WorldViz User Forum - constant speed on animation path

Hello, By pressing 'a', my script simply starts a car in a road. My question is how to make the car move in a constant speed. I use path.constantspeed(), but seems to me that the car will accelerate when it move along the circle. Does the way I add control point have problem?

Code:

import viz

import math

import time



viz.go()





myroad = viz.add('road4.wrl')

myroad.setPosition(0,0.1,0)

myroad.setScale(3.2,3.2,3.2)



mymini = viz.add('mini.osgx')

mymini.setPosition(-10,-10,0)



y_pos_car = 0.14

path = viz.addAnimationPath()

positions = [ [2,y_pos_car,50], [1,y_pos_car,35], [0,y_pos_car,25], [-1,y_pos_car,15], 

                                [-1,y_pos_car,8], [-25,y_pos_car,0], [-15,y_pos_car,-8], [-10,y_pos_car,-10], 

                                [-6,y_pos_car,-10], [-3,y_pos_car,-12], [0,y_pos_car,-18], [3,y_pos_car,-17], 

                                [6,y_pos_car,0], [10,y_pos_car,4], [15,y_pos_car,2], [25,y_pos_car,-8], 

                                [35,y_pos_car,-16], [50,y_pos_car,-10], [60,y_pos_car,20], [80,y_pos_car,40],

                                [200,y_pos_car,200] ]

for x in range(0,len(positions)):

        cp = viz.add(viz.CONTROL_POINT)

        cp.setPosition(positions[x])

        path.add(cp,x+1)



path.loop(viz.OFF)

path.translatemode(viz.BEZIER)

path.setAutoRotate(viz.ON)

mymini.link(path)



        

def mytimer(num):

        pass



def onkeydown(key):

        if key == 'a': 

                path.play()

                path.constantspeed(viz.ON,6.7)

                





viz.callback(viz.KEYBOARD_EVENT, onkeydown) #keyboard event callback

viz.callback(viz.TIMER_EVENT, mytimer) #timer event callback

viz.starttimer(0,1/60,viz.FOREVER) #timer

BTW, I cannot attach my models zip file here because it always said "Upload of file failed". What should I try?

Thanks a lot!