Can't get the right angle...

no-reply@allegro.cc (armond) — Wed, 02 May 2007 16:54:35 +0000

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!

no-reply@allegro.cc (Ceagon Xylas) — Wed, 02 May 2007 17:38:31 +0000

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

no-reply@allegro.cc (armond) — Wed, 02 May 2007 18:55:42 +0000

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

no-reply@allegro.cc (Ceagon Xylas) — Wed, 02 May 2007 19:05:28 +0000

[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);
  }
}

1	if ( s->isVisible() )
2	{
3	//wc->fireWeapon();
4
5	std::cout << "targetY: " << targetY << " sY: " << sY << std::endl;
6	std::cout << "targetX: " << targetX << " sX: " << sX << std::endl;
7
8	int r1 = (targetY - sY);
9	int r2 = (targetX - sX);
10
11	if (r1 == 0)
12	{
13	r1 = 1;
14	}
15
16	if (r2 == 0)
17	{
18	r2 = 1;
19	}
20
21	fixed fangle = fatan( itofix(r1 / r2) );
22	int angle = fixtoi(fangle);
23
24	std::cout << "angle: " << angle << std::endl;
25
26	wc->getCurrentWeapon()->fire(angle);
27	}

1	void Vulcan::update()
2	{
3	fixed fAngle = ftofix( (angle) );
4
5	int newX = 0;
6	int newY = 0;
7
8	if (this->x < SCREEN_W)
9	{
10	newX = x + (speed * fixtoi( fcos(fAngle) ) );
11	newY = y + (speed * fixtoi( fsin(fAngle) ) );
12	move(newX, newY);
13
14	animation->animate();
15	}
16
17	}