Thread: Incrementing along a vector

  1. #1
    Registered User
    Join Date
    Apr 2004

    Incrementing along a vector

    Hi again,

    Im making a program in c++ using openGL (glut) but having a little trouble figuring out how i would increment along a certain path...

    I have quite a few functions that require it like the one below, where i have the Point (contains x,y,z components) of the waypoint i need to head towards, and i have the angle to that waypoint from the current x,y,z position. Plus i can get the current position Point by just calling body->Get_Position(); if i need too.

    But im just not sure how i would set the incrementation Point's x,y,z to send to the Set_Position function.

    I would take a guess and say that if its walking and the angle rotates the view so its facing the waypoint, i would just increment the -z value of the current Point position by WALK_SPEED ? (WALK_SPEED is a #define)

    but im not sure. Could anyone please give me some advice?


    void AI::Patrol() {
    	Point increment;
            Point wp = Next_Waypoint();
    	float angle = Get_Position_Angle(wp);
            float range = Get_Range(wp);
    	//How to get the incrementation in step?
    	//increment.x = ?
    	//increment.y = ?
    	//increment.z = ?
    	//WALK_SPEED ?
    	//RUN_SPEED ?

    (i get the angle through this function, which i hope is correct)
    float AI::Get_Position_Angle(Point pos) {
          float angle;
    	  //Get the float angle between NPC position and parametre position
          angle = atan2(body->Get_Position().z-pos.z, body->Get_Position().x-pos.x)*(180 / PI);
          angle -= body->Get_Yaw();
          return angle;

  2. #2
    Registered User
    Join Date
    Apr 2004
    please could someone give me some advice on this? :P

  3. #3
    Registered User
    Join Date
    May 2003
    Okay, here's some code for how you handle things; note of course you'd need to define the operators +, -, and *, and the normalize function:

    Vector position; // This should be set with the current position
    Vector destination; // The x,y,z, coordinates of the destination

    Vector path = destination - position; // Subtract to get a vector representing the path we are walking
    double stepsize = 10.0; // How many units we should move in one step
    Vector step = path.normalize() * stepsize; // Here, normalize() returns a new vector that is the normalized (i.e. length 1) version of path.

    position = position + step; // Update the location
    Last edited by Cat; 11-01-2006 at 02:48 PM.
    You ever try a pink golf ball, Wally? Why, the wind shear on a pink ball alone can take the head clean off a 90 pound midget at 300 yards.

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