N-pointed star

[bplus]

It's really radian = theta * pi / 180

and you take cos(radian) and sin(radian)

So the numbers are right but your words are misleading.

BTW QB64 has _Pi though uglier than just Pi you don't need the Pi = 3.14... line either.

Here is much more versatile routine with any inner and outer radius for star, any number of points, and color and you can fill it or not, demo of sub Star

This requires you to set color before calling Star to draw it.

Code: (Select All)

Sub Star (x, y, rInner, rOuter, nPoints, angleOffset, TFfill)
    ' x, y are same as for circle,
    ' rInner is center circle radius
    ' rOuter is the outer most point of star
    ' nPoints is the number of points,
    ' angleOffset = angle offset IN DEGREES, it will be converted to radians in sub
    ' this is to allow us to spin the polygon of n sides
    ' TFfill filled True or False (1 or 0)
    p_angle = Radians * (360 / nPoints): rad_angle_offset = Radians * angleOffset
    x1 = x + rInner * Cos(rad_angle_offset)
    y1 = y + rInner * Sin(rad_angle_offset)
    For i = 0 To nPoints - 1
        x2 = x + rOuter * Cos(i * p_angle + rad_angle_offset + .5 * p_angle)
        y2 = y + rOuter * Sin(i * p_angle + rad_angle_offset + .5 * p_angle)
        x3 = x + rInner * Cos((i + 1) * p_angle + rad_angle_offset)
        y3 = y + rInner * Sin((i + 1) * p_angle + rad_angle_offset)
        Line (x1, y1)-(x2, y2)
        Line (x2, y2)-(x3, y3)
        x1 = x3: y1 = y3
    Next
    If TFfill Then
        'Circle (x, y), 2, &HFFFFFFFF
        Paint (x, y), _DefaultColor, _DefaultColor
    End If
End Sub

Demo

Code: (Select All)

_Title "Even Better Stars" 'b+ 2021-11-18 trans of
'Better Stars.sdlbas (B+=MGA) 2016-05-16
' odd or even number of point, fat or skinny, better fills

Const Pi = _Acos(-1) 'cute way to get pi
'Print (Pi) 'check pi
'End
Const Radians = Pi / 180 'to convert an angle measured in degrees to and angle measure in radians, just mutiply by this
Const Xmax = 700
Const Ymax = 700
Const Cx = Xmax / 2
Const Cy = Ymax / 2

'setdisplay(xmax, ymax, 32, 1)
Screen _NewImage(Xmax, Ymax, 32)
_ScreenMove 300, 40
'setcaption("Better Stars demo")
'autoback(-2)

'main
Const NS = 100
Dim Shared x(NS), y(NS), dx(NS), dy(NS), ri(NS), ro(NS), p(NS), a(NS), turn(NS), fill(NS), c(NS) As _Unsigned Long
loopcounter = 0
For i = 0 To NS
    NewStar i
Next
While _KeyDown(27) = 0
    Line (0, 0)-(Xmax, Ymax), _RGB32(0, 0, 0, 30), BF
    For i = 0 To NS
        If x(i) > 0 And x(i) < Xmax And y(i) > 0 And y(i) < Ymax Then
            'ink(colr(c(i)))
            Color c(i)
            Star x(i), y(i), ri(i), ro(i), p(i), a(i), fill(i)
            x(i) = x(i) + dx(i)
            y(i) = y(i) + dy(i)
            ri(i) = 1.015 * ri(i)
            ro(i) = 1.015 * ro(i)
            a(i) = a(i) + turn(i)
        Else
            NewStar i
        End If
    Next
    'screenswap
    _Display
    _Limit 100
    'wait(50)
    loopcounter = loopcounter + 1
Wend


Sub NewStar (nxt)
    angle = Rnd * 2 * Pi
    r = Rnd * 6 + 1
    dx(nxt) = r * Cos(angle)
    dy(nxt) = r * Sin(angle)
    r = Rnd * 300
    x(nxt) = Cx + r * dx(nxt)
    y(nxt) = Cy + r * dy(nxt)
    ri(nxt) = Rnd
    ro(nxt) = ri(nxt) + 1 + Rnd
    p(nxt) = 3 + Int(Rnd * 9)
    a(nxt) = Rnd * 2 * Pi
    turn(nxt) = Rnd * 6 - 3
    fill(nxt) = Int(Rnd * 2)
    c(nxt) = rndColor~&
End Sub

Function rndColor~& ()
    rndColor~& = _RGB32(Rnd * 255, Rnd * 255, Rnd * 255)
End Function

Sub Star (x, y, rInner, rOuter, nPoints, angleOffset, TFfill)
    ' x, y are same as for circle,
    ' rInner is center circle radius
    ' rOuter is the outer most point of star
    ' nPoints is the number of points,
    ' angleOffset = angle offset IN DEGREES, it will be converted to radians in sub
    ' this is to allow us to spin the polygon of n sides
    ' TFfill filled True or False (1 or 0)
    p_angle = Radians * (360 / nPoints): rad_angle_offset = Radians * angleOffset
    x1 = x + rInner * Cos(rad_angle_offset)
    y1 = y + rInner * Sin(rad_angle_offset)
    For i = 0 To nPoints - 1
        x2 = x + rOuter * Cos(i * p_angle + rad_angle_offset + .5 * p_angle)
        y2 = y + rOuter * Sin(i * p_angle + rad_angle_offset + .5 * p_angle)
        x3 = x + rInner * Cos((i + 1) * p_angle + rad_angle_offset)
        y3 = y + rInner * Sin((i + 1) * p_angle + rad_angle_offset)
        Line (x1, y1)-(x2, y2)
        Line (x2, y2)-(x3, y3)
        x1 = x3: y1 = y3
    Next
    If TFfill Then
        'Circle (x, y), 2, &HFFFFFFFF
        Paint (x, y), _DefaultColor, _DefaultColor
    End If
End Sub

Oh ha! I was using my own way to get Pi not using _Pi either

Oh and this was before using _D2R(degrees) ie radians = _D2R(degrees) and the reverse of course is degrees = _R2D(radians) so we used Pi/180 or 180/Pi to convert degrees to radians or vice versa.