Lua Programming Help Thread

[SG57]

distance = SQUARE ROOT ( (x2 - x1)^2 + (y2 - y1)^2) )

The angle angle between to points? You could get the slope, plot the hypotetnues and use sine/cosine or tangent to get the angle.

[Cheez Pirate]

name:blit(whatever)

This is from animlib. What do I put in the whatever section? Actually all I need to know is how to blit animations.

[Grimfate126]

this is more of a general programing question, but how do you get the angle and distance between 2 points, (x1,y1,x2,y2).

angle = atan2(x2-x1, y2-y1)

[BlackShark]

name:blit(whatever)

This is from animlib. What do I put in the whatever section? Actually all I need to know is how to blit animations.

easy one,...
example:blit(0, 0. 100)

"name" of animation : "blit" obvious, (X, Y, "time between frames")
the time between frames is how fast the animation is (or slow) the higher the number the longer the pause.


NOW FOR MY QUESTION

I KNOW this has came up b4, but how EXACTLY do you fade in and Out? im having troubles...

[Grimfate126]

they should seriously put animlib functions in the function reference area on the lua wiki site. im getting 50 pms every day.

@ BlackShark- 1 sec, lemme write an example
-= Double Post =-
@ BlackShark:

heres a demo, havent tested it, but it should work:

test = Image.load("test1.png")
bg = Image.createEmpty(480, 272)

speed = 1
fade = 255

while true do

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

if fade >= 0 then
	bg:clear(Color.new(0,0,0,fade))
	screen:blit(0,0,bg)
	screen:blit(0,0,test)
	fade = fade - speed
end

screen.flip()
screen.waitVblankStart()
end

[BlackShark]

ok, thanks a bunch! going to test it now( also much thanks for animLib! animations would really suck without it...)
-= Double Post =-
Damn, does not seem to work, I tried switching the blit positions of bg and my image but that didn't work neither
what i mean by that is i took

screen:blit(0, 0, bg)
screen:blit(0, 0, contest)

and stitched them.... cuz other wise the "contest" image would blit on top of the fader, but that still didn't work..

[Grimfate126]

ok, thanks a bunch! going to test it now( also much thanks for animLib! animations would really suck without it...)
-= Double Post =-
Damn, does not seem to work, I tried switching the blit positions of bg and my image but that didn't work neither
what i mean by that is i took

screen:blit(0, 0, bg)
screen:blit(0, 0, contest)

and stitched them.... cuz other wise the "contest" image would blit on top of the fader, but that still didn't work..

what do you mean by "doesnt work"?

also, are you trying this on windows lua?

[BlackShark]

Y? is it psp luaplayer Only? in that case ill try it out on my psp!

[Grimfate126]

Y? is it psp luaplayer Only? in that case ill try it out on my psp!

windows lua doesnt support transparency, so even if it did work, it wouldnt look like it.

[BlackShark]

Cool, it works, any idea on how to fade out?

[SG57]

I use this in all my games (in LUA so far) to fade from black to an image, then wait for abutton to press, then to fade from that image to black.

-- get rid of any display buffer resido from game menu
screen:clear()
screen.waitVblankStart()
screen.flip()

--  Intro
bg_music = Sound.load("Sound/menu.wav",true)
music = bg_music:play( )
bullet = Sound.load("Sound/bullet.wav")
reload = Sound.load("Sound/reload.wav")
click = Sound.load("Sound/enemy_fire.wav")

intro = Image.load("GFX/logo.png")
fader = Image.createEmpty(480,272)
alphaValue = 255
faderColor = Color.new(0,0,0,alphaValue)
fader:clear(faderColor)
while true do
	screen:clear()
	screen:blit(0,0,intro)
	screen:blit(0,0,fader)
	faderColor = Color.new(0,0,0,alphaValue)
	fader:clear(faderColor)
	screen.waitVblankStart()
	screen.flip()
	if alphaValue > 0 then
		alphaValue = alphaValue - 1
	else
		break
	end
end
while true do
	blah = Controls.read()
	if blah:cross() or 
	   blah:circle() or 
	   blah:square() or
	   blah:triangle() or 
	   blah:start() or 
	   blah:select() or 
	   blah:left() or 
	   blah:right() or 
	   blah:down() or 
	   blah:up() or 
	   blah:l() or 
	   blah:r() then 
	   	break 
	end
end
while true do
	screen:clear()
	screen:blit(0,0,intro)
	screen:blit(0,0,fader)
	if alphaValue < 255 then
		alphaValue = alphaValue + 1
	else
		break
	end
	faderColor = Color.new(0,0,0,alphaValue)
	fader:clear(faderColor)
	screen.waitVblankStart()
	screen.flip()
end

Just copy the fade in or out code to sepearte the 2. But make sure you make the alphaValue = 0 when fading out, and 255 when fading in.

[Cheez Pirate]

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

dofile("lib/animlib.lua")

logo = ANIM.new(8,"logo","png","logo/")

loadingscreen = Image.load("images/loadingscreen.png")
   
loadingbar = {}
loadingbar.y = 12

data = {}
data.loaded = 0

cursor = Image.load("images/cursor.png")
data.loaded = data.loaded + 25 * 4

nameofimage = nil

while true do

	pad = Controls.read()
	screen:clear(white)
	logo:advancedBlit(0,0,500,1)
	logo:free()
	screen:clear(white)
	screen:blit(0,0,loadingscreen)
	screen:fillRect(47,205,data.loaded,loadingbar.y,red)
	screen.waitVblankStart()
	screen.flip()
end

It won't load the begining animation. It seems like it just skips it. Then it goes directly to the load menu and in less than half a second it disapears and says I have an error on lib/animlib.lua:130: and the loading menu doesn't use animlib. But the logo does. (the very first thing that shows up. The animation.)

[SG57]

Want to know why?

while true do -- START of loop 

	pad = Controls.read()
	screen:clear(white)
	logo:advancedBlit(0,0,500,1) -- draw animation
	logo:free() -- free animation before even flipping the screen
	screen:clear(white)
	screen:blit(0,0,loadingscreen)
	screen:fillRect(47,205,data.loaded,loadingbar.y,red)
	screen.waitVblankStart()
	screen.flip()
end -- end of loop - go back to START of loop

SEe the problem?

[BlackShark]

Uber cool, it works, thanks SG57 and GrimFate! very helpfull.

[Cheez Pirate]

so i put screen.flip() before freeing the animation and after blitting it?

[BlackShark]

I believe so..

[Yongobongo]

Has anyone got any AI tuts? I'm at a dead loss

[BlackShark]

Has anyone got any AI tuts? I'm at a dead loss

I second this, specifically space shooter kind of AI with enemies firing..

[Yongobongo]

Check your PM blackshark, the chart by Vaza is a good resource ;)
Anyone who knows of AI tuts/snippets, i would still really like to see them as my code is very basic, and kind of crappy

[yaustar]

Yongobongo: I gave you this 2-3 pages back

Here is a start. Look around Gamedev for more or get a good book: http://www.gamedev.net/reference/art...article784.asp

Here is the complete listing from GameDev.
http://www.gamedev.net/reference/list.asp?categoryid=18

There are also tons at http://gamasutra.com

[ZereoX]

Here this is my code:

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

function playerMovement()

Player = {X = 0, Y = 0, Health = 18}

if pad:left() then
Player.X = Player.X - 8
elseif pad:right() then
Player.X = Player.X + 8
elseif pad:up() then
Player.Y = Player.Y - 8
elseif pad:down() then
Player.Y = Player.Y + 8
end

end


while true do

pad = Controls.read()

playerMovement()

screen:print(Player.X,Player.Y,"@",blue)

screen.waitVblankStart()
screen.flip()
end

but as you can see its printing a moving text...But when i press a every direction ones I end up with 5 "@" and it won't go further like EG:
->@
@@@ and when i press further more then once nothing happends.
->@

SO I want to know how do I erase other "@" as I press and How to make I go Further then only once.

[TacticalPenguin]

After while true do put screen:clear(). And to keep him onscreen, you can do one of two things. Edit hiks movement or put boundaries.

[yaustar]

In function playerMovement, you set the player's position to 0, 0 every time the function is called.

[eldiablov]

Hi my game is near release *fingers crossed* but i have one problem. When he goes over the cheese and score goes up 1 i want the cheese to go to another random position. Anybody got tips on how to do this ?

[GuitarGod1134]

Hi my game is near release *fingers crossed* but i have one problem. When he goes over the cheese and score goes up 1 i want the cheese to go to another random position. Anybody got tips on how to do this ?

Simple

If player over the cheese then
cheese.x = math.random and cheese.y = math.random
end

Basically when he hits that cheese and you get the score then you redeclare the cheese's coordinates to... whatever you want in your case a random number.

[Cheez Pirate]

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

dofile("lib/animlib.lua")

logo = ANIM.new(8,"logo","png","logo/")

loadingscreen = Image.load("images/loadingscreen.png")
   
loadingbar = {}
loadingbar.y = 11

data = {}
data.loaded = 0

cursor = Image.load("images/cursor.png")
data.loaded = data.loaded + 25 * 4

nameofimage = nil

while true do

	pad = Controls.read()
	screen:clear(white)
	logo:advancedBlit(0,0,500,1)
	screen.flip()
	screen:clear(white)
	screen:blit(0,0,loadingscreen)
	screen:fillRect(47,205,data.loaded,loadingbar.y,red)
	screen.waitVblankStart()
        screen.flip()
end

Everything loads. But at the same time. I know it's because of the 2 screen.flip()'s but I can't fix it. I put "end" behind the first screen.flip() and that doesn't work either.

[eyece]

Has anyone got any AI tuts? I'm at a dead loss

it depends on how to have programed your game.

whats the function name for getting the square root, i remember seeing it somewhere, somthing like math.squrRoot()

[Grimfate126]

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

dofile("lib/animlib.lua")

logo = ANIM.new(8,"logo","png","logo/")

loadingscreen = Image.load("images/loadingscreen.png")
   
loadingbar = {}
loadingbar.y = 11

data = {}
data.loaded = 0

cursor = Image.load("images/cursor.png")
data.loaded = data.loaded + 25 * 4

nameofimage = nil

while true do

	pad = Controls.read()
	screen:clear(white)
	logo:advancedBlit(0,0,500,1)
	screen.flip()
	screen:clear(white)
	screen:blit(0,0,loadingscreen)
	screen:fillRect(47,205,data.loaded,loadingbar.y,red)
	screen.waitVblankStart()
        screen.flip()
end

Everything loads. But at the same time. I know it's because of the 2 screen.flip()'s but I can't fix it. I put "end" behind the first screen.flip() and that doesn't work either.

whats the problem?????

[Cheez Pirate]

Well it will load everything without errors but it will load and blit both the loading screen and the animation at the same time. And the screen will flash while doing so.

[TacticalPenguin]

Because its repeating it in a while true do.