DeltaTime

poisson86

Hey, I'm doing a game and I'd like to know if it's possible to have the delta time in Processing ? :)

GoToLoop

I'm afraid those delta nano time calculations are done internally via local variables: :(
https://GitHub.com/processing/processing/blob/master/core/src/processing/core/PApplet.java#L2379

Most we can access is the protected field frameRateLastNanos.
Which is nothing more than the previous System.nanoTime():
https://GitHub.com/processing/processing/blob/master/core/src/processing/core/PApplet.java#L2445

There's also field frameRate:
https://Processing.org/reference/frameRate.html

Dunno how useful that'll be for ya, but here's some test I did now: 8-|

long prev;

void setup() {
  frameRate(60);
  println(1e3/60); // 60 FPS = 1e3/60 = 16.666666
}

void draw() {
  double delta = (-prev + (prev = frameRateLastNanos))/1e6d;
  println(delta, TAB, frameRate);
}

poisson86

I'm checking it, deltaTime is used for not base a program on processor power

koogs

you can maybe use millis() or access the underlying java millisecond and "nanosecond" timers.

http://stackoverflow.com/questions/351565/system-currenttimemillis-vs-system-nanotime

if you set the framerate as high as possible then it'll effectively disable the 60fps 'ticks' that are the default.

poisson86

What are "1e3" and "1e6d" ??

koogs

1000 and 1000000

engineering notation for numbers, used to confuse people.

https://en.wikipedia.org/wiki/Engineering_notation

the d in 1e6d is to denote a double precision floating point number.

poisson86

Okay :) didn't know about this

jeremydouglass

A simple method is to just use millis(), which will give you the time from sketch start in milliseconds. This doesn't give you nanoseconds, but should be fine for many applications.

To compute a time difference, just save millis() to a variable on an event -- then compare that variable to the current millis(), e.g.:

int lastTime = 0;
int delta = 0;
void draw(){
  delta = millis() - lastTime;
  println(delta);
  // draw code here
  lastTime = millis();     
}

A simple example of a timed action is to test how long a key was held down:

void draw(){
  // draw code here
}
void keyPressed(){
  int time1 = millis();
}
void keyReleased(){
  int time2 = millis() - time1;
  println(time2)
}

poisson86

That's the same thing, millis or nanosecond ^^

koogs

you might need to use a long rather than an int for nanoTime(). and nanoseconds may be negative... see the javadoc for System.nanoTime()

https://docs.oracle.com/javase/7/docs/api/java/lang/System.html#nanoTime()

jeremydouglass

@poisson86 -- re:"That's the same thing" -- no, I don't believe that milliseconds and nanoseconds are the same thing -- from discussion I've seen I believe that System.nanoTime is different, e.g.

nanoTime is usually significantly more accurate than currentTimeMillis but it's a relatively expensive call as well.currentTimeMillis() runs in a few (5-6) cpu clocks, nanoTime depends on the underlying architecture and can be 100+ cpu clocks.