I found this page today:

http://processing.org/hacks/hacks:collision_detection

Seeing as I work in games development, I know a more efficient method of testing circle collision than detailed on the page. But I can't edit the page for some reason.

I mean to change:
Code:

void circle_collision(x_1, y_1, radius_1, x_2, y_2, radius_2)
{
  return dist(x_1, y_1, x_2, y_2) < radius_1+radius_2;
}
 

to

Code:

void circle_collision(x_1, y_1, radius_1, x_2, y_2, radius_2)
{
  return (x_2 - x_1) * (x_2 - x_1) + (y_2 - y_1) * (x_2 - x_1) < (radius_1 + radius_2) * (radius_1 + radius_2);
}
 

Function calls are expensive. The squareroot required to measure distance is also expensive. By inlining the whole operation and avoiding using a squareroot, you get the most efficient circle collision test.

I'd put this on the hack page, but I can't figure out how.

hi aaron!

the page was acc. locked, fixed now. thanks for letting us know.

you can edit the content by clicking the edit button to the upper right of each block.

btw. i think your website has been hacked .. it redirects me to some virus scanner page ..

F

Code:

int timer, i;
void setup(){
  timer = millis();
  for(i = 0; i < 10000000; i++){
    circle_collision(1.0,2.0,3.0,4.0,5.0,6.0);
  }
  println(millis()-timer);
  timer = millis();
  for(i = 0; i < 10000000; i++){
    circle_collision2(1.0,2.0,3.0,4.0,5.0,6.0);
  }
  println(millis()-timer);
}
 Boolean circle_collision(float x_1, float y_1, float radius_1, float x_2, float y_2, float radius_2)
{
  return dist(x_1, y_1, x_2, y_2) < radius_1+radius_2;
}
 Boolean circle_collision2(float x_1, float y_1, float radius_1, float x_2, float y_2, float radius_2)
{
  return (x_2 - x_1) * (x_2 - x_1) + (y_2 - y_1) * (x_2 - x_1) < (radius_1 + radius_2) * (radius_1 + radius_2);
}
 

Runs twice as fast.

Also the methods on the page are listed as void, returning no value despite having return values, and there were no datatype idents.

there is a typo in the return statement, should be:
Code:

 Boolean circle_collision2(float x_1, float y_1, float radius_1, float x_2, float y_2, float radius_2)
{
  return (x_2 - x_1) * (x_2 - x_1) + (y_2 - y_1) * (y_2 - y_1) < (radius_1 + radius_2) * (radius_1 + radius_2);
}
 

//  fB