Circle collision detection and Vector math: HELP?
- by Griffin
Hey so i'm currently going through the wildbunny blog to learn about collision detection, but i'm a bit confused on how the vectors he's talking about come into play
QUOTED BLOG:
  p = ||A-B|| – (r1+r2) 
  
  The two spheres are penetrating by
  distance p. We would also like the
  penetration vector so that we can
  correct the penetration once we
  discover it. This is the vector that
  moves both circles to the point where
  they just touch, correcting the
  penetration. Importantly it is not
  only just a vector that does this, it
  is the only vector which corrects the
  penetration by moving the minimum
  amount. This is important because we
  only want to correct the error, not
  introduce more by moving too much when
  we correct, or too little.
  
  N = (A-B) / ||A-B||
  
  P = N*p
  
  Here we have calculated the normalised
  vector N between the two centres and
  the penetration vector P by
  multiplying our unit direction by the
  penetration distance.
Ok so i understand that p is the distance each circle is penetrating each other, but i don't get what exactly N and P is. it seems to me N is just the coordinates of the 3rd point of the right trianlge formed by point A and B (A-B) then being divided by the hypotenuse of that triangle or distance between A and B (||A-B||) Whats the significance of this?
Also, what is the penetration vector used for? It seems to me like a movement that one of the circles would perform to get un-penetrated.