Can't get the right angle...

Can't get the right angle...

armond

Member #8,282

January 2007

Hi guys! I thought I could get away with my hacks. But when I needed to track a certain object's angle things started to get messy.

In a certain class, I have the following code...

  if ( s->isVisible() )
  {
      //wc->fireWeapon();
      
      std::cout << "targetY: " << targetY << " sY: " << sY << std::endl;
      std::cout << "targetX: " << targetX << " sX: " << sX << std::endl;
7 
      int r1 = (targetY - sY);
      int r2 = (targetX - sX);
      
      if (r1 == 0)
      {
          r1 = 1;
      }
      
      if (r2 == 0)
      {
          r2 = 1;
      }
20 
      fixed fangle = fatan( itofix(r1 / r2) );
      int angle = fixtoi(fangle);
      
      std::cout << "angle: " << angle << std::endl;
      
      wc->getCurrentWeapon()->fire(angle);
  }

When weapon is fired and releases a projectile... The projectile moves like this...

1void Vulcan::update()
2{            
  fixed fAngle = ftofix( (angle) );
  
  int newX = 0;
  int newY = 0;
      
  if (this->x < SCREEN_W)
  {
      newX = x + (speed * fixtoi( fcos(fAngle) ) );
      newY = y + (speed * fixtoi( fsin(fAngle) ) );
      move(newX, newY);
     
      animation->animate();
  }   
   
17}

I'm aware that my code(if it ever went well) would move in only 8 directions. But I could live with that. What I don't want is that my projectile doesn't go in the right direction like when I'm on the left side, the enemy would shoot right! Thanks for the help!

Ceagon Xylas

Member #5,495

February 2005

Do you have to use fixed point? I suggest radian.

armond

Member #8,282

January 2007

Thanks for the link. BTW, it seems like functions like fatan, fcos, and fsin requires a fixed type?

Ceagon Xylas

Member #5,495

February 2005

[long time later, I realized I was mistaken. So I rewrote this to just say...]
Use cosf, sinf, and tanf for float values.

This may be the source of the problem you're having. Try something like this

if(s->isVisible()){
  float angle=atan2f(targetY-sY,targetX-sX);
  wc->getCurrentWeapon()->fire(angle);
}

void Vulcan::update() {
  if(x < SCREEN_W) {
    float newX=x+speed*cosf(angle);
    float newY=y+speed*sinf(angle);
    move(newX,newY);
  }
}