Electrix Stars

[kevin]

    Electrix 2D Stars

        Here's a quick mock up of an effect found in the winning Amiga demo from revision 2016.    The effect moves a bunch of stars, where  each star has a glow / luminance value computed from the nearest star which are then linked via alpha additive lines.. 

          This version contains an ugly nested (squared) loop to find near by stars.. you can get rid of most of it by shuffling the array, which is a lot less expensive...   

 
    Video

    Source Code

PlayBASIC Code: [Select]

;*=-----------------------------------------------------------------------------=*    
;
;                                    >> Exlectric Stars <<
;
;                                  By Kevin Picone
;
;                            Built Using PlayBasic V1.65 beta2
;
;                  Copyright 2016 by Kevin Picone All Rights Reserved.
;
;*=-----------------------------------------------------------------------------=*    
;                            www.UnderwareDesign.com  -  www.PLayBASIC.com
;*=-----------------------------------------------------------------------------=*    

    ; Include the Blit Image functions
      #Include "BlitImage"


    ; Compute a 16 by 9 screen size. 
    ScreenWidth    =960
    ScreenHeight=ScreenWidth*(9.0/16)
    
    if ScreenWidth<>GetSCreenWidth()
        if ScreenHeight<>GetSCreenHeight()
            OPenScreen ScreenWidth,ScreenHeight,32,1    
        endif
    endif


    ; Define the basic star structure
    TYPE tStars
                X#,Y#
                Speed#
                Direction#
    EndTYPE
    
    Size=250
        
    Dim Stars(Size) as tStars

    ; fill the array with starting data
    For lp =0 to size
            Stars(lp)                = new tStars
            Stars(lp).x                =rndrange(-100,ScreenWidth+100)
            Stars(lp).y                =rndrange(-100,ScreenHeight+100)
            Stars(lp).speed        =rndrange#(2,7)
            Stars(lp).Direction    =90
    next

    ; create the screen sized FX buffer 
    Screen=NewImage(ScreenWidth,ScreenHeight,2)


    ; ---------------------------------------------------------------
    Do
    ; ---------------------------------------------------------------

            ; draw to the FX screen
            rendertoimage screen
    
            ; Ink Mode to Alpha Addition
            inkmode 1+64

            ; loop through the stars
            For lp=0 to Size

                    ; get th stars position
                    x#        =Stars(lp).x
                    y#        =Stars(lp).y
                    angle#=Stars(lp).Direction
                    Speed#=Stars(lp).Speed
                    
                    ; move the star 
                    x#+=sinradius(Angle#,speed#)
                    y#+=cosradius(Angle#,speed#)
                    if x#>(SCreenWidth+100)
                        ; wrap star to screen
                        x#-=(ScreenWidth+200)                                    
                        y#=rndrange(-100,ScreenHeight+100)
                        Stars(lp).speed=rndrange#(2,7)
                    endif
                    
                    ; set it's position
                    Stars(lp).x=x#
                    Stars(lp).y=y#

                    ; ugly nested loop to find near by stars
                    Glow#=10
                    For SparkLp=lp+1 to size

                                sx#=Stars(Sparklp).x
                                sy#=Stars(Sparklp).y

                                d#=getdistance2d(x#,y#,sx#,sy#)

                                if d#<120.0
                                        Glow#+=d#*(4/120.0)
                                        linec x#,y#,sx#,sy#,$102030
                                endif
                    next

                    ; draw the glow at this point
                    for GlowLP=0 to Glow#*1.2 step 4
                            circlec x#,y#,GlowLP,true,$020304            
                    next
            next


            ; draw to the screen
            rendertoscreen
            ; restore nomral inkmode
            inkmode 1
            
            ; render screen image to the screen, and clear the
            ; screen image for next update
            c=64
          BlitImageAlphaPostMultColour(Screen,0,0,RGB(c,c,c))
                    
            ; show the screen to the user                    
            sync
    loop

  Note: I'm using today's build of PlayBASIC V1.6. but this doesn't need that to function. 


  Related Examples:

      2d Stars Example

[ATLUS]

It looks very nice :)