Drawing 20 planets with graphical commands

[bplus]

How to draw a ring around a planet with just QB64. Basically draw the back half of the ellipse ring draw the planet then draw the front half of the ellipse ring.

Code: (Select All)

Option _Explicit



_Title "Arc of Ellisps" 'b+ 2021-12-25



Dim sw, sh

sw = 600: sh = 600



Screen _NewImage(sw, sh, 32)

_ScreenMove 300, 200



ArcRingOfEllipse sw / 2, sh / 2, 120, 200, _Pi(0), _Pi(1), .25, &HFFAAAAFF

Ring sw / 2, sh / 2, 0, 85, &HFF880088

ArcRingOfEllipse sw / 2, sh / 2, 120, 200, _Pi(1), _Pi(1.999), .25, &HFFAAAAFF



Sub Ring (cx, cy, innerRadius, outerRadius, colr~&) ' wont work well with alpha's < 255

    Dim r

    For r = innerRadius To outerRadius Step .25

        Circle (cx, cy), r, colr~&

    Next

End Sub



'ra's here go Counter Clockwise from East

Sub ArcRing (cx, cy, innerRadius, outerRadius, raStart, raEnd, colr~&) ' ra's 0 to <2*pi (almost)

    Dim r

    For r = innerRadius To outerRadius Step .25

        Circle (cx, cy), r, colr~&, raStart, raEnd

    Next

End Sub



'ra's here go Counter Clockwise from East

Sub ArcRingOfEllipse (cx, cy, innerRadius, outerRadius, raStart, raEnd, aspect, colr~&) ' ra's 0 to <2*pi (almost)

    Dim r

    For r = innerRadius To outerRadius Step .25

        Circle (cx, cy), r, colr~&, raStart, raEnd, aspect

    Next

End Sub

If you are not familiar with Radians: to convert Degrees to Radians (ra = radian angle 0 to _Pi(2)) use D2R() function. Radians are just another scale system for angle measures and used for all trig functions as opposed to Degrees.

If you want to draw ellipse rings that are transparent, Steve's recent Ellipse.Arc.Ring stuff might work because he is using scan lines that dont overlap. That's what you need for transparencies without overlap (no stripes and you can see whats under the drawing). https://qb64phoenix.com/forum/showthread...1#pid34131

As OldMoses mentioned, you can tilt the ellipsii with Rotozoom (after putting the image like above into a contianer with an image handle eg Image below) x,y is your planet center, scale just use 1 for no shrink nor expanding and degreesRotation the angle to shift the ellipse to. 

Code: (Select All)

Sub RotoZoom (X As Long, Y As Long, Image As Long, Scale As Single, degreesRotation As Single)
    Dim px(3) As Single, py(3) As Single, W&, H&, sinr!, cosr!, i&, x2&, y2&
    W& = _Width(Image&): H& = _Height(Image&)
    px(0) = -W& / 2: py(0) = -H& / 2: px(1) = -W& / 2: py(1) = H& / 2
    px(2) = W& / 2: py(2) = H& / 2: px(3) = W& / 2: py(3) = -H& / 2
    sinr! = Sin(-degreesRotation / 57.2957795131): cosr! = Cos(-degreesRotation / 57.2957795131)
    For i& = 0 To 3
        x2& = (px(i&) * cosr! + sinr! * py(i&)) * Scale + X: y2& = (py(i&) * cosr! - px(i&) * sinr!) * Scale + Y
        px(i&) = x2&: py(i&) = y2&
    Next
    _MapTriangle (0, 0)-(0, H& - 1)-(W& - 1, H& - 1), Image& To(px(0), py(0))-(px(1), py(1))-(px(2), py(2))
    _MapTriangle (0, 0)-(W& - 1, 0)-(W& - 1, H& - 1), Image& To(px(0), py(0))-(px(3), py(3))-(px(2), py(2))
End Sub