Game Development

AttackingHobo

22:00

I reached a playability point in my new game dl.dropboxusercontent.com/u/132671/RadStackingUnity/webbin.html

hasherr

@IcyDefiance This is what my movement was liek before I started making it be more affected by delta.

Jimmy

perhaps your deltas are too big then

radical

i would look at the time delta values for the frames and see if they are too small, making the position changes too small.

hasherr

delta is 128

John McDonald

So... you're doing:
velocity.x (or y) += accelerationConstant * deltaTime; // where deltaTime is in fractional seconds
then:
position += velocity;

Right?

Jimmy

22:01

perhaps it should be .128

like, try using seconds

instead of milliseconds

Icy Defiance

if delta is 128, that implies 8 fps

hasherr

* 1000, got it

Jimmy

because obviously velocity += acceleration * 128 is going to be huge if your units aren't properly adjusted

Lasse

@IcyDefiance this

Icy Defiance

also to get .128 from 128, you divide by 1k

hasherr

22:02

/ 1000 got it

John McDonald

deltaTime in seconds can be easier to work with because then all units like my accelerationConstant are in units / second

Icy Defiance

that's true as well

John McDonald

easier to think (even if the numbers are tiny)

Icy Defiance

right? thinking is already too hard. don't need to make it worse.

Jimmy

units per millisecond means your acceleration constants have to be scaled a million times smaller than you'd expect

hasherr

22:04

It still feels blocky :(

Icy Defiance

@Jimmy actually, only a thousand times smaller

to be technical

Jimmy

acceleration is 1/t^2

Lasse

@hasherr what is your calculated FPS?

Jimmy

velocity would be a thousand times

hasherr

hovering around 62

which still doens't make sense

because i'm synced at 60

Lasse

22:04

It can vary a bit from the 60

It's not perfect

hasherr

No, it wasn't like that before

Before I started messing with the timing, it never went higher than 60

Lasse

But if you have 62 fps then why do you have delta of 128

Icy Defiance

well you'd think it would vary equally in both directions from 60, but yes, the delta is the stranger part

hasherr

God dammit.

Lasse

your delta should be ~16 for 62 fps

John McDonald

22:06

If your deltaTime is in seconds, and you are getting ~60fps, your deltaTime should be about: 0.016666667

hasherr

What the helll are we we doing wrong?

Jimmy

not thinking about the value of deltaTime

radical

how about, just print the Sys.getTime(), and try manually computing the delta that you get, for few frames (not just 1) ?

and see if that matches what you are seeing as your computed delta time

hasherr

what the actual fuck

Delta: 128.0
X: 735.5163865074893 Y: 135.61602228484028
Delta: 0.0

Lasse

How did you get that output?

hasherr

22:08

We never fixed it, it just went from .128 to 128

@Lasse printing during movement

Lasse

did you replace all the floats to double?

John McDonald

Are you re-calculating the delta on each use?

hasherr

if (dir == Direction.NORTH)
        {
            velocity.y += 60f * Game.delta / 1000;
            debugPos();
        }
        if (dir == Direction.SOUTH)
        {
            velocity.y += -60f * Game.delta / 1000;
            debugPos();
        }
        if (dir == Direction.EAST)
        {
            velocity.x += 60f* Game.delta / 1000;
            debugPos();
        }
        if (dir == Direction.WEST)
        {
            velocity.x += -60f* Game.delta / 1000;
            debugPos();

Jimmy

I don't see where the delta comes from

John McDonald

I want to see the Game.delta definition

hasherr

22:10

time = getTime();
delta = time - lastFrame;
lastFrame = time;

John McDonald

The full definition

hasherr

getting repository ready, hold on

Icy Defiance

delta is a double, if he changed the right things earlier

Jimmy

Delta: 128.0
Time: 1.215529984E9
lastFrame: 1215529984

hasherr

github.com/hasherr/DinoPizzaAttack/blob/master/src/com/hasherr/…

Jimmy

22:11

can you actually just print the previous value of lastFrame instead of after you've already overwritten it

John McDonald

~~Pretty sure you are re-calculating the delta each time you use it, and that's wrong~~ I stand corrected

Lasse

return (Sys.getTime() * 1000.0f) / Sys.getTimerResolution();

take the f away

that defines it as a float, not sure what it does to the double values

hasherr

@Lasse You just did somehting big

Icy Defiance

@Lasse there are no double values at that point

hasherr

Delta: 17.0
X: 641.4981942348702 Y: 439.02538064695466
Delta: 17.0
X: 645.0030185058832 Y: 431.605730998175
Delta: 19.0
X: 647.3441945567388 Y: 424.2602777751238
Delta: 14.0

Icy Defiance

22:12

that's why I said 1000.0, not 1000.0f, though I should've emphasized that more

Jimmy

hey, that looks like 60 FPS >__>

hasherr

I should've paid more attention faceplam

Icy Defiance

@hasherr lesson here: calculations are done one operator at a time. the first calculation was an integer * float, which means the best resolution you would get from the division or anything after that was a float's resolution

which rendered all your double typing useless

hasherr

yes

Steady FPS: 60

Lasse

and the f was my mistake, but we were working with floats there anyway

Jimmy

22:14

another lesson might be that you could do deltas in ticks and avoid this issue

hasherr

Alright guys, thanks for all the help.

Icy Defiance

eh, maybe, but I'd do it in seconds instead

hasherr

I'M LEAVING IT

Icy Defiance

right now it's in milliseconds

you could make one more simple change though and make everything much easier in the future

Lasse

if you take the 1000 away (and cast it to double) then you get the delta in seconds

hasherr

22:15

@Override
    public void move(Direction dir)
    {
        if (dir == Direction.NORTH)
        {
            velocity.y += 60f * Game.delta / 1000;
            debugPos();
        }
        if (dir == Direction.SOUTH)
        {
            velocity.y += -60f * Game.delta / 1000;
            debugPos();
        }
        if (dir == Direction.EAST)
        {
            velocity.x += 60f* Game.delta / 1000;
            debugPos();
        }
        if (dir == Direction.WEST)
        {
            velocity.x += -60f* Game.delta / 1000;

John McDonald

@IcyDefiance ++

hasherr

Is there anything wrong with this?

Icy Defiance

just change "(Sys.getTime() * 1000.0f) / Sys.getTimerResolution()" to "(double)Sys.getTime() / Sys.getTimerResolution()"

Lasse

@hasherr if it works as intended, then no

Icy Defiance

so simple, and actually might save a small amount of processor power too

hasherr

22:16

It works great.

Icy Defiance

real small amount, but still

Lasse

yeah. do what icy said and remove all the /1000 and you are all set

hasherr

Alright, guys. Going for a victory run and then gonna make some food and read up on primitives.

Icy Defiance

aye

noooo, change thiiiiiings

Lasse

change is good!

Icy Defiance

22:17

oooooohhhhhhmmmm. change is goooooooood...

hasherr

Yeah, but it ain't easy.

Icy Defiance

pfft, this change is

hasherr

I woke up in a new buggatti

@Override
    public void move(Direction dir)
    {
        if (dir == Direction.NORTH)
        {
            velocity.y += 0.07 * Game.delta;
            debugPos();
        }
        if (dir == Direction.SOUTH)
        {
            velocity.y += -0.07f * Game.delta;
            debugPos();
        }
        if (dir == Direction.EAST)
        {
            velocity.x += 0.07f* Game.delta;
            debugPos();
        }
        if (dir == Direction.WEST)
        {
            velocity.x += -0.07f* Game.delta;

@IcyDefiance Is this better?

Icy Defiance

that's part 1

Lasse

why did you change the 60 to 0.07?

Icy Defiance

22:18

now do the other part

hasherr

What other part

Icy Defiance

3 mins ago, by Icy Defiance

just change "(Sys.getTime() * 1000.0f) / Sys.getTimerResolution()" to "(double)Sys.getTime() / Sys.getTimerResolution()"

then your delta will be in seconds instead of ms

which makes a lot of calculations easier to think through

hasherr

Oh, okay.

Yeah, that broke a bunch of shit.

John McDonald

Then you can think: "I'm accelerating at 0.07 units per second"

hmm

and 0.07 units per second is pretty slow, make that more like 20 or 100

Lasse

how did they break?

Jimmy

22:21

but he's actually accelerating at 70 units per second

Lasse

@Jimmy not anymore

hasherr

@Lasse It broke delta

Icy Defiance

@Jimmy velocity.x += 0.07f* Game.delta;

hasherr

Made delta 0 again.

Jimmy

yes, but that's with game.delta in ms

Icy Defiance

22:22

no you're crazy! craaazy!

John McDonald

0 or 0.0?

Icy Defiance

what's the exact line?

Jimmy

when you make it in terms of seconds, you also have to change it to 70 * dt

Lasse

try (double)Sys.getTime() / (double)Sys.getTimerResolution()

Jimmy

otherwise things just start moving really slowly

Lasse

22:22

it's not in ms anymore

Icy Defiance

@Lasse shouldn't be any different, unless java's really crazy

Lasse

java is really crazy

Icy Defiance

@Jimmy you're right, but if delta is really 0, that's not the first problem

hasherr

0.0

Jimmy

it's not 0, he' sjust printing it out to one digit

obviously it's going to read as 0.0

Icy Defiance

22:24

wrong again, that's just what the print does when it's converted to a string

hasherr

cries

Icy Defiance

hasherr! what exactly did you change that line to?!

John McDonald

There has to be int -> float issues somewhere

radical

nod

Icy Defiance

@JohnMcDonald double, not float. that was the original problem. we solved that.

I think he did the cast wrong

which is why I want to see the freaking line

John McDonald

22:25

well, double stands for "double precision floating point"

Icy Defiance

right. float was overflowing, though

hasherr

@IcyDefiance Exactly what you told me to change it to.

Icy Defiance

wrong answer

I want the line!

Lasse

paste the line

AttackingHobo

I wonder how many programming man years have been wasted on @hasherr

John McDonald

22:27

heh, oh fun. Sys.getTimerResolution() returns a long

Icy Defiance

show me the line! or the car fax. or something.

hasherr

@AttackingHobo Don't say wasted. lol

Jimmy

132123 years, if you count the months we were trying to explain matrix math back in the day

Lasse

@AttackingHobo wasted is such a strong word

Jimmy

oh god, the horrors

hasherr

22:27

(double)Sys.getTime() / Sys.getTimerResolution()

Icy Defiance

full line

John McDonald

I'm betting: return (Sys.getTime() * 1000.0f) / Sys.getTimerResolution(); also returns a float, divided by a long (converting to long), then returning a float

AttackingHobo

When people ask him something and he argues about it,and does shit like not posting the full line, that is wasting

Lasse

try adding the another (double) before the resolution

Icy Defiance

@JohnMcDonald yes, that was the original problem, so we changed the 1000.0f to 1000.0, and it fixed it

John McDonald

22:28

Double everything!

Icy Defiance

we're beyond that now

hasherr

public static double getTime()
    {
        return (double) (Sys.getTime() / Sys.getTimerResolution());
    }

Jimmy

lol

there you go

Lasse

adddddd theeee doubleeeee

Icy Defiance

THAT'S why I wanted the whole line

John McDonald

22:28

@IcyDefiance Are you really beyond that? You can get decimal places out of getTime()?

Jimmy

can you just copy exactly what people tell you to put there

Lasse

lol

Icy Defiance

(double) (Sys.getTime() / Sys.getTimerResolution()); is wrong

(double)Sys.getTime() / Sys.getTimerResolution(); is right

they're completely different

Lasse

maybe even (double)Sys.getTime() / (double)Sys.getTimerResolution() just to make sure

Icy Defiance

@JohnMcDonald oh yeah, we had it working until we made another change

Jimmy

22:29

@JohnMcDonald getTime is long

hasherr

X: 0.4400578482586007 Y: 0.9469621521198802
Delta: 0.01699999999254942

John McDonald

:D

Jimmy

so as long as you dvide by resolution ti should work

hasherr

Not sure what you're trying to accomplish.

That just broke it, as shown by the log.

Icy Defiance

@hasherr now, can you figure out why the two lines are different?

Jimmy

22:29

@hasherr that's the correct number now

Icy Defiance

that log looks correct to me

Lasse

@hasherr that's now correct

Jimmy

now just change your 0.07 to 70

John McDonald

@hasherr How is that broken?

Jimmy

because now you don't have to re-divide by 1000 again

John McDonald

22:30

24 mins ago, by John McDonald

If your deltaTime is in seconds, and you are getting ~60fps, your deltaTime should be about: 0.016666667

hasherr

oh!

X: 304.93129681107797 Y: 348.3419044163496
Delta: 0.01699999999254942

Works like a charm.

John McDonald

Yay!

hasherr

 public void move(Direction dir)
    {
        if (dir == Direction.NORTH)
        {
            velocity.y += 60 * Game.delta;
            debugPos();
        }
        if (dir == Direction.SOUTH)
        {
            velocity.y += -60f * Game.delta;
            debugPos();
        }
        if (dir == Direction.EAST)
        {
            velocity.x += 60f * Game.delta;
            debugPos();
        }
        if (dir == Direction.WEST)
        {
            velocity.x += -60f * Game.delta;

ARE YOU FUCKING HAPPY NOW

Lasse

@hasherr and do you see what we just did there? why we took the /1000 and *1000 away?

Icy Defiance

now! here's your quiz. what is the difference between these two lines?
(double) (Sys.getTime() / Sys.getTimerResolution());
(double)Sys.getTime() / Sys.getTimerResolution();

hasherr

22:31

@Lasse Yeah, I see it. TJis is definitely much more convinient and readable.

AttackingHobo

THE MAGIC OF ALGERBRA

Icy Defiance

@hasherr you're not allowed to write any more code until you can answer my quiz

2

AttackingHobo

^

Jimmy

^^

hasherr

@IcyDefiance A casts the whole thing as a double, B casts it so that just Sys.getTime() a double.

Icy Defiance

22:32

yes, but there's even more than that

hasherr

...

Icy Defiance

A) first does int / int, with an int answer. right there, you've lost all your decimal places.

Ali.S

I'm acutally tempted to buy super meat boy

Lasse

Sys.getTime() / Sys.getTimerResolution() = result is integer

Icy Defiance

then it casts the int answer to a double

Ali.S

22:33

for only 3$

Icy Defiance

which means your answer will be an int with .0 tacked on the end

hasherr

Ohh

Okay, I see

AttackingHobo

@Ali.S pretty good game but it has a dynamic timestep which is glitchy for fast moving games

hasherr

What do Sys.getTime() and Sys.getTimerRes return?

I don't know what they're used for.

Lasse

long, which is large integer

AttackingHobo

22:34

If you have a bad lag you can phase through walls

Icy Defiance

Lasse beat me

Ali.S

@AttackingHobo I've already finished that game many times (the cracked version, not proud of it)

radical

getTime retunrs number of ticks

getTimerRes returns number of ticks per second

Jimmy

ninja'ed

hasherr

Okay.

Ali.S

22:34

@AttackingHobo the only reason I've got to buy that game is to unlock it's achivements

Icy Defiance

@AttackingHobo only glitchy if you're not raytracing, and lag is a problem for fixed timestep games too

Lasse

the chat is getting hectic today

hasherr

Thanks guys

Icy Defiance

@Lasse mostly because of people giving bad advice, or only partly correct advice, and other people trying to correct them

Jimmy

sorry about that

Icy Defiance

22:35

nah it's nothing to be sorry for

it's just most people here weren't familiar with the problem

my statement did sound more insultive than I meant it to be

Lasse

and now when that's resolved, perhaps I should start planning my next game project

perhaps this is the one I get finished

AttackingHobo

@IcyDefiance I am talking about a specific game, SMB, which has the issue I am talking about. There are always ways around any issue but that dev did not solve the issues

radical

@hasherr, .. and since the result was < 1, 0.016..., converted to an int it became 0 . In case of B, both the operands were "raised"(treated as) double, so the result of division could be retained as is, with its fractional value (double represents a Real value)

Jimmy

I don't think I noticed any timestep glitches when I played SMB but I guess I'm used to games physics having "variable friction" by now

hasherr

@Lasse I'm on that one right now ;P

Ali.S

22:39

@IcyDefiance @AttackingHobo it was never laggy for me, the only problem I had was it sometimes didn't play any sound

Icy Defiance

@AttackingHobo fair, I just took the statement as a continuation of your arguments yesterday. maybe that wasn't the case.

Jimmy

just added another star to "integer division is bad for the soul" since apparently it wasn't starred enough times

Icy Defiance

lol right

John McDonald

hah, apparently

Icy Defiance

@Jimmy variable timestep doesn't exactly give variable friction. that's what happens when you either have variable timestep and don't account for it, or have fixed timestep and lag a little

the only variable with proper variable timestep code is the precision of floats or doubles, which is hardly noticable

jumping through walls is a problem when your framerate is too low and you're moving too far between collision checks, which is a problem with SMB

easiest way to solve that is raytracing

Jimmy

22:43

I dont' think I've ever going through a wall with smb

Icy Defiance

yeah me neither

your fps has to get pretty low

AttackingHobo

It was something happening in the backroudn that caused the game to almost freeze for a few seconds

on my old computer

Icy Defiance

that would do it

there were certain parts of the game that really did not run well compared to the rest of it

AttackingHobo

With a fixed timestep game it would just pause for a second or so

or freeze then catch up

or if designed bad enough spiral of death time!

Icy Defiance

but then you could do the thing in slow motion by intentionally limiting the resources it's allowed to use, effectively cheating your way through the game

Jimmy

22:47

would it just just catch up by iterating the updates?

Icy Defiance

if it was programmed well, it could

AttackingHobo

Icy I make my games pauses if it goes too low for too long

Icy Defiance

I'm hardly insulting fixed timestep. I'm just saying don't rely on it.

AttackingHobo

and most games are gpu bound anyways

Jimmy

well I mean, that's the fixed timestep loop I see used most often

AttackingHobo

22:48

I like multiplayer and replay systems

those are much harder with a dynamic timestep

Jimmy

like a simple version of the gafferongames version that doesn't keep track of the partials

Icy Defiance

@AttackingHobo they're also mostly not async, especially as far as indie games go, so where it's bound doesn't matter

crap, gotta move to class

I'll probably be back on momentarily

AttackingHobo

Anyone else here ever use Debugger Canvas? visualstudiogallery.msdn.microsoft.com/…

3

Icy Defiance

nope, but I'm saving that one

Grey

Dat looks cool

Icy Defiance

22:56

crap, my archive folder of bookmarks is getting way too big. I need to split it up again.

Shotgun Ninja

starred

AttackingHobo

Its pretty fucking awesome. It makes understanding the flow of the code so much easier

Grey

"Edit code directly on the canvas (including edit and continue if available) by enabling the option in the options dialog"

Dis

AttackingHobo

I have a program that is mostly in 2 files. each 600+ lines. this thing makes it so easy to edit it

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