Angle Collisions

[james2464]

Well I finally got something that works, although it's just a single reflection.  But I finally clued in on what the dot product is used for, and then it was a matter of completing the calculations to the reflection point.

So this is a utility program, using both the mouse to locate the ball and arrow keys to rotate the angled wall.

Code: (Select All)

'vector reflection demo
'james2464

Screen _NewImage(800, 600, 32)

Const PI = 3.141592654#

Dim Shared x, y, h, dx, dy, nx, ny, na As Single


Dim 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)


'0,0 origin
xx = 400
yy = 300

Line (0, yy)-(800, yy), c(0)
Line (xx, 0)-(xx, 600), c(0)


x = 70: y = 90 'ball position
na = 60 'reflecting surface angle

flag = 0
Do

    _Limit 10
    Cls

    'chip starting pos - using mouse
    mouseclick1 = 0


    Do While _MouseInput
    Loop
    mx% = _MouseX
    my% = _MouseY
    If mx% < xx - 400 Then mx% = xx - 400
    If mx% > xx + 400 Then mx% = xx + 400
    If my% < yy - 300 Then my% = yy - 300
    If my% > yy + 300 Then my% = yy + 300
    lc% = _MouseButton(1)
    If lc% = -1 Then mouseclick1 = 1

    x = 0 - xx + mx%
    y = yy - my%

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


    'Locate 3, 1
    'Print "Calculations"

    'Print "Motion vector I ("; -x; ","; y; ")"
    h = _Hypot(-x, y)
    'Print h; "(hypot)"
    'Print

    nx = Sin(na * (PI / 180))
    ny = Cos(na * (PI / 180))

    'Print "Normal X:"; nx
    'Print "Normal Y:"; ny
    'Print
    'Print "Dot product to find N length"
    dx = -x * nx * -1: dy = y * ny
    'Print dx; dy
    'Print
    ndp = dx + dy
    'Print "N length (distance from origin to line A"
    'Print ndp
    'Print
    ard = Sqr(h ^ 2 - ndp ^ 2)
    'Print "Distance from N-A to R"
    'Print ard
    'Print "Point R location"
    'Print nx * ard; ny * ard
    'Print nx * ndp; ny * ndp
    w2x = ny * ard: w2y = nx * ard
    u2x = nx * ndp: u2y = ny * ndp
    rx = w2x + u2x: ry = w2y - u2y
    Circle (xx + rx, yy + ry), 10, c(3) 'point R
    Line (xx, yy)-(xx + rx, yy + ry), c(3) 'line from origin to point R

    'reflecting surface
    A = (Sin(na * (PI / 180))) * 200
    B = (Cos(na * (PI / 180))) * 200
    Line (xx, yy)-(xx + B, yy + A), c(1)
    Line (xx, yy)-(xx - B, yy - A), c(1)


    Circle (xx + x, yy - y), 10, c(2) 'point I
    Line (xx, yy)-(xx + x, yy - y), c(2)


    Locate 1, 1
    Print "Vector Reflection"
    Print "Use up and down arrow keys to rotate wall"
    Locate 35, 1
    Print "Wall angle:"; na

    Locate 1, 70
    Print "I ="; x; ","; y;

    Locate 35, 70
    Print "R ="; Int(rx); ","; Int(-ry)


    change_angle1 = uparrowkey
    change_angle2 = downarrowkey

    _Display

Loop Until flag = 1





Function uparrowkey
    uparrowkey = 0
    If _KeyDown(18432) Then '                                 IF up arrow key was pressed
        na = na + 1. '                                        increase reflection angle
        uparrowkey = 1 '                                      record that this happened
    End If
End Function


Function downarrowkey
    downarrowkey = 0
    If _KeyDown(20480) Then '                                 IF down arrow key was pressed
        na = na - 1. '                                        decrease reflection angle
        downarrowkey = 1 '                                    record that this happened
    End If
End Function