Angle Collisions

[james2464]

Making some progress.   I worked out the line endpoint collisions, and I'm in the process of sorting out the side collisions.  Some things don't quite add up.  The endpoints work really well - when rotating the line with the mouse wheel,  you can kind of make the ball go where you want.

Code: (Select All)

'vector reflection and line detection demo
'james2464

Dim Shared scx, scy As Integer
scx = 800: scy = 600
Screen _NewImage(scx, scy, 32)

Const PI = 3.141592654#

Dim Shared x, y, h, xv, yv, ndpx, ndpy, rx, ry
Dim Shared cpa, cpb, a, b, a2, b2, xx, yy

Dim Shared c(10) As Long
c(0) = _RGB(30, 30, 30)
c(1) = _RGB(255, 255, 255)
c(2) = _RGB(255, 255, 0)
c(3) = _RGB(255, 0, 0)
c(4) = _RGB(0, 255, 0)
c(5) = _RGB(0, 255, 255)
c(6) = _RGB(255, 0, 255)

'location of wall center point
xx = 400
yy = 300
na = 45 'wall starting angle (mouse wheel controlled)
wlen = 150 'wall length - each half
ballrad = 40 'ball radius

xv = 1.5 'ball x velocity
yv = -3.5 'ball y velocity
sbx = 200 'starting x position
sby = 200 'starting y position

flag = 0
message = 0
Do

    _Limit 50
    Cls

    '=====================================================
    mouseclick1 = 0
    _MouseHide
    Do While _MouseInput
        na = na + _MouseWheel * 2
    Loop
    mx% = _MouseX
    my% = _MouseY
    If mx% < 0 Then mx% = 0
    If mx% > scx Then mx% = scx
    If my% < 0 Then my% = 0
    If my% > scy Then my% = scy
    lc% = _MouseButton(1)
    rc% = _MouseButton(2)
    If lc% = -1 Then mouseclick1 = 1
    If rc% = -1 Then mouseclick2 = 1

    'sbx = mx%: sby = my% 'ball controlled by mouse
    sbx = sbx + xv
    sby = sby + yv
    If sbx > (scx - ballrad) Then
        xv = xv * -1
        t = sbx - (scx - ballrad)
        sbx = sbx - t
    End If
    If sby > (scy - ballrad) Then
        yv = yv * -1
        t = sby - (scy - ballrad)
        sby = sby - t
    End If
    If sbx < ballrad Then
        xv = xv * -1
        t = ballrad - sbx
        sbx = sbx + t
    End If
    If sby < ballrad Then
        yv = yv * -1
        t = ballrad - sby
        sby = sby + t
    End If


    '=====================================================
    'origin lines
    'Line (0, yy)-(800, yy), c(0)
    'Line (xx, 0)-(xx, 600), c(0)

    '=====================================================
    Circle (sbx, sby), (ballrad - 1), c(2) 'screen location of ball
    x = sbx - xx: y = 0 - sby + yy 'location relative to wall
    'Locate 1, 1
    'Print na, x, y
    h = (_Hypot(-x, y))

    '=====================================================
    nx = Cos(na * (PI / 180)) 'normalize wall angle
    ny = Sin(na * (PI / 180)) 'normalize wall angle

    dx = -x * ny * -1: dy = y * nx: ndp = dx + dy
    'dot product V.N - used to find distance of N
    'The distance of N is from the point of collision to the middle of line A
    'line A is a line from point I to point R (parallel to the angled wall)

    ndpx = Sin(na * (PI / 180)) * ndp
    ndpy = Cos(na * (PI / 180)) * ndp


    sidecollisionpoint



    '=====================================================
    'angled wall
    a = (Sin(na * .017453292)) * wlen
    b = (Cos(na * .017453292)) * wlen
    a2 = a * -1: b2 = b * -1


    c(9) = c(1)

    'find length of line A
    segx = Abs(x - rx)
    segy = Abs((yy - y) - (yy + ry))
    sega = _Hypot(segx, segy)

    'find distance from point I to wall endpoints
    i2w1x = Abs(x - b)
    i2w1y = Abs(a + y)
    i2w2x = Abs(x + b)
    i2w2y = Abs(y - a)

    i2wh1 = _Hypot(i2w1x, i2w1y)
    i2wh2 = _Hypot(i2w2x, i2w2y)

    If i2wh1 < i2wh2 Then 'determine which end the ball is closer to
        i2ws = 1: i2w = i2wh1
    Else
        i2ws = 2: i2w = i2wh2
    End If

    If sega < (wlen * 2) Then
        If Abs(ndp) <= ballrad Then '                                          *****  collision with side of the line  *****
            c(9) = c(3) 'if beside the wall, just check length of line N
            collisionpointa = (Sin(na * .017453292)) * (sega / 2)
            collisionpointb = (Cos(na * .017453292)) * (sega / 2)
            If i2ws = 1 Then
                cpa = yy + collisionpointa: cpb = xx + collisionpointb
            End If
            If i2ws = 2 Then
                cpa = yy - collisionpointa: cpb = xx - collisionpointb
            End If
            Locate 3, 1
            Print "                      i2ws"; i2ws
            Circle (cpb, cpa), 5, c(4) 'circle the collision point
            sidecollisionvector
        End If
    Else
        If i2w <= ballrad Then '                                              *****  collision with endpoint of the line  *****
            c(9) = c(3)

            If i2ws = 1 Then
                cpa = yy - a2: cpb = xx + b
                endpointcollision1
            End If

            If i2ws = 2 Then
                cpa = yy - a: cpb = xx + b2
                endpointcollision2
            End If

            Circle (cpb, cpa), 5, c(4) 'circle the collision point
        End If
    End If

    '==========================================================================================


    Line (xx, yy)-(xx + b, yy + a), c(9) 'angled wall (collision with ball changes colour)
    Line (xx, yy)-(xx - b, yy - a), c(9) 'angled wall (collision with ball changes colour)


    If mouseclick1 = 1 Then 'show geometry lines
        If sega <= (wlen * 2) Then
            Line (cpb, cpa)-(cpb - xv * 80, cpa - yv * 80), c(2) 'collision to point I
            'Line (cpb + x, cpa - y)-(cpb + rx, cpa + ry), c(4) 'line A
            Line (cpb, cpa)-(cpb + rx, cpa + ry), c(3) 'collision to point R

            Line (cpb, cpa)-(cpb + ndpx, cpa - ndpy), c(5) 'line N
        End If
        If sega > (wlen * 2) Then
            If i2ws = 1 Then
                Line (xx + x, yy - y)-(xx + b, yy + a), c(6) 'endpoint collision line
            End If
            If i2ws = 2 Then
                Line (xx + x, yy - y)-(xx - b, yy - a), c(6) 'endpoint collision line
            End If
        End If
        message = 1
    End If


    If message = 0 Then
        Locate 1, 1
        Print "Left click to show lines"
        Print "Scroll mouse wheel to rotate"
    End If

    _Display
    If mouseclick2 = 1 Then flag = 1

Loop Until flag = 1


Sub sidecollisionpoint
    'calculate point R
    th1 = _Atan2(-y, x) 'radian value of ball (point I)
    'th1 = _Atan2(-yv, xv)
    th2 = _Atan2(-ndpy, ndpx) 'radian value of line N
    thd = th1 - th2 'find difference
    th3 = th2 - thd 'subtract difference from line N
    rx = Cos(th3) * h: ry = Sin(th3) * h 'point R position - th3 * length of point I to collision point
End Sub


Sub sidecollisionvector
    tx = xv: ty = yv: th = _Hypot(tx, ty)
    tx2 = tx / th: ty2 = ty / th
    spd = _Hypot(tx, ty) 'speed of existing motion vector
    th1 = _Atan2(tx, -ty) 'radian value of motion vector
    th2 = _Atan2(-ndpy, ndpx) 'radian value of line N
    thd = th1 - th2 'find difference
    th3 = th2 - thd 'subtract difference from line N
    newxv = Cos(th3): newyv = Sin(th3)
    xv = newxv * spd: yv = newyv * spd * -1
End Sub

Sub endpointcollision1
    tx = x - b: ty = y - a2: th = _Hypot(tx, ty)
    tx2 = tx / th: ty2 = ty / th
    txv = Abs(xv): tyv = Abs(yv): spd = _Hypot(txv, tyv)
    xv = tx2 * spd: yv = ty2 * spd * -1
End Sub


Sub endpointcollision2
    tx = x - b2: ty = y - a: th = _Hypot(tx, ty)
    tx2 = tx / th: ty2 = ty / th
    txv = Abs(xv): tyv = Abs(yv): spd = _Hypot(txv, tyv)
    xv = tx2 * spd: yv = ty2 * spd * -1
End Sub