseTransform().transformPoint(i, j);

                    // Make sure pixels fall within the sprite's subrect
                    if (o1v.x > 0 && o1v.y > 0 && o2v.x > 0 && o2v.y > 0 &&
                        o1v.x < O1SubRect.width && o1v.y < O1SubRect.height &&
                        o2v.x < O2SubRect.width && o2v.y < O2SubRect.height) {

                        if (Bitmasks.GetPixel(mask1, Object1.getTexture(), (int)(o1v.x) + O1SubRect.left, (int)(o1v.y) + O1SubRect.top) > AlphaLimit &&
                            Bitmasks.GetPixel(mask2, Object2.getTexture(), (int)(o2v.x) + O2SubRect.left, (int)(o2v.y) + O2SubRect.top) > AlphaLimit)
                            return true;

                    }
                }
            }
        }
        return false;
    }

【问题讨论】：

标签： c++ collision sfml

【解决方案1】：

那是因为您的碰撞测试是全有或全无。我会做额外的碰撞测试，看看 x 或 y 新位置是否有效，例如：

if (tiles[i].collision && Collision::PixelPerfectTest(sprite, tiles[i].sprite))
{
    sf::Vector2f checkPosX = newPos;
    sf::Vector2f checkPosY = newPos;

    checkPosX.y = oldPos.y;
    checkPosY.x = oldPos.x;

    sprite.setPosition(checkPosX);

    if (!Collision::PixelPerfectTest(sprite, tiles[i].sprite))
    {
        newPos = checkPosX;
    }
    else
    {
        sprite.setPosition(checkPosY);

        if (!Collision::PixelPerfectTest(sprite, tiles[i].sprite))
        {
            newPos = checkPosY;
        }
        else
        {
            sprite.setPosition(oldPos);
            newPos = oldPos;
        }
    }
}

顺便说一句，如果您首先测试tiles[i].collision，由于表达式短路，您将跳过更昂贵的非碰撞瓷砖PixelPerfectTest() 测试。

【讨论】：