Can't get the right angle...
armond

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...

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 }

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

1void 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}

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

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

armond

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

Ceagon Xylas

[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);
  }
}

Thread #591237. Printed from Allegro.cc