Angle of Trajectory?

This is a discussion on Angle of Trajectory? within the Game Programming forums, part of the General Programming Boards category; I'm trying to create a bullet class that stores the bullets current position (x,y,z) and its trajectory. Traditionally I've used ...

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    napKINfolk.com napkin111's Avatar
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    Angle of Trajectory?

    I'm trying to create a bullet class that stores the bullets current position (x,y,z) and its trajectory. Traditionally I've used 3 variables called xtraject, ytraject, and ztraject where each loop xtraject was added to x and same for y/z. So in order to get the bullet travelling upper right at a 45 degree angle xtraject and ytraject would be 1. I'm want to have bullets that can fire at arbitrary angles, perhaps just have an angle variable (maybe I would need 2?) to control which way it goes and then a speed to say how fast its moving.

    Do I use polar coordinates to do this? What about quaternions?

    Thanks,

    //napKIN
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    Super Moderator VirtualAce's Avatar
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    Although that post is really not about the same thing. There is another post here about bullets that covers it better.

    Essentially:


    Code:
    #define PI 3.14159
    #define DEGTORAD(angle) ((double)angle*PI/180.0)
    
    struct point2D
    {
      double x;
      double y;
    };
    
    struct Bullet
    {
       point2D Pos;
       point2D Vel;
       double speed;
       int active;
    };
    
    void FireBullet(point2D Start,int angle,double speed,Bullet *newbullet)
    {
      newbullet->x=Start.x;
      newbullet->y=Start.y;
      newbullet->vel.x=cos(DEGTORAD(angle));
      newbullet->vel.y=sin(DEGTORAD(angle));
      newbullet->speed=speed;
      newbullet->active=TRUE;
    }
    
    //Assuming we have an array of Bullet objects called Bullets
    void UpdateBullets
    {
      for (int i=0;i<NumBullets;i++)
      {
         if (Bullets[i].active)
         {
            Bullets[i].x+=(Bullets[i].vel.x*Bullets[i].speed);
            Bullets[i].y+=(Bullets[i].vel.y*Bullets[i].speed);
         }
       }
    }
    This is only for 2D, for 3D you must do a little more.

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