C ++矩形到矩形碰撞

Question

I'm having a really bad time here looking for the error in my code.

My collision detection won't work here even the algorithm I searched in Google.

void PollEvents()
{

for (int i = 0;i < NUMBER_OF_BLOCKS; ++i)
{

    Rectangle& a = blocks[i];

    if (mouse.state == GLFW_PRESS)
    {   
        //look for any block to grab
        if (mouse.leftClick && !blocks[selectedBlock].Grab() &&
            a.Hover(mouse.pos.x, mouse.pos.y))
        {
            //prevent grabbing another block
            if (i != selectedBlock) {
                selectedBlock = i;
            }

            a.Grab() = true;

            if (a.IsTypeHorizontal()) {
                diff = mouse.pos.x - a.Left();
            } else {
                diff = mouse.pos.y - a.Top();
            }
        }

        if (a.Grab())
        {   

            for (int j = 0;j < NUMBER_OF_BLOCKS; ++j)
            {
                //skip for any self-checking
                if (i == j) continue;

                Rectangle& b = blocks[j];

                //check for rectangle collision
                if (!a.Collide(b) || b.Collide(a)) {
                    //j++;
                    //how does this block will move.

                    if (a.IsTypeVertical()) {
                        a.SetY(mouse.pos.y - diff);
                    } else {
                        a.SetX(mouse.pos.x - diff);
                    }

                } else {

                    switch (a.sideHit)
                    {
                    case UP:
                        //a.SetY(b.Bottom());
                        printf("UP\n");
                        break;
                    case DOWN:
                        //a.SetY(b.Top() + a.GetHeight());
                        printf("DOWN\n");
                        break;
                    case LEFT:
                        //a.SetX(b.Right());
                        printf("LEFT\n");
                        break;
                    case RIGHT:
                        //a.SetX(b.Left() - a.GetWidth());
                        printf("RIGHT\n");
                        break;
                    }
                }

                //check for bound collision
                a.BoundCheck(1.f);
            }

        }

    } else {
        a.Grab() = false;
    }
}
}

---

Collision detection:

bool Rectangle::Collide(const Rectangle& r) {

if (IsTypeHorizontal()) {
    if (r.Hover(Left(), Top()) && r.Hover(Right(), Top())) {
        sideHit = UP;
        return true;
    } else if (r.Hover(Right(), Bottom()) && r.Hover(Left(), Bottom())) {
        sideHit = DOWN;
        return true;
    }
    // } else if (r.Hover(Left(), Top())) {
        // sideHit = UP;
        // return true;
    // } else if (r.Hover(Right(), Top())) {
        // sideHit = UP;
        // return true;
    // } else if (r.Hover(Right(), Bottom())) {
        // sideHit = DOWN;
        // return true;
    // } else if (r.Hover(Left(), Bottom())) {
        // sideHit = DOWN;
        // return true;
    // }
} else {
    if (r.Hover(Left(), Top()) && r.Hover(Left(), Bottom())) {
        sideHit = LEFT;
        return true;
    } else if (r.Hover(Right(), Top()) && r.Hover(Right(), Bottom())) {
        sideHit = RIGHT;
        return true;
    }
    // } else if (r.Hover(Left(), Top())) {
        // sideHit = LEFT;
        // return true;
    // } else if (r.Hover(Left(), Bottom())) {
        // sideHit = LEFT;
        // return true;
    // } else if (r.Hover(Right(), Top())) {
        // sideHit = RIGHT;
        // return true;
    // } else if (r.Hover(Right(), Bottom())) {
        // sideHit = RIGHT;
        // return true;
    // }
}

return false;

}

Code for Hover :

inline float Hover(float X, float Y) const {
    return  X >= Left() &&
            X <= Right() &&
            Y >= Bottom() &&
            Y <= Top();
}

I'm trying to make my own unblockme .

Please help me on my collision-detection. It's been 3 days now since I got stuck in this problem.

UPDATE

I have found out the problem why all rect-rect collision detection won't work in my program.

Bug:

if (!a.Collide(b)) {

    //Move()

} else {

    //Resolve collision
}

This one should be

if (!Rectangle::Collide(a, b)) {

    //Move()

} else {

    //Resolve collision

}

Making the Collide() a static member of Rectangle because, as you can see in my implementation of Collide() , it bases its decision on its own member so a.Hover(bx, by) doesn't make any sense.

Hope this helps a little bit to all newbies like me.

Answer 1

To do rect/rect collision detection, if any of one (edges parallel to x and y axis) rect's four points is inside the other rect, we have a collision.

An easier way than to check each of the four points is to check if one X edge is between both the other rect's X edges, and if one Y edge is between both the other rect's Y edges - if both are true, we have a collision (because the two edges must meet at a point inside of the other rect). So we just check this in both directions:

bool isclamped(float mid, float A, float B)
{
    if (A > B)
    {
        return mid >= B && mid <= A;
    }
    return mid >= A && mid <= B;
}

bool checkcollisiononeway(rect rectA, rect rectB)
{
    if (isclamped(rectA.left, rectB.left, rectB.right)
    || isclamped(rectA.right, rectB.left, rectB.right))
    && (isclamped(rectA.bottom, rectB.bottom, rectB.top)
    || isclamped(rectA.top, rectB.bottom, rectB.top))
    {
        return true;
    }
    return false;
}

bool checkcollisionbothways(rect rectA, rect rectB)
{
    return checkcollisiononeway(rectA, rectB) || checkcollisiononeway(rectB, rectA);
}

To determine the angle of collision after detecting a collision, find the angle between their two centers using atan2(rectA.y - rectB.y, rectA.x - rectB.x) (the angle is returned in radians, not in degrees)