basic256/Examples/Demo/FieldLines.kbs at v2.3.1 · uglymike17/basic256 · GitHub

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# Field Lines
#********************************
# Lacking inspiration, I shamelessly pulled this code from a Facebook post by John Penner with QB64 code and ported it to Basic256
# Apparently inspired by cool demos done by Kurt Moerman and Eric Schraf (FB group 'BASIC Programming Language')
# Moved color cycling outside the points loop, sped up the rotation a bit and added some alpha... Pretty happy with the result
# Play with nbr_lines and nbr_points for changing the look
#Setup
  gosub ScreenSetup
  gosub ParameterSetting
#Draw
  while 1
    gosub Draw
  end while

# Subroutines
#****************************
ScreenSetup:
  Fastgraphics
  width=900
  height=600
  graphsize width,height
  color black
  rect(0,0,width-1,height-1)
  refresh
return


ParameterSetting:
  aspect_ratio = width/height
  nbr_lines = 250
  nbr_points = 20 # increase this if you want it 'hairy'
  StepSize= 0.02
  RotationStep = 0.030
  heading = 4 * pi / 3
return

Draw:
    seed 1
    color rgb(0,0,0,30)
    rect(0,0,width,height)
    refresh
    For lines = 0 To nbr_lines
        x = 1.5 * Rand - 0.75
        y = 1.5 * Rand - 0.75
        old_x = x
        old_y = y
		col_green = 127 + 127 * sin(nbr_points / 4 + heading)
		color rgb(255, col_green, 0)
        For points = 0 To nbr_points
            angle = atan2(y, x) + heading + Sin(6 * pi * sqr(x*x+y*y)) / 4
            x = x + StepSize* Cos(angle)
            y = y + StepSize* Sin(angle)
            Line (width/2 + old_x * (width/3),height/2 - old_y * (height/2),width/2  + x * (width/3),height/2 - y * (height/2))
			old_x=x
			old_y=y
        Next points
    Next lines
    heading = heading + RotationStep
    If heading > 10 * pi / 3 Then heading = 4 * pi / 3
    refresh
return

#Functions
#****************************
function atan2(y, x)
    if x > 0 then return atan(y / x)
    if x < 0 and y >= 0 then return atan(y / x) + pi
    if x < 0 and y < 0 then return atan(y / x) - pi
    if x = 0 and y > 0 then return pi / 2
    if x = 0 and y < 0 then return -pi / 2
    return 0
end function