Lua Programming Help Thread

[TacticalPenguin]

Why can't you just code the levels yourself?

[EminentJonFrost]

I need help with creating multiple lines...just for an effect. its basically 10-20 lines dashing horizontally simultaneuosly. my problem is trying to accomplish this without a large clunky repetitive script. i pretty much ripped what i have from Shine's starfield example because it has what i'm trying make, basically. it makes about 200 "stars" (white dots) with just 48 lines of code. its complexity loses me and i tried my best to get what i want out of it, but failed.

size = 200
zMax = 5
speed = 0.1

width = 480
height = 272

starfield = {}
math.randomseed(os.time())

function createStar(i)
	starfield[i] = {}
	starfield[i].x = math.random(2*width) - width
	starfield[i].y = math.random(2*height) - height
	starfield[i].z = zMax
end

for i = 1, size do
	createStar(i)
	starfield[i].z = math.random(zMax)
end

white = Color.new(255, 255, 255)
black = Color.new(0, 0, 0)

while true do
	screen:clear(black)
	for i = 1, size do
		starfield[i].z = starfield[i].z - speed

		if starfield[i].z < speed then 
			createStar(i) 
		end

		x = width / 2 + starfield[i].x / starfield[i].z
		y = height / 2 + starfield[i].y / starfield[i].z

		if x < 0 or y < 0 or x >= width or y >= height then
			createStar(i)
		else
			screen:pixel(x, y, white)
		end
	end
	screen:print(272, 264, "Starfield for PSP by Shine", white)
	screen.waitVblankStart()
	screen.flip()
	if Controls.read():start() then break end
end

now here's mine:

Line = {}

b = 1
c = 100
b2 = 11

function createLines(a)
	Line[a] = {}
	Line[a].x = b
	Line[a].y = c
	Line[a].x2 = b2
	Line[a].y2 = c
end

while true do
	screen:clear(black)

	pad = Controls.read()

	if pad:start() then
		break
	end

	screen:blit(0, 0, mbg)
	screen:print(100, 260, "Press Start to exit", white)

	for a = 1, 20 do
		b = b + 1
		b2 = b2 + 1

		if b2 == 479 then
			b = 1
			b2 = 11
		end
		createLines(a)
		screen:drawLine(Line[a].x, Line[a].y, Line[a].x2, Line[a].y, white)
	end

	screen.flip()
	screen.waitVblankStart()
end

my script just makes one line that goes way faster than its supposed to. does anyone get how to make it so the code makes 20 lines instead of one fast one?

[TacticalPenguin]

line = {}
lineimg = Image.createEmpty(1,12)
lineimg:clear(Color.new(255,0,0))
for i = 1,20 do
line[i] = {x = 10, y = 13*i, img = lineimg }
end
while true do
for i = 1,20 do
screen:blit(line[i].x,line[i].y,line[i].img)
line[i].x = line[i].x + 2
if line[i].x > 479 then line[i].x = 1 end
end
screen.waitVblankStart()
screen.flip()
end

That SHOULD make 20 lines that move across the screen from left to right and reset when they reach the edge of the screen.

[EminentJonFrost]

sweet! it does! i didnt want for them to be lined up vertically, but i'll fix that myself. but...can you explain that script to me, so i dont get this problem again...?

these two line in particular confuse me, as i havent used those functions ever before:

lineimg = Image.createEmpty(1,12)
lineimg:clear(Color.new(255,0,0))

EDIT - nvrmind, i pretty much figured it out after a little research and thinking. thanks for the help! :)

[myschoo]

well, first he "made" the line with Image.createEmpty(size)
then he cleared the line with white color

[TacticalPenguin]

Those lines are saying to the luaplayer:
1. Create an empty image that is 1 pixel wide and 12 pixels high.
2. Now clear it to the color 255,0,0 AKA red.
-= Double Post =-
For example:
bg = Image.createEmpty(480,272 )
bg:clear(255,255,0)
screen:blit(0,0,bg)
screen.flip
while true do
screen.waitVblankStart()
end

Thatll create an empty image the size of the screen., clear it to yellow, and blit it.

[EminentJonFrost]

i just figured that part out. lol

the only thing i have trouble with now is trying to spread the lines out..

EDIT - yes! i figured that out too...i just changed the number where the "X" is. i also changed the 'y' axis value.

for i = 1,20 do
	line[i] = {x = 25*i, y = 100, img = lineimg }
end

EDIT2 - hmm...i learned alot just now. i also didnt know that you could change "screen:clear()" to "whatever you want to specifically clear:clear()". lol

much appreciation for the help TacticalPaper and myschoo! :)

[TacticalPenguin]

random = Math.random(1,3)
line = {}
lineimg = Image.createEmpty(1,12)
lineimg:clear(Color.new(2 55,0,0))
for i = 1,20 do
line[i] = {x = 10, y = 13*i, img = lineimg }
end
while true do
for i = 1,20 do
screen:blit(line[i].x,line[i].y,line[i].img)
line[i].x = line[i].x + i*random
if line[i].x > 479 then line[i].x = 1 end
end
screen.waitVblankStart()
screen.flip()
end
-= Double Post =-
Thatll make them all move at different rates. If you want them all to move at the same rate but be space out, i can do that too.

[EminentJonFrost]

random = Math.random(1,3)
line = {}
lineimg = Image.createEmpty(1,12)
lineimg:clear(Color.new(2 55,0,0))
for i = 1,20 do
line[i] = {x = 10, y = 13*i, img = lineimg }
end
while true do
for i = 1,20 do
screen:blit(line[i].x,line[i].y,line[i].img)
line[i].x = line[i].x + i*random
if line[i].x > 479 then line[i].x = 1 end
end
screen.waitVblankStart()
screen.flip()
end
-= Double Post =-
Thatll make them all move at different rates. If you want them all to move at the same rate but be space out, i can do that too.

nice...it could look like a mini race. lol
i'll use that!

edit - dont worry about the spacing. i took care of that. thanks though

[myschoo]

random = Math.random(1,3)
line = {}
lineimg = Image.createEmpty(1,12)
lineimg:clear(Color.new(2 55,0,0))
for i = 1,20 do
line[i] = {x = 10, y = 13*i, img = lineimg }
end
while true do
for i = 1,20 do
screen:blit(line[i].x,line[i].y,line[i].img)
line[i].x = line[i].x + i*random
if line[i].x > 479 then line[i].x = 1 end
end
screen.waitVblankStart()
screen.flip()
end
-= Double Post =-
Thatll make them all move at different rates. If you want them all to move at the same rate but be space out, i can do that too.

this is great but i need it so it wont stay on that place....



this came out from 3 simple lines... how do i change it so i will only SEE those 3 lines and not like this? thx

[Ninjax1]

Were can I download lua for windows, so I can try out my code?

[EminentJonFrost]

right here:
http://www.luaplayer.org/

[TacticalPenguin]

1. Myschoo, sorry, I forgot to add in screen:clear. Here:
random = Math.random(1,3)
line = {}
lineimg = Image.createEmpty(1,12)
lineimg:clear(Color.new(2 55,0,0))
for i = 1,20 do
line[i] = {x = 10, y = 13*i, img = lineimg }
end
while true do
screen:clear()
for i = 1,20 do
screen:blit(line[i].x,line[i].y,line[i].img)
line[i].x = line[i].x + i*random
if line[i].x > 479 then line[i].x = 1 end
end
screen.waitVblankStart()
screen.flip()
end

Ninjax:http://www.luaplayer.org/luaplayerwindows-0.20.zip

[Ninjax1]

Erm, yeah. I downloaded that, and when I try to start my script it just starts some snake game...

[TacticalPenguin]

You need to delete the test.lua, and edit the Test cmd scxript to say:

luaplayer yourscript.lua

[slicer4ever]

or start cmd direct it to the folder which holds luaplayer than do:
luaplayer "file location"

[Ninjax1]

You need to delete the test.lua, and edit the Test cmd scxript to say:

luaplayer yourscript.lua

Thats great but it still won't run, as soon as I launch it, it shuts down. Is something wrong with my code?:

sprite = Image.load("ninja.png")

playerX = 0
playerY = 0

while true do

screen:clear()
pad = Controls.read()

screen:blit(playerX, playerY, sprite)

if pad:down() then
playerY = playerY + 1

if pad:up() then
playerY = playerY - 1
end

if pad:right() then
playerX = playerX + 1
end

if pad:left() then
playerX = playerX - 1
end

screen.waitVblankStart()
screen:flip()
end

[EminentJonFrost]

whats your (this is directed at everyone) method to stop the burst of speed that occurs when pressing a button? i merely put "screen.waitVblankStart(1 0)" to get around that, but that wont work so well with a game, as i just found out. the game slows to a crawl if i hold down a button when its coded like that. that way works fine otherwise (when the app isnt a game with things going on in real-time, so small delays dont seem like much at all).

i know theres one popular method that uses two variables, "oldpad" and "pad". can someone run that by me quick?

[Ninjax1]

It's not my code, this is what error I get (screen printed before it crashed):

[yaustar]

snake.lua is not in the same folder as luaplayer.

[Ninjax1]

snake.lua is not in the same folder as luaplayer.

Snake is the gay little game I got with lua, but I deleted everything related to it. My lua file is index, and it's not recognizing it...:Argh:

[slicer4ever]

if pad:down() then
playerY = playerY + 1

should be:

if pad:down() then
playerY = playerY + 1
end

[the undead]

ok im working on this game(cant discus it at the moment) but ive been trying hard and cant find a solution for my problem. I have a pic right, im tyring to get that pic go accross the screen(left to right, and right to left) at different y points(think like a grid...up and down)...but i need them to have collison(i have the function down, i just need to fill in some parts, when i get this part finished) If any one helps me they will be given the credit they diserve.

[slicer4ever]

simple whatever variable you blit it at say playerx then just increase it like:
playerx = playerx + 1
then if you want y checking just say:
if playery == 20 then playerx = playerx + 1 end

this is saying if the player's y is at 20 then increase his x by 1

[yaustar]

Snake is the gay little game I got with lua, but I deleted everything related to it. My lua file is index, and it's not recognizing it...:Argh:

In that case, you have not edited the run.cmd batch file to run index.lua.

[Ninjax1]

In that case, you have not edited the run.cmd batch file to run index.lua.

What run cmd?

[dracule]

I have a question... which is more efficient, setting up a function to move or just setting up an if statement

for example:

would this

if pad:up() then
movement(player1, up)
end

function movement(player, direction)
if direction==up then
dy=1
end
end

I would add more than that, that is just a very brief code that i wrote.

compared to this:

if pad:up()
p1.dy=1
end

the second one would be shorter for one player, but the one above it, the function movement can control more than one player, so i think it would be shorter in the long run, i think. can someone clear this up?

[EminentJonFrost]

its looks very much like the shorter one in the bottom is more efficient just from looking at it.

[myschoo]

You need to delete the test.lua, and edit the Test cmd scxript to say:

luaplayer yourscript.lua

better:

luaplayer yourscript.lua
pause

this stops right after it finds the error ;)

[TacticalPenguin]

Hey sweet, now I dont have to run it 10 times to get enough glimpses at the error to know what it is! Thanks myschoo!