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mathmotion

maths: motion depending on time

i have a mathematical problem:

i have a function where the only parameter is the current time. the return should be a position which is used to place an object on a certain place.

int position(int time)
{
    int x = 0; //TODO implement x depending on time
    return x;
}

so basically the function is called every frame to put the object in motion.

the motion should look like this (this is the actual question):

  1. a linear motion for time A, the object moves at constant speed
  2. no motion for time B, the object is stopped
  3. repeat at 1.

thanks!

edit: ok in other words: imagine a car that drives at constant speed for A minutes and then stops for B minutes. then drives again for A minutes and stops again for B minutes.

where is the car at time X?

Solution

  • OK, if I understand correctly:

    int position(int time)
{
    int count_of_AB_cycles = time / (A + B);
    int time_in_current_cycle = time % (A + B);
    int time_moved_this_cycle = (time_in_current_cycle < A) ? time_in_current_cycle : A;
    int total_time_moving = (count_of_AB_cycles * A) + time_moved_this_cycle;
    return total_time_moving * speed;
}

    assuming integer division, etc - you'll need floor()s if A and B are non-integers etc.