# Nimmt die Bezierkurven aus myspline und erzeugt 
# die Bahn und die Kamera-Animation

# Import in Blender 2.8 (see https://devtalk.blender.org/t/2-80-using-multiple-internal-scripts-breaking-change/6980 )
Bezier = bpy.data.texts["bezier.py"].as_module().Bezier

obj = bpy.data.objects['mySpline']

# Kurvenpunkte auslesen
mypoints=[]
if obj.type == 'CURVE':
    for subcurve in obj.data.splines:
        curvetype = subcurve.type
        if curvetype == 'BEZIER':
            for bezpoint in subcurve.bezier_points:
                mypoints.append(bezpoint.handle_left)
                mypoints.append(bezpoint.co)
                mypoints.append(bezpoint.handle_right)
                

# Sammlung von Bezierkurven erzeugen
mySplines = []
numpoints = len(mypoints)
totalLength = 0
for i in range(numpoints//3):
    mySplines.append(Bezier((mypoints[i*3+1],
        mypoints[i*3+2], 
        mypoints[(i*3+3)%numpoints], 
        mypoints[(i*3+4)%numpoints])))
    totalLength+=mySplines[-1].length()


# Bahn erzeugen
try:
    bpy.ops.collection.objects_remove(bpy.data.collections['Rails'])
except:
    pass
    
railsCol = bpy.data.collections.new('Rails')
linksCol = bpy.data.collections.new('RailLinks')
railsCol.children.link(linksCol)
bpy.context.scene.collection.children.link(railsCol)
               
abstand = 0.2  # Bahnpunkte
ldone = 0  # Erledigte Bahnstrecke
i=0  # Aktuelle Bezierkurve
t = 0 # Aktuelle t-Parameter
g = Vector(0,0,-9.81) # Gravitationbeschleunigung
hmax = 40  # Hoehe fuer v=0
# Bahnpunkte: Ctrl-Links, Knoten, Ctrl-Rechts
railspts=[[],[],[]]  # Bahnpunkte, Schiene L, Schiene R, Träger 
while(ldone<totalLength):
    dl = abstand;
    tnext = -1
    while(tnext<0):
        tnext = mySplines[i].forward(dl, t)
        if (tnext<0) : # We get the negative remaining length
            i=(i+1)%numSplines
            t = 0
            dl=abs(tnext)
        else:
            ldone+=dl
    t = tnext
    # Potentielle Energie mgh
    ekin = (hmax-mySplines[i].x(t).z)*abs(g.z)
    # Ek = 1/2 * m * v^2
    v = (2*ekin)**0.5
    # Koordinatensystem (vorne, oben, rechts)
    k = mySplines[i].koordsyst(t,v,g)
    # Bahnpunkte berechnen
    #
    #
    #
    


# Blender-Kurven aus den Bahnpunkten erzeugen
for j in range(3):
    curvedata = bpy.data.curves.new(name="rail"+str(j), type='CURVE')
    curvedata.dimensions = '3D'
    objectdata = bpy.data.objects.new("rail"+str(j), curvedata)    
    objectdata.location = (0,0,0)
    objectdata.data.bevel_depth = 0.01

    railsCol.objects.link(objectdata)
 
    polyline = curvedata.splines.new('BEZIER')    
    polyline.bezier_points.add(len(railspts[j])-1)    
 
    for idx, (h1, knot, h2) in enumerate(railspts[j]):
        point = polyline.bezier_points[idx]
        point.co = knot
        point.handle_left = h1
        point.handle_right = h2
        point.handle_left_type = 'ALIGNED'
        point.handle_right_type = 'ALIGNED'