CODEWITHSUNDEEP
c++collision
Eduardo Gomez
Eduardo Gomez

Reputation: 41

Block movement between rectangles c++ (collison done)

I have two rectangles, one of them stationary. Whenever I try to move one towards another I want it to 'slide' rather than getting stuck without being able to move. I use oriented bounding boxes and the code is fairly tested, but I don't know how to avoid them getting stuck.

Collision between two rectangles

Currently what I do is this:

o1 = o;

vector2df vxy = o.V;

o1.Pos += vxy;

if(o1.overlaps(o2)){

  o1 = o;
  o1 += vector2df(0.f, vxy.y);

  if(o1.overlaps(o2)){
    vxy.y = 0;
  }

  o1 = o;
  o1 += vector2df(vxy.x, 0.f);

  if(o1.overlaps(o2)){
    vxy.x = 0;
  }

}

o1.V = vxy

Which is quite 'dirty' as it just checks if the movement can be done in either X and Y, disabling it if it collides individually.

The velocity is a float, so later it will just add it.

I had thought doing a while loop until it doesn't collide, leaving the smaller value in which it won't collide, but it either doesn't work or is stuck in an infinite loop...

Upvotes: 1

Views: 175

Answers (1)

Eliott Gaboreau
Eliott Gaboreau

Reputation: 186

I'm guessing the first thing to do would be to rewind your moving box's movement so that it doesn't collide anymore with your fixed box. Right now your boxes are probably staying in a colliding state, hence the infinite loop.

Then as for determining the new velocity of your moving box, you probably want to get the direction of the edge from your fixed box your moving box is colliding with and set that as your new velocity.

You also might want at some point to multiply this new velocity by the dot product of your initial velocity and your new direction, so that when the moving box goes perpendicular to the fixed box's edge, it basically stops, but if it's going at a sharp angle it doesn't loose much speed.

All of this describes a vastly oversimplified approach, you might want to read more about basic game engines/physics/collision detection if you want a cleaner result.

Hope this helps.

Upvotes: 2

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