Collision Avoidance Example or Help

Question

I'm trying to find an example of collision avoidance that I can adapt and use for the game I'm working on. It will be used to simulate the movement of a skier to avoid trees on a hill. I base the Offing Behaviors movement on autonomous characters, and there are many good examples to follow and run off the road, but I cannot find good ones to prevent collisions. The Nature of Code website had awesome steering guides, but seemed to cover everything except preventing obstacles.

I converted the code from here , but it doesn’t work as good as it should, because collisions are detected by projecting the center of the obstacles onto the velocity vector without considering when the center of the obstacles can be outside the collision, but the circle is still colliding. Here is the code I adapted (written in the Processing section (based on Java)).

// Method to update location
void update() {
  // Update velocity
  vel.add(acc);
  // Limit speed
  vel.limit(maxspeed);
  loc.add(vel);
  // Reset accelertion to 0 each cycle
  acc.mult(0);
}

void obstacleAvoid() {
  float checkLength = 30*vel.mag();
  PVector forward,diff,ray,projection,force;
  float dotProd,dis;
  forward = vel.get();
  forward.normalize();
  ray = forward.get();
  ray.mult(checkLength);
  for ( int i = 0; i < obs.size(); i++ ) {
    Obstacle ob = (Obstacle)obs.get(i);
    diff = ob.pos.get();
    diff.sub(loc);
    PVector temp2 = forward.get();
    temp2.mult(ob.r);
    diff.sub(temp2);
    dotProd = diff.dot(forward);
    if ( dotProd > 0 ) {
      projection = forward.get();
      projection.mult(dotProd);
      dis = PVector.dist(projection,diff);
      if ( (dis < (ob.r + r)) && (projection.mag() < ray.mag()) ) {
        ob.hit = true;
        force = forward.get();
        force.mult(maxforce);
        if ( sign(diff,vel) == -1 ) { //CCW
          force.set(force.y,-force.x,0);
        }
        else { //CW
          force.set(-force.y,force.x,0);
        }
        force.mult(1-(projection.mag())/ray.mag());
        force.limit(maxforce);
        acc.add(force);
      }
    }
  }  
}

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Answer 1

Craig Reynolds . ++ OpenSteer, . . english . Java. , , Shiffman , , ,

Boids, . , . , PVector panic(ArrayList infected). , , . - :

void flock(ArrayList uninfected, ArrayList infected) {
  PVector sep = separate(uninfected);   // Separation
  PVector ali = align(uninfected);      // Alignment
  PVector coh = cohesion(uninfected);   // Cohesion
  PVector pan = panic(infected);        // Panic
  // Arbitrarily weight these forces
  sep.mult(4.0);
  ali.mult(1.0);
  coh.mult(2.0);
  pan.mult(-3.0);
  // Add the force vectors to acceleration
  acc.add(sep);
  acc.add(ali);
  acc.add(coh);
  acc.add(pan);
}

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Answer 2

NEHE:

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http://nehe.gamedev.net/data/lessons/lesson.asp?lesson=30

++ win32 API. Java Port JOGL.

http://www.red3d.com/cwr/steer/ http://opensteer.sourceforge.net/, ++. ?