Star-field

[GEEK]

Hello! 
I'm looking for some code to make this: (picture)
I want to make a starfield screensaver in lua, but i'm not a genius in math :\
does someone want to help me?
Thanks in advanse

[Cosmo]

Hi Geek,

Code: [Select]

--'by Peter Wirbelauer
openwindow(640,480,0,"Stars")
setframetimer(60)

function rand(minZahl,maxZahl)
   maxZahl = (maxZahl-minZahl)
   return int(rnd()*maxZahl+minZahl)
end

local col=0;sx=0;sy=0;anz=5000;speed=2;xscreen=640;yscreen=480
local xstern ={}
local ystern ={}
local zstern ={}

for i=0,anz do
   xstern[i] = rand(-(xscreen/2), (xscreen/2))*128
   ystern[i] = rand(-(yscreen/2), (yscreen/2))*128
   zstern[i] = rand(speed,255)
end

function updatestars()
   local i,co
   for i=0,anz do
      zstern[i] = zstern[i] - speed
      if zstern[i] <= speed then zstern[i] = 255; end
      sx = (xstern[i] / zstern[i]) + (xscreen/2)
      sy = (ystern[i] / zstern[i]) + (yscreen/2)
      co = (300 -zstern[i])*.8
      alphachannel(250)
      color(co,co,co)
      box(sx,sy,sx+2,sy+2)
   end
end

repeat
k=getkey()
cls()
alphachannel(200)
updatestars()
redraw()
until k==27
closewindow()


[Cosmo]

another starfield.

Code: [Select]

--'by Peter Wirbelauer
openwindow(640,480,0,"Retro-Stars")
setframetimer(60)
colorkey(0,0,0)

function rand(minZahl,maxZahl)
   maxZahl = (maxZahl-minZahl)
   return int(rnd()*maxZahl+minZahl)
end

function sprite(id,x,y,w,h,fx)
   drawimage(w*fx,0,w,h,x,y,id)
end

local np=500; j=0; z=0; p=0; v=0
local px={}
local py={}
local pz={}

p = loadimage("png/phoenix.png")

for j=0,np do
    px[j] = rand(0,639)
    py[j] = rand(0,479)
    pz[j] = rand(65536,16777215)
end

repeat
k=getkey()
cls()
for j=0,np do
     px[j] = px[j] -1
     if px[j] <0 then
        px[j] = 640
        py[j] = rand(0,479)
     end
     color(pz[j],pz[j],pz[j])
     box(px[j],py[j], px[j]+2,py[j]+2)
end

sprite(p,(640-128)/2,(480-128)/2,128,128,z)

v = v+0.2
if v >=1 then
   v = 0
   z = z+1
   if z==10 then z=0; end
end

redraw()
until k==27
closewindow()


[Cosmo]

And once again.

Code: [Select]

--'by Peter Wirbelauer
openwindow(640,480,0,"Retro-Stars")
setframetimer(60)

function rand(minZahl,maxZahl)
   maxZahl = (maxZahl-minZahl)
   return int(rnd()*maxZahl+minZahl)
end

local rad = math.rad

local z = "HELLO AND WELCOME IN THE SUPER PROGRAMMING!"; letter=0
local fok, xp, yp, i, tl, x, m = 160,0,0,0,0,0,0
local x3DSterne ={}
local y3DSterne ={}
local z3DSterne ={}
local y ={}
local angle ={}
tl = len(z)

m=loadmusic("music/b.mod")
playmusic(m,128,-1)

for i=0,tl do
    angle[i] = 360-i*(360/tl)
    y[i] = 240
end

for i=0,799 do
    x3DSterne[i] = rand (1,440)
    y3DSterne[i] = rand (1,380)
    z3DSterne[i] = rand (1,500)
end

repeat
k=getkey()
alphachannel(150)
cls()
for i=0,799 do
    xp = (x3DSterne[i] * fok) / (z3DSterne[i] + fok) + 5
    yp = (y3DSterne[i] * fok) / (z3DSterne[i] + fok) + 5
    color(255,255,255)
    box(xp,yp, 2+xp,2+yp)

    xp = (-x3DSterne[i] * fok) / (z3DSterne[i] + fok) + 630
    yp = (-y3DSterne[i] * fok) / (z3DSterne[i] + fok) + 470
    box(xp,yp,2+xp,2+yp)

    xp = (-x3DSterne[i] * fok) / (z3DSterne[i] + fok) + 630
    yp = ( y3DSterne[i] * fok) / (z3DSterne[i] + fok) + 8
    box(xp,yp,2+xp,2+yp)

    xp = ( x3DSterne[i] * fok) / (z3DSterne[i] + fok) + 5
    yp = (-y3DSterne[i] * fok) / (z3DSterne[i] + fok) + 470
    box(xp,yp,2+xp,2+yp)

    z3DSterne[i] = z3DSterne[i] -1
    if z3DSterne[i] <=0 then
       z3DSterne[i] = 500
    end
end
alphachannel(255)

for x=1,tl do
   angle[x] = angle[x] +1
   if angle[x] == 360 then angle[x] =0; end
   letter = mid(z, x ,1)
   y[x] = y[x] + sin(rad(angle[x]*4))
   color(0x9C,0x5A,0xEF)
   drawtext(2+x*14,y[x],letter)
   y[x] = y[x] + cos(rad(angle[x]*2))
   color(0,255,0)
   drawtext(2+x*14,5+y[x],letter)
end

redraw()
until k==27
closewindow()


[GEEK]

wow!  that's sooo coool! 
thank you!

do you think you can give it the stripes effect?
that the stars like in the example are stripes?

I'm glad with this examples to! great 

[Cosmo]

Hi Geek,

stripes are possible with alphachannel, but unfortunately, Egsl alphachannel doesn't it.

[GEEK]

ok, thanks anyway! 

[GEEK]

Ow, the documentation says that egsl has alpha to...

[Cosmo]

Hi Geek,

Egsl has alpha, I know.
But what I meant was, that it doesn't work!  You cannot get stripes with EGSL_ALPHACHANNEL!

[Cosmo]

If you would peek into the source code, you would see that I used alphachannel!

[GEEK]

Yes, just saw that, sry.
can i ask you why you used "alphachannel(200)" then?
if i delete it, nothing changes...

repeat
k=getkey()
cls()
alphachannel(200)
updatestars()
redraw()
until k==27
closewindow()

and is it possible witout alphachannel? just stripes, pure white?

[Cosmo]

and is it possible witout alphachannel? just stripes, pure white?

I have tried, but without success. alphachannel in the source code is a holdover, I forgot to remove.
Alphachannel (50)  gets a darker white, but not alpha.   

[GEEK]

ok, going to mess a bit with that code, maybe i find a solution, thanks for the help! 

[Cosmo]

Hi Lelldorin,

Okay, you got it 

[GEEK]

Hi Lelldorin