Question

Problem: move an object along a straight line at a constant speed in the Cartesian coordinate system (x,y only). The rate of update is unstable. The movement speed must be close to exact and the object must arrive very close to the destination. The line’s source and destination may be anywhere.

Given: the source and destination addresses (x0,x1,y0, y1), and a speed of arbitrary value.

An asside: There is an answer on the SO regarding this, and it’s good, however it presumes that total time spend traveling is given.

Here’s what I’ve got:

x0 = 127;
y0 = 127;
x1 = 257;
y1 = 188;
speed = 127;
ostrich.x=x0 //plus some distance along the line;
ostrich.y=y0 // plus some distance along the line;
//An arbitrarily large value so that each iteration increments the distance a minute amount
SPEED_VAR = 1000; 
xDistPerIteration = (x1 - x0) / SPEED_VAR;
yDistPerIteration = (y1 - y0) / SPEED_VAR;
distanceToTravel = ;//Pythagorean theorum
limitX =  limit1 = 0; //determines when to stop the while loop

//get called 40-60 times per second
void update(){
  //Keep incrementing the ostrich' location
  while (limitX < speed && limitY < speed) {
    limitX += Math.abs(xDistPerIteration);
    limitY += Math.abs(yDistPerIteration);
    ostrich.x += xDistPerIteration;
    ostrich.y += yDistPerIteration;
  }
  distanceTraveled -= Math.sqrt(Math.pow(limitX, 2) + Math.pow(limitY, 2));
  if (distanceTraveled <=0)
    //ostrich arrived safely at the factory
}

This code gets the job done, however it takes up exclusively 18% of program time in a CPU intensive program. It's garbage, programatically and in terms of performance. Any ideas on what to do here?

Answer 1

An asside: There is an answer on the
SO regarding this, and it’s good,
however it presumes that total time
spend traveling is given.

basic physics to the rescue

total time spent traveling = distance/speed

btw Math.hypot(limitX,limitY) is faster than Math.sqrt(Math.pow(limitX, 2) + Math.pow(limitY, 2))

though really it’s that while loop you should refactor out