Java libgdx：限制圆周速度（摆动实体）答案

【问题标题】：Java libgdx: limiting circular velocity (swinging entity)Java libgdx：限制圆周速度（摆动实体）
【发布时间】：2016-09-02 00:33:36
【问题描述】：

我目前正在开发一个 2D 横向卷轴，并且已经实现了 this 文章中用于抓钩的技术，并且效果非常好。我的问题是我希望我的玩家能够围绕绳索摆动一点以获得一点动力，但目前我无法阻止玩家一直移动到任一侧 90 度。可以应用哪些技术来强制执行此限制？

我曾尝试使用单独的球员速度进行挥杆，但这只会减慢速度，我仍然可以每边最多挥杆 90 度。

这是我在播放器中的更新功能

public void update(float dt){
    //handle friction and air resistance
    if(dx !=0){
        if(touchingGround) {
            // apply friction
            if (dx > 0) {
                dx -= retardation;
            } else {
                dx += retardation;
            }
        } else {
            //applied air resistance
            if (dx > 0) {
                dx -= airResistance;
            } else {
                dx += airResistance;
            }
        }
    }
    // handle gravity
    dy -= Constants.GRAVITY * dt;
    if(dy < -terminalVelocity){
        dy = -terminalVelocity;
    }

    /*
        Handle Player movement
     */

    if(right){
        if(dx <= maxSpeed){
            dx += acceleration;
        }
        dx = maxSpeed;
    }

    if(left){
        if(dx <= -maxSpeed){
            dx -= acceleration;
        }
        dx = -maxSpeed;
    }

    if(isGrappling){

        //If we collide with something we need to stop grappling
        if(hasCollided){
            isGrappling = false;
        } else {

            //  This algorithm from here:
            // http://gamedev.stackexchange.com/questions/61596/player-rope-swing

            float currentD = (float) Math.sqrt(((grappleX - x) * (grappleX - x)) + ((grappleY - y) * (grappleY - y)));
            float prevX = getX(), prevY = getY();

            if (currentD > grappleRadius) {
                Vector2 hookPos = new Vector2(grappleX, grappleY);
                Vector2 testPos = (new Vector2(x, y).sub(hookPos)).nor();

                y = (hookPos.y + testPos.y * grappleRadius);
                x = (hookPos.x + testPos.x * grappleRadius);

                // s = d / t
                dx += (x - prevX) / dt;
                dy += (y - prevY) / dt;
            }
        }
    }

    /*
        Collision Detection, handle last always!
     */

    float oldX = getX(), oldY = getY();
    boolean collisionX = false, collisionY = false;

    // move on x
    x += dx * dt;

    // calculate the increment for step in #collidesLeft() and #collidesRight()
    increment = collisionLayer.getTileWidth();
    increment = getWidth() < increment ? getWidth() / 2 : increment / 2;

    if(dx < 0) // going left
        collisionX = collidesLeft();
    else if(dx > 0) // going right
        collisionX = collidesRight();

    // react to x collision
    if(collisionX) {
        setX(oldX);
        dx = 0;
    }

    // move on y
    y += dy * dt;

    // calculate the increment for step in #collidesBottom() and #collidesTop()
    increment = collisionLayer.getTileHeight();
    increment = getHeight() < increment ? getHeight() / 2 : increment / 2;

    if(dy < 0) {
        touchingGround = collisionY = collidesBottom();
        // we can only jump 2 times before we have to touch the floor again
        if(collisionY){
            numberOfJumps = 2;
        }
    } else if(dy > 0) {
        collisionY = collidesTop();
    }

    // react to y collision
    if(collisionY) {
        setY(oldY);
        dy = 0;
    }

    hasCollided = collisionX || collisionY;
}

【问题讨论】：

标签： java libgdx game-physics

【解决方案1】：

由于我没有使用任何物理引擎，因此我选择通过限制玩家可以对挥杆施加力的角度来模拟物理。

            // check if angle permits movement
            if(grappleAngle < Math.PI/9 && grappleAngle > -Math.PI/9) {
                // handle momentum gaining on rope
                if (right) {
                    dx += swingAcceleration * dt;
                }

                if (left) {
                    dx -= swingAcceleration * dt;
                }
            }

【讨论】：