Game Development

12:50 AM

Does anyone have any links for some tutorials on 2D Game Physics?

Just got done making a nice long descriptive answer for this question gamedev.stackexchange.com/questions/23027/… and the author deletes it before I finish :(

Code Assasssin

lol :(

ClassicThunder

32

Q: Resources for 2d game physics

I'm looking for some good references for learning how to model 2d physics in games. I am not looking for a library to do it for me - I want to think and learn, not blindly use someone else's work. I've done a good bit of Googling, and while I've found a few tutorials on GameDev, etc., I find the...

c# game-development f# 2d physics

Code Assasssin

Thanks ClassicThunder! :D

ClassicThunder

np

thedaian

12:59 AM

@ClassicThunder bonus round: he reposted it on SO: stackoverflow.com/questions/9042009/…

ClassicThunder

saw that and left a nasty comment

lol

ass

hahaha

Is anyone here familiar with SDL... I still haven't got this bullet thing to work.. :/

Its really getting under my skin now... I haven't made progress on my space shooter for days

:l Meh

thedaian

1:11 AM

I am

Post code or something

Code Assasssin

:D Oh sweet

Oh alright

Um, just to let you know, My code may seem ridiculously confusing... :(

Im not that good at C++ :L

thedaian

at worst, it's probably as bad as mine

maybe worse.

Code Assasssin

lol

ClassicThunder

thats what you get for using C++

Code Assasssin

Lol, so C++ is bad?

or hard?

thedaian

1:14 AM

Yes

Code Assasssin

Yeah, it can be a bit challenging at sometimes.... It's my first programming language so, I expect it to be hard :)

if(spacebar)
{

int frame2 = 0;

if(once2 == 0)
{
projectilex2 = x + 19;
projectiley2 = y + -35;
projectilex3 = x + 19;
projectiley3 = y + -35;
}

if(frame2 == 3)
{
frame2 = 0;

}

apply_surface(projectilex2,projectiley2,ShootStuff,screen,&lazers[0]);

frame2 ++;
projectiley2--;

once2++;

apply_surface(projectilex3 - 4,projectiley3,ShootStuff,screen,&lazers[0]);
projectiley3--;

if(once2 == 250)
{
once2 = 0;
spacebar = false;
}

}

O_o

Okay, thats my shoot function... It works as expected except, I cant get it to rapid-fire or anything

For example if I hit the spacebar(and continue holding it) I want the ship to fire bullets until the user releases his hand or something

But... Whenever I hit spacebar, I have to wait until the first bullet clears to draw another one

thedaian

uhh... use pastebin.com or something....

Code Assasssin

Oh sorry :l

Im a noob :P

thedaian

also, first programming language. C++ is bad for that. like, really bad for that :(

ClassicThunder

they should have the same formatting here as for the answers :/

thedaian

1:18 AM

you can do "fixed width" on chat messages, but it isn't obvious, and it still doesn't look as pretty

Code Assasssin

pastebin.com/ykDWEV9s

thedaian

though, @CodeAssasssin, if you're code hasn't changed from when you asked your original question, I can look at that, too....

Code Assasssin

Yeah, you can, I really didn't get the vector thing they suggested to do :l

thedaian

also you accepted an answer on your "multiple bullets on screen" thing...

yeah

Code Assasssin

Yep. I really just gave up

thedaian

1:20 AM

this is why C++ is bad for first language :(

Code Assasssin

:L

Lol

Yeah. But, Im too far in to quit now :D

thedaian

ok.

Code Assasssin

Hmm... I dont think I have any comments in my shoot function, so I'll see If I can explain a few things

thedaian

i think i can figure out the basics

Code Assasssin

kk

thedaian

1:23 AM

but... might be easier to see all your code. is it in one giant file?

Code Assasssin

Yep. Im too lazy to separate it all in one file

* seperate files

Do you want me to give you my main.cpp?

thedaian

yeah, that'd be easier, i think

Code Assasssin

kk

thedaian

though based on the small amount of code there, you're going to have to at least use an array to start with

Code Assasssin

pastebin.com/gbXc888U

Thats everything

thedaian

1:31 AM

ok, let's start simple. do you know what an array is?

Code Assasssin

Im pretty sure its a way to store elements

or numbers

It's a bit like a vector only C-styled?

thedaian

well. sort of. do you know what a vector is?

Code Assasssin

Same thing as an array?

thedaian

see, now we're just going in circles :P

Code Assasssin

:P

Ah alright

A vector is.... idk

lol

thedaian

1:33 AM

ok, that's fine

so, what is an array?

Code Assasssin

An array is something that can store elements or numbers?

Im not sure

thedaian

or possibly simpilier, do you know what variables are?

Code Assasssin

Of course

thedaian

alright. what are they?

Code Assasssin

Variables are integers,floats, etc

thedaian

1:35 AM

ok, what do they do?

Code Assasssin

:/ They allow the user to assign them specific values for computation etc

thedaian

alright, good an explaination as any

so you can store numbers and stuff in variables

now, an array is a way to keep track of a lot of variables at once

Code Assasssin

Thats more efficient than declaring a bunch of variables :). Thanks for the explanation

thedaian

something like int bullets[10] will let you store a list of 10 integers

Code Assasssin

That allocates space for 10 integers in the array bullets,right?

thedaian

1:38 AM

and you can access invididual values in an array by using bullets[0]; bullets[1] etc.

yep

Code Assasssin

Mhm

got it

thedaian

now. objects. do you know what those are?

Code Assasssin

Yep, they are things that give access to a classes functions

?

thedaian

sure, we'll go with that. now, what are classes, then?

Code Assasssin

Ways to store functions and variables for certain things/entities in your program?

thedaian

1:41 AM

yes.

Code Assasssin

:-)

thedaian

(there's more to all these things, but for the basics, this is good enough)

so, in the answer of the question you asked, the person mentioned creating a class for the bullet

that would let you store stuff like location, and whatever else, in a single spot

Code Assasssin

Yep, I would probably need access to the player class so I'd probably do something like this:

class Bullet: public Player

???

thedaian

nah

Code Assasssin

? Really?

thedaian

1:44 AM

you don't want to have the bullet class inherit from the player class.

that's really bad

Code Assasssin

:L

How so?

thedaian

easiest way would be to have Bullet be in it's own class, and then give the player class an array of, say, 10 bullets

aka: Bullet bullets[10]; in the Player class definition

Code Assasssin

Hmm

Alright

Let me make the class now... brb

Alright I've made the separate bullet class, so now I need the array right?

thedaian

yes

Code Assasssin

should this be under private or public??

I'm guessing private

thedaian

1:48 AM

eh, doesn't matter too much, but private would be a bit better.

Code Assasssin

I agree

Alright, bullet[10] array is done

thedaian

(actually thinking about it even more, i messed up. put the bullet array in your main game loop program part, accessing everything via the Player is going to be a problem)

Code Assasssin

Alright, so I'm going to take the bullet array to the main game loop(the while statement in the main function), and keep the Bullet Class?

Kk, its in my loop

thedaian

keep the Bullet class, put the bullet array declaration after this line: buttonsound = Mix_LoadWAV( "ButtonSound.wav" );

keep it outside of the actual loop

Code Assasssin

sorry about that

Internet these days

thedaian

1:54 AM

not a problem

Code Assasssin

anyway

I put the array below that statement

thedaian

alright. so, now we need to do something with those bullets

Code Assasssin

Position them? Move them? Then show them?

thedaian

yeah

Code Assasssin

Hmm... doesnt that mean I would need access to the ships coordinates? Its coordinates are privates... :(

thedaian

1:57 AM

probably, yes

Code Assasssin

and they aren't global.

thedaian

there's two solutions

make the coordinates public, or make a function that returns the coordinates

the latter is technically better

Code Assasssin

Function?

Hmm maybe I should just make it global, idk

thedaian

don't make it global

it'd be better to make the coordinates public than make them global

Code Assasssin

kk

so its public: int x,y

thedaian

2:00 AM

yep, that'll work

Code Assasssin

then make another pair of variables exactly the same but global?

thedaian

why global?

Code Assasssin

Ah never-mind, kinda lost track for a moment :P

*got off-topic

thedaian

hmmm, alright, another thing, your player should not be where you handle input

move that to your main loop function (where you currently call p.handle_input())

feel free to turn your player velocity stuff public when you do that, because seriously who cares?

Code Assasssin

@thedaian Which piece of coed should I move?

*code

When you say the player should not be

where I handle the input to move?

thedaian

2:07 AM

everything in Player::handle_input() should be in p.handle_input();

Code Assasssin

kk done

thedaian

alright. everything still compiles and works, right?

Code Assasssin

okay it's saying that bullet was not declared in this scope

My array is currently acting up :P

Hold on

bullet[10];

Weird... does that array look strange to you?

thedaian

if that's all you have on that line, then that's not going to work

Code Assasssin

set_clips(); //Make the button
set_clips2();
Button myButton( 190, 230, 254, 58);
ExitButton myExitButton(195,360,241,54);
buttonsound = Mix_LoadWAV( "ButtonSound.wav" );
bullet[10];

thedaian

2:14 AM

yeah

Code Assasssin

This part right here. :l

thedaian

you need a type for that bullet[10];

Code Assasssin

Okay, confused....

thedaian

something like Bullet bullets[10]

Code Assasssin

kk it works

Everything compiles fine.

thedaian

2:16 AM

hooray

Code Assasssin

lol

thedaian

alright, the next part is getting those 10 bullets to do something

Code Assasssin

Totally stuck and confused on that part :( Haven't dealt with arrays like this before

thedaian

assuming you have a function like Bullet::show() to display them, you need to now loop through the array to call that function

Code Assasssin

hmm, so something like in the Bullet::show function

Do this:

for (int i; i < bulletsize; i++)

{ bullet[i] }

?

thedaian

2:22 AM

kind of sort of not really at all

Gtoknu

Hello ppl

Hey code assassin, got you shooting game to work?

Code Assasssin

No :L

Lol

thedaian

right now, that bullet[10] is 10 Bullet objects

Gtoknu

seems that thedaian is helping you, that's nice.

Code Assasssin

kk

so the array bullet has 10 object that store the bullets

Gtoknu

2:23 AM

Hey @thedaian, won't be better to use a array of pointers, or a list of pointers?

thedaian

@Gtoknu yes, but also harder

Gtoknu

hm, maybe

thedaian

@CodeAssasssin is learning C++ as his first language (bad idea), so pointers... let's not even go there

Code Assasssin

Lol true

thedaian

we're doing this as "babbies first code" example

Code Assasssin

2:24 AM

Lol, I can do pointers :)

Im not that bad

Gtoknu

@CodeAssassin What are pointers, how can you allocate those and how can you delete those?

thedaian

from what i've seen, you are :P

Code Assasssin

:P Give me a break, Im taking this on at 12 years old

Most of this stuff is "magic"

Gtoknu

Nah, a good age. I Learnt C++ with 11 also.

thedaian

let's ignore pointers. it's not worth it

Code Assasssin

2:26 AM

Ah fine

Gtoknu

yup

Code Assasssin

Alright, so looping through the array, how's that going to be done?

thedaian

(seriously after you get this done, learn basic programming wit python or javascript or something, because you really need to learn the basics before jumping into copy/pasting from lazyfoo.com's tutorials)

Code Assasssin

Lol

Yep

That was meant as something to start em off

*me

thedaian

you got the basic loop code when you mentioned it.

for (int i=0; i < 10; i++)
{ bullet[i].show(); }

stick that after p.show();

Gtoknu

2:28 AM

Hey, I'm a little out of time now, but, daian, try to explain my answer to him: gamedev.stackexchange.com/questions/22616/sdl-bullet-movement/…

would save you some time, maybe.

thedaian

@Gtoknu that answer would work.... but it's also pretty advanced stuff

Gtoknu

Just change the list to an array

even then

kk

omg haha

2:31 AM

@theda

??

Wtheheck

O_o

srry

thedaian

@Gtoknu seriously, @CodeAssasssin is at programming 101 here, your code and answer is good, but it's going to be hard to understand

Code Assasssin

typo

Gtoknu

@CodeAssassin, Where are you from, btw? those "kk" laughs are pretty common here in brazil, and pretty uncommon outside here.

Code Assasssin

California :D

Gtoknu

@thedaian No prob, we can try to teach something more easy to understand to him :)

thedaian

2:32 AM

i believe 'kk' is "ok, ok"

Code Assasssin

Hmm, isnt it okay

not okay,okay

Gtoknu

almos EVERY people that live in here and use internet laugh as "kkkkkkk"

Code Assasssin

?

Gtoknu

I don't understand why, but they do.

Code Assasssin

I thought that was lol, and rofl

:)

Gtoknu

2:33 AM

yep, it is.

But I didnt know that it meant that outside here too.

Anyway, what you got so far, @CodeAssassin?

Code Assasssin

Nothing much yet(we have a separate bullet class, and an array that holds 10 bullets), thedaian is just walking me through this

Gtoknu

Nice

That's pretty much, considering you just need now to add a bullet to the array when you press space, and remove one when it collide with something

Code Assasssin

Yeah, I cant do removing now... I don't have collision yet.

Gtoknu

Well, you can at least remove when it reaches out of screen

that's easy

Code Assasssin

Yeah

@thedaian I'm honestly not that bad at C++ :P. I've been using SFML for 3 months and I had no problems with that. A friend just told me to use SDL instead of SFML.

Gtoknu

2:40 AM

SDL is more "low level"

but it is pretty nice also, but to that, you should know very well what you're doing

Code Assasssin

Yeah, I think Physics and math is my problem :l

Gtoknu

You'll see that this is not the biggest problem with game dev.

Code Assasssin

Hmm, In you opinion what is?

*your

Gtoknu

There's no "hardest part"

but there's the "boring" parts

Code Assasssin

Lol

Gtoknu

2:43 AM

I mean, everything if you think a little, you could get an answer very fast.

And there are A LOT, of resources in the internet.

For example. "Oh, I want to add gravity to my game." You can see with a little googling that gravity is just something that accelerate you downward at 10m/s^2

Code Assasssin

I dont even understand that

10*m

/s(squared)?

Gtoknu

Ah

Code Assasssin

whats the m and s stand for o.o

Gtoknu

meters

10 meters per second per second

There's no big problem here. When I was younger, I was used to do a lot of math that i didn even understand. When I get in the Highschool, I got to understand the most part of the physics of a game.

Code Assasssin

Too bad, Im in 7th

:L

Gtoknu

2:47 AM

A lot of your friends will say on the class "I wont ever use that on my whole life!" You'll see that a lot of your teachers are teaching, you already done it before in a game.

Code Assasssin

Yep

Gtoknu

That is what I realized when i "learnt" in the school functions, matrix, vectors, gravity, etc etc.

Code Assasssin

Meh, I have a lot of work to do :-)

Gtoknu

Yep (:

It's nice to see someone starting in the game dev early in life

Code Assasssin

Lol, you too. Your 15, I'm surprised :D

Gtoknu