Lua Programming Help Thread

[emericaska8r]

Ok, thanks jon frost. I'll try and look at it from here to make it better.

[natan333]

How is it stuck if the player it isnt touching and is not going to touch a block?
I'm gonna go back read over everything again. This is confusing me. Plus, the way you explain it (no offense) is not helping.

EDIT - OOOOOOHHHHH!! Ok. I get it now.

All right, you want it luaplayer to check if theres a block in the way of the player, and if there is, the player cannot go through it. Makes sense. It was harder to understand that since some parts of your post were repetitive.

Ok, umm...all right, heres an example:

-- box is 20x20 pixels
box_x = 100
box_y = 100
box2_x = 120
box2_y = 120

--[[this means the box will cover from:

 (100, 100)____________(120, 100)
|
|
|
|
|
(100, 120)_____________(120, 120) <bottom right of pic

]]

if player_x > box2_x or player_x < box_x and player_y > box2_y or player_y < box_y then 
can_move = true
end

if player_x >= box_x and player_x <= box2_x then
can_move = false
end

if player_y >= box_y and player_y <= box2_y then
can_move = false
end

does that help you?

not sure. becuase i m using

block = {}

block[1] = { x = 34, y = 190 }
for d = 2, 4 do
block[d] = { x = block[d-1].x + 16, y = 150 }
end

like the code bellow makes move up to be false if it touch the bottom of my 17x17 pixel box

for c = 1, 4 do
screen:blit(block[c].x, block[c].y, blockk)



	
	
if moving1 == true and x0 > block[c].x-14 and x0 < block[c].x+16 and y0+10 > block[c].y and y0 < block[c].y+17 then 
moving1 = false
end

---like in the code bellow, if the moving picture is at the left side of the box and bellow it, it becomes true


	
	
if moving1 == false and x0 < block[c].x-13 and y0 > block[c].y and y0 < block[c].y+17 then 
moving1 = true
end
end

but the problem is that if there is 3 boxs close with the same y axis but different x axis, the 1st at the right will work normally.
the 1st and 2nd of the left move up will be true because the 1st at the right is making it to be true

the thing i dont get it is to make it check if it have a box above the moving picture (that is x0 and y0)
so if there is a box above its false. if there is no box above its true for the moving picture to go up

[SG57]

so then do what your saying... its just booling really

[PSPduh]

I need some help.
Can someone explain me screen:drawLine to me VERY detailed? Because I need this to complete something that I'm making. Also, can somebody explain me screen:fillRect too? Thank you.
--PSPduh

[EminentJonFrost]

How do you call a variable from a table .. thats within a table?

What I mean by "how do I call it" is...well, ok, to call a variable from a table, you just do this:

table = { variable1, variable2 }
table.variable1 -- there, called the first variable from table "table".

so how would I call that same variable if its table were inside another table?

bigger_table = {
table = { variable1, variable2}
table2...blah blah
}

[emericaska8r]

Hey I was wondering what kind of software or whatever could create a .png image with a transparent background, so it wouldn't be all white, it would just be unnoticable. This is because I created one, yet when i saved it as .png my software said that it could save it in .png, yet it wouldn't retain all features. When i opend it again, it had a white, not transparent background. How would i do this?

[EminentJonFrost]

Hey I was wondering what kind of software or whatever could create a .png image with a transparent background, so it wouldn't be all white, it would just be unnoticable. This is because I created one, yet when i saved it as .png my software said that it could save it in .png, yet it wouldn't retain all features. When i opend it again, it had a white, not transparent background. How would i do this?

The GIMP.
To find it, go to Google.
dont worry, its free.

Ok, you need to get a runtime environment before the actual painting app, but its in the same site, so its not a problem.

all right now, once its installed, open it.
open up a photo. (its comes in it own window.)

on the top it says: File Edit Select ... blah blah
go to "Layer"
scroll down to "Transparancy"
to the side, go to "color to alpha"
then you pick a color in your image that will become transparent.
oh yea, it does .png pics. (and LOTS more.)

[Grimfate126]

How do you call a variable from a table .. thats within a table?

What I mean by "how do I call it" is...well, ok, to call a variable from a table, you just do this:

table = { variable1, variable2 }
table.variable1 -- there, called the first variable from table "table".

so how would I call that same variable if its table were inside another table?

bigger_table = {
table = { variable1, variable2}
table2...blah blah
}

i dont think youre even allowed to do that. i would just make two seperate arrays/tables.

[SG57]

Yes you are allowed... Not in LUA though... nad it sounds to me like your making a class, which is in C(?)/C++ so far...

But you can always do a multilayered table/array... I dunno if LUA supports it but...

example[3][3] = ( '1', '2', '3'
'4', '5', '6'
'7', '8', '9'
;}; example

Its something like that... that is for a tic-tac-toe board... so i dunno if LUA can support even this, let alone classes...

sorry, no help here =(

[EminentJonFrost]

thanks for trying.

but I know its possible.

Luaplayer's own game "snake" has this piece of coding in it to prove it:

...
-- possible options for menu
possibleOptions = {
	speed = {
		displayName = "Speed",
		values = { 1, 2, 3 } },
	level = {
		displayName = "Level",
		values = { "grass", "desert" } },
	music = {
		displayName = "Music",
		values = { "on", "off" } },
	sound = {
		displayName = "Sound",
		values = { "on", "off" } }
}
...

[Altair]

I think "example[3][1]" works (where [3] is the second table thats on the 3th place in the big table and [1] is the first value in the second table), but Im not completely sure.
Have you tried to just use: "bigtable.table1.valu e"? Maybe that works aswell.

[EminentJonFrost]

i thought about it, but no I havent tried that. I will right now...

edit - nevermind, I'm just gonna make a new table. I'll figure it out later.

One last thing, I have the enemy's "y" location set to math.random(272). making it appear randomly, but how come it appears at the same place everytime I start the game up?

[Grimfate126]

i thought about it, but no I havent tried that. I will right now...

edit - nevermind, I'm just gonna make a new table. I'll figure it out later.

One last thing, I have the enemy's "y" location set to math.random(272). making it appear randomly, but how come it appears at the same place everytime I start the game up?

put this at the VERY top of you code:

math.randomseed(os.time())

it should give you different numbers now.

[EminentJonFrost]

It worked!
But why?

[Grimfate126]

It worked!
But why?

that function make the random numbers based on the time, which isnever the same. without it, the psp ram recalls the number it got last time, cause it gets kinda "lazy". i dont relly know how to exxplain it, but hey, it works!

[slicer4ever]

^^what he said it's especially great for luawindows

[EminentJonFrost]

oh.
thanks for explaining it!

BTW, I think I found out how to call variables from tables that are inside tables.

"table name" [#] .(dot) "variable"

example:
a = { b, c = { d } }

a[2].d

[slicer4ever]

yes or like so:

table = {}
table[1] = {x = 5}
table[2] = {y = 6}

screen:blit(table[1].x,table[2].y,image)

i use mine this way(onle an example)

[EminentJonFrost]

yes or like so:

table = {}
table[1] = {x = 5}
table[2] = {y = 6}

screen:blit(table[1].x,table[2].y,image)

i use mine this way(onle an example)

that way looks easier. more organized, easier to find what you want.
I'll do it like that.

[slicer4ever]

it makes things much more easier as you said especially to understand everything

[Grimfate126]

that way looks easier. more organized, easier to find what you want.
I'll do it like that.

it would be eaiser to just do:

table = {}

table[1] = { x = 5, y = 6 }

screen:blit(table[1].x, talbe[1].y, image)

you dont need to create 2 tables.

[emericaska8r]

Yea, I downloaded The Gimp, yet when I try to save it with that transparent background it says because of .png capabilites, the layer must be merged, and then it doesn't save it with the invisible background? Any ideas? ???????

[TheMarioKarters]

Yea, I downloaded The Gimp, yet when I try to save it with that transparent background it says because of .png capabilites, the layer must be merged, and then it doesn't save it with the invisible background? Any ideas? ???????

If you're having problems with transparent backgrounds, PM me the images, i'll do it.

[Jeffery]

I need some help.
Can someone explain me screen:drawLine to me VERY detailed? Because I need this to complete something that I'm making. Also, can somebody explain me screen:fillRect too? Thank you.
--PSPduh

I'll explain them as best I can.


screen:drawLine

The syntax for screen:drawLine is as follows:

 screen:drawLine(x0, y0, x1, y1, color)

The x0 represents the starting "x" (horizontal) coordinates for a line.
The y0 represents the starting "y" (vertical) coordinates for a line.

The x1 represents the ending "x" (horizontal) coordinates for a line.
The y1 represents the ending "y" (vertical) coordinates for a line.

The color represents the color of the line.

EXAMPLE:

If I wanted to display a red line starting at the top left corner of the screen, and ending at the bottom right corner of the screen, I would use the following linesof code:

red = Color.new(255,0,0) 
 
x0 = 0 
y0 = 0
x1 = 480
y1 = 272
 
while true do
 
screen:drawLine(x0, y0, x1, y1, red)
 
screen.waitVblankStart()
screen.flip()
 
end

screen:fillRect

The syntax for screen:fillRect is as follows:

 screen:fillRect(x, y, width, height, color)

The x represents the "x" (horizontal) coordinates for the top left-hand corner of the rectangle that you want to fill with a color.
The y represents the "y" (vertical) coordinates for the top left-hand corner of the rectangle that you want to fill with a color.

The width represents the width (in pixels) of the rectangle that you want to fill with a color.
The height represents the height (in pixels) of the rectangle that you want to fill with a color.

The color represents the color that the rectangle will be filled with.

EXAMPLE:

If I wanted to fill a rectangle with the color red that starts at the top left-hand corner of the screen, and extends 200 pixels in both directions (vertical and horizontal), I would use the following lines of code:

 
red = Color.new(255,0,0) 

 
 
x = 0 
y = 0
width = 200
height = 200
 
while true do
 
screen:fillRect(x, y, width, height, red)
 
screen.waitVblankStart()
screen.flip()
 
end

Hope that cleared things up a bit. :icon_smil

[Altair]

Does anybody know if its faster to blit a whole image at once (so one big image) or two small slices? I need every bit of speed to be able to blit all the units.
If a unit moves, I need to delete the unit first and then blit it at the new position. I can delete the whole unit and blit it at the new place. OR I can delete only the part where it isnt anymore. But if it moves diagonaly it has to delete two slices (eg upper- and leftside).
I know its better to blit one big image then alot of smaller ones that form an image the same size. But im not sure if its the same if the smaller images have a smaller surface than the big one.

I hope its clear I tried my best.

BTW Why am I a PREMIUM Member suddenly? Thx to who ever made me one though!

[PSPduh]

I'll explain them as best I can.


screen:drawLine

The syntax for screen:drawLine is as follows:

 screen:drawLine(x0, y0, x1, y1, color)

The x0 represents the starting "x" (horizontal) coordinates for a line.
The y0 represents the starting "y" (vertical) coordinates for a line.

The x1 represents the ending "x" (horizontal) coordinates for a line.
The y1 represents the ending "y" (vertical) coordinates for a line.

The color represents the color of the line.

EXAMPLE:

If I wanted to display a red line starting at the top left corner of the screen, and ending at the bottom right corner of the screen, I would use the following linesof code:

red = Color.new(255,0,0) 
 
x0 = 0 
y0 = 0
x1 = 480
y1 = 272
 
while true do
 
screen:drawLine(x0, y0, x1, y1, red)
 
screen.waitVblankStart()
screen.flip()
 
end

screen:fillRect

The syntax for screen:fillRect is as follows:

 screen:fillRect(x, y, width, height, color)

The x represents the "x" (horizontal) coordinates for the top left-hand corner of the rectangle that you want to fill with a color.
The y represents the "y" (vertical) coordinates for the top left-hand corner of the rectangle that you want to fill with a color.

The width represents the width (in pixels) of the rectangle that you want to fill with a color.
The height represents the height (in pixels) of the rectangle that you want to fill with a color.

The color represents the color that the rectangle will be filled with.

EXAMPLE:

If I wanted to fill a rectangle with the color red that starts at the top left-hand corner of the screen, and extends 200 pixels in both directions (vertical and horizontal), I would use the following lines of code:

 
red = Color.new(255,0,0) 

 
 
x = 0 
y = 0
width = 200
height = 200
 
while true do
 
screen:fillRect(x, y, width, height, red)
 
screen.waitVblankStart()
screen.flip()
 
end

Hope that cleared things up a bit. :icon_smil

Thank you so much! :Punk: I'm copying that into notepad so I wont forget it.
EDIT: Is there a way to make a curved line? And no I can't use a preset one in an image, for the app I'm making.

[Jeffery]

I've kinda wondered how to do that myself, and I'll give it a try and see if I can come up with something. The only possible way that I can think of right now would be to draw every pixel in the curved line that you would want to create. Of course, that would take up a ton of lines of code.

[Altair]

It doesn't have to be a ton of code, depends on the curve. I just think it would go really slow, because it has to blit the curve pixel by pixel.

[PSPduh]

I found this in the lua snippet thread in the dev's dungeon:

Here's a function to draw a circle:

 
function drawCirc(where, x, y, radius, color)

	theta = 0

	while theta<=360 do
		where:drawLine((math.sin(  theta)*radius)+x, (math.cos(theta)*radius)+  y, (math.sin(theta+1)*radius  )+x, (math.cos(theta+1)*radius  )+y, color)
		theta = theta+1
	end
end

Even though it would draw a circle, at least it is curved. But maybe I could use a for loop to draw the curved line, so it wouldn't take up lines and lines of code. That's what the for loop is there for, to do a lot in a little lines of code.

EDIT: About screen:drawLine, do I need to use x0 y0 x1 y1? Because once you set them to what their equal to, then you can't change it. So can I do this:

screen:drawLine(10,10,90,100,red)

Can I use different variables besides x0 y0 x1 y1? <<<< Thats what I really mean.

[Jeffery]

Yep, you can use different variables or no variables at all (just the actual numbers).