Lua Programming Help Thread

[eldiablov]

hey guys. Im making a sort of little football (soccer) game. I want the first version to be fairly simple.

I want it so when the guy runs into the ball that it starts moving and eventually stops. I know how to do collision. I just wondered what i would type to make the ball move based on where the player collides with the ball.

[KleptoOne]

hey guys. Im making a sort of little football (soccer) game. I want the first version to be fairly simple.

I want it so when the guy runs into the ball that it starts moving and eventually stops. I know how to do collision. I just wondered what i would type to make the ball move based on where the player collides with the ball.

you could do a line projection path. Take the coordinates of the player and the coordinates of the ball and create a line formula. Then using that formula calculate a travel path and have the ball travel at whatever speed you like down that path. Gotta love algebra

[eldiablov]

i am good at algebra. Could you give me some sort of psuedo code or something?

Could you tell me at least how i would create this formula ?

[ahrimanes]

i am good at algebra. Could you give me some sort of psuedo code or something?

Could you tell me at least how i would create this formula ?

to take the angle the player got the ball you should use atan2

hitangle = math.atan2(playerx-ballx,playery-bally)
then based on that angle you can calculate the proyection path...
but its more complex.. you betther see the phicis of a pool game wher a ball hits another ball using ball 1 speed ball 2 speed, ball 1 mass ball 2 mass, and the hitangle to calculate the correct angle of proyection..
i recomend you to move the ball not whit ball.x = ball.x+1 bether to do like..

 ballangle = 45
 ballspeed = 5
 ballx = ballx+math.cos(ballangle)*ballspeed
 bally = bally+math.sin(ballangle)*ballspeed

thant should move the ball in angle 45 and whit a speed of 5
i strongly recomend to see pool game...

[eldiablov]

Ok. Any recommendations on where i can see something like this ?

With this way does it mean i dont need collision checks ?

[ahrimanes]

Ok. Any recommendations on where i can see something like this ?

With this way does it mean i dont need collision checks ?

of course you need colission chek,, but once it colide, you must calculate the ball new proyection angle. some interesting stuff on pool physics:
http://library.thinkquest.org/C006300/main.htm
here go to : momentum, collision , conservatin of the momentum.
read thiss too..
http://www.billiardworld.com/physics.html

well letme see for and example a did som years ago fo another language,,, or search for a pool game made in lua just read and read and test.

[youresam]

Ok. Any recommendations on where i can see something like this ?

With this way does it mean i dont need collision checks ?

Of course you do............

edit: nvm I was beat

[eldiablov]

thanks very much ahrimanes.

Im reading. Now.

I finished reading this one.
http://www.billiardworld.com/physics.html

and am looking at the formula on the other one but find them .... difficult.

[yaustar]

eldiablov: I recommend you use vector math instead, it is faster and once you have the base concepts, a lot easier to use.

Also, I wouldn't recommend trying to make this too realistic, ever played sensible soccer? Fake physics all the way and it was still enjoyable.

[eldiablov]

I dont planning on making it to realistic. Thanks Yaustar. I'll look at both and see which is easier to understand. :)

Yaustar im only getting vector for 3d games. Does this matter ?

[ahrimanes]

eldiablov check this out
http://www.phy.ntnu.edu.tw/ntnujava/...hp?topic=120.0
by the way im in the same position of Yaustar...
i think the ball must go foward whit the same angle of the player, then just make the speed alitel more big than the player.. and then the ball will lose speed simulating friction...
see this alogrithn

if collide (player, ball) then
ball angle =  player angle
ball speed  =  player speed * 1.5
end if
if ball speed > 0 then ball speed = ballspeed - 1
if ball speed < 0 then ball speed = 0

and calculate movemente of the ball like i show back there whit sin cos...

[eldiablov]

ty.

Loading takes long on java

reading this aswell.
http://physics.about.com/od/mathemat...ctorMath_4.htm

am i going in the right direction ?

[moncristo_da_dev]

is this correct?:
Timer = 0

while true do

pad = Controls.read()

if pad:cross() then
Timer = Timer.start()
end

if Timer == 10 then
player.y = player.y - 20
Timer = Timer.stop()
Timer = 0
end

[xpack]

youresam or anybody what would I do in creating the lrx for compressing and uncompressing zip files would anonymous tipster's .zip source help or is making lrx's for lua different...

[HaxxBlaster]

is this correct?:
Timer = 0

while true do

pad = Controls.read()

if pad:cross() then
Timer = Timer.start()
end

if Timer == 10 then
player.y = player.y - 20
Timer = Timer.stop()
Timer = 0
end

It should be like this:

Timer = Timer.new()

while true do
Timer:start()

pad = Controls.read()

if Timer:time() >= 10 then --I suggest you put the value 10 higher, because the timer counts  in milliseconds.
player.y = player.y - 20
Timer:reset()
end

end

[yaustar]

eldiablov: no. 3D is just 2D minus one dimension. Just leave the Z componment as 0.

[KleptoOne]

i am good at algebra. Could you give me some sort of psuedo code or something?

Could you tell me at least how i would create this formula ?

Just for fun, heres a way to do it using simple math.

Was thinking about this while at work and I worked out a fun simple math way of doing it. Definately not the best way, but I thought I'd share it.

You can just use the slope

ball.rise = (ball.y - player.oldy) 
ball.run = (ball.x - player.oldx)

I'm using an oldx and oldy variable to give me the point just before collision which will simulate force applied to ball. Longer the stride, the harder the ball will be hit.

Then its as simple as

ball.y = ball.y + ball.rise
ball.x = ball.x + ball.run

Slowing the ball down would be a little trickier, you would have to keep the ratios equal, so use a percentage formula.

if ball.rise > 0 then		--maintains motion direction
    ball.oldrise = ball.rise
    ball.rise = ball.rise - 1
elseif ball.rise < 0 then
    ball.oldrise = ball.rise
    ball.rise = ball.rise + 1
end
ball.run = math.floor((ball.rise * ball.run) / ball.oldrise)
if ball.rise == 0 then
    ball.rise = 0
    ball.run = 0
end

Just for kicks, vectors would be the best way though, a lot more control and accuracy. This method will cause shakiness in the slowdown. Just thinking outside the box.

[xpack]

Does anyone know how to get ahold of be2003 the creator of sysext.lrx (I think) Or get his source. I plan on improving the .zip compress and uncompress

[moncristo_da_dev]

It should be like this:

Timer = Timer.new()

while true do
Timer:start()

pad = Controls.read()

if Timer:time() >= 10 then --I suggest you put the value 10 higher, because the timer counts  in milliseconds.
player.y = player.y - 20
Timer:reset()
end

end

can i make it like this? i want it like that

Timer = Timer.new()

while true do

pad = Controls.read()

if pad:up() then
Timer:start()
end

if Timer:time() >= 10 then --I suggest you put the value 10 higher, because the timer counts in milliseconds.
player.y = player.y - 20
Timer:reset()
end

end

[youresam]

It should be like this:

Timer = Timer.new()

while true do
Timer:start()

pad = Controls.read()

if Timer:time() >= 10 then --I suggest you put the value 10 higher, because the timer counts  in milliseconds.
player.y = player.y - 20
Timer:reset()
end

end

lol good job. And even worse, I think you are restarting the timer every loop.
BTW, 2 line code:
timer = Timer.new(); timer:start()
screen:blit(player.x,player.y-timer:time()/10,player.img)

[SG57]

I cant really understand youresam's post, but what he's getting at is you've named a variable the name of a reserved class in Lua.

'Timer' is a reserved class of functions in Lua. Declaring a varaible named Timer will cause errors as you cant assign a class as a value.

Same with 'Music' and 'Sound' and 'screen' i believe...

Correct me if im wrong anywhere above.

[Jomann]

why wont you answer my pm sg57?

also if i have a cube:

cube = {
bla bla bla bal
ect ect ect cec
lol ol ol ol ol olol
}

how do i make it move forward and left and right?

add speed or lower speed, proper brakes?

or is there any 3d lua tuts out? i searched google and didnt find any

i am making a racing game :O

[Grimfate126]

why wont you answer my pm sg57?

also if i have a cube:

cube = {
bla bla bla bal
ect ect ect cec
lol ol ol ol ol olol
}

how do i make it move forward and left and right?

add speed or lower speed, proper brakes?

or is there any 3d lua tuts out? i searched google and didnt find any

i am making a racing game :O

dont take this personally, but if you cant figure out how to move a model, you're quite simply not ready to make even a bad racing game. also, you're not gonna find exact tutorials on every little thing. you need to learn the actual physics of cars, and apply that to your game. however, to asnwer your question:

you should have a vector of the cars position. like this: (its C, i havent worked with lua in some time)

ScePspFVector3 carPos = {0, 0, 0};

sceGumLoadIdentity();
sceGumTranslate(carPos);
// Draw Car //

now, to move it, its simply a matter of changing the coordinates, just as you would in 2D, but with an added dimension. like:

if (pressed right) {
carPos.x += speed;
}
etc.

also, keep in mind that the above example will not get you anywhere. you will also have to keep a direction vector, and use that to calculate the direction in which the car will move. i recommend reading the articles on gamedev.net

[Jomann]

hey im not dumb :P lol anyway thank you, i knew how to move the model but i didnt understand how to put it in my code thats why i put the cube = {}
thingy up there

[HaxxBlaster]

can i make it like this? i want it like that

Timer = Timer.new()

while true do

pad = Controls.read()

if pad:up() then
Timer:start()
end

if Timer:time() >= 10 then --I suggest you put the value 10 higher, because the timer counts in milliseconds.
player.y = player.y - 20
Timer:reset()
end

end

Sure. Is your point to make it move in one direction when you press a button?
Something like this?:

RT = Timer.new()
LT = Timer.new()
UT = Timer.new()
DT = Timer.new()

Speed=10

while true do

pad = Controls.read()

if pad:right() then
RT:start()
elseif pad:up() then
LT:start()
end


if pad:up() then
UT:start()
elseif pad:down() then
DT:start()
end

if RT:time() >= 200 then --I suggest you make the value 200 to fit, because the timer counts  in milliseconds.
player.x = player.x + Speed
RT:reset()
RT:start()
elseif LT:time() >= 200 then --I suggest you make the value 200 to fit, because the timer counts  in milliseconds.
player.x = player.x - Speed
LT:reset()
LT:start()
end

if UT:time() >= 200 then --I suggest you make the value 200 to fit, because the timer counts  in milliseconds.
player.y = player.y - Speed
UT:reset()
UT:start()
elseif DT:time() >= 200 then --I suggest you make the value 200 to fit, because the timer counts  in milliseconds.
player.y = player.y + Speed
DT:reset()
DT:start()
end

end

lol good job. And even worse, I think you are restarting the timer every loop.
BTW, 2 line code:
timer = Timer.new(); timer:start()
screen:blit(player.x,player.y-timer:time()/10,player.img)

I don't think it's what he want to do.

I cant really understand youresam's post, but what he's getting at is you've named a variable the name of a reserved class in Lua.

'Timer' is a reserved class of functions in Lua. Declaring a varaible named Timer will cause errors as you cant assign a class as a value.

Same with 'Music' and 'Sound' and 'screen' i believe...

Correct me if im wrong anywhere above.

I know, i think it works anyway. I've done it before. I remade the code.

[Anti-QuickJay]

How do you save a string with non-number elements in it?

[youresam]

I cant really understand youresam's post, but what he's getting at is you've named a variable the name of a reserved class in Lua.

'Timer' is a reserved class of functions in Lua. Declaring a varaible named Timer will cause errors as you cant assign a class as a value.

Same with 'Music' and 'Sound' and 'screen' i believe...

Correct me if im wrong anywhere above.

...you can name any variable anything, except for the programming-specific keywords...but...
Timer = Timer.new()
Do you not see something seriously wrong with that code?!

[Yongobongo]

How do you save a string with non-number elements in it?

blah = "blah"

..

[myschoo]

i have a text file like this:

code1 = 0
code2 = 0
code3 = 0
code4 = 0
code5 = 0

and now i need with file io save new value to code3, how would i do that??

[moncristo_da_dev]

Sure. Is your point to make it move in one direction when you press a button?
Something like this?:

RT = Timer.new()
LT = Timer.new()
UT = Timer.new()
DT = Timer.new()

Speed=10

while true do

pad = Controls.read()

if pad:right() then
RT:start()
elseif pad:up() then
LT:start()
end


if pad:up() then
UT:start()
elseif pad:down() then
DT:start()
end

if RT:time() >= 200 then --I suggest you make the value 200 to fit, because the timer counts  in milliseconds.
player.x = player.x + Speed
RT:reset()
RT:start()
elseif LT:time() >= 200 then --I suggest you make the value 200 to fit, because the timer counts  in milliseconds.
player.x = player.x - Speed
LT:reset()
LT:start()
end

if UT:time() >= 200 then --I suggest you make the value 200 to fit, because the timer counts  in milliseconds.
player.y = player.y - Speed
UT:reset()
UT:start()
elseif DT:time() >= 200 then --I suggest you make the value 200 to fit, because the timer counts  in milliseconds.
player.y = player.y + Speed
DT:reset()
DT:start()
end

end

I don't think it's what he want to do.


I know, i think it works anyway. I've done it before. I remade the code.

im just making a simple jump function