Rotation an object around his center using vpython

Question

I'm making a moonlander game using VPython. The moonlander itself must be able to rotate around his own center, but he rotates around the wrong axis and/or around his original position instead. The axis and position where it has to rotate around don't change when the position of the moonlander changes. I don't know how to do this.

The moonlander is made of curves, but I have a frame that contains the moonlander. Here is the code (sorry about the code being in dutch, I hope you understand enough):

from visual import *
from math import *
from random import randint
maanoppervlak = curve(pos=[(-20,-2),(-18,-5)],color=color.red)
maanoppervlak.append(pos=(-18,-5))
maanoppervlak.append(pos=(-15,-4),color=color.red)
maanoppervlak.append(pos=(-15,-4))
maanoppervlak.append(pos=(-14,-4),color=color.red)
maanoppervlak.append(pos=(-14,-4))
maanoppervlak.append(pos=(-13,-15),color=color.red)
maanoppervlak.append(pos=(-13,-15), color=color.green)
maanoppervlak.append(pos=(-7,-15),color=color.green)
maanoppervlak.append(pos=(-7,-15),color=color.red)
maanoppervlak.append(pos=(-3,4),color=color.red)
maanoppervlak.append(pos=(-3,4))
maanoppervlak.append(pos=(-1,0),color=color.red)
maanoppervlak.append(pos=(-1,0))
maanoppervlak.append(pos=(3,-2),color=color.red)
maanoppervlak.append(pos=(3,-2),color=color.green)
maanoppervlak.append(pos=(8,-2),color=color.green)
maanoppervlak.append(pos=(8,-2),color=color.red)
maanoppervlak.append(pos=(13,-8),color=color.red)
maanoppervlak.append(pos=(13,-8))
maanoppervlak.append(pos=(16,-5),color=color.red)
maanoppervlak.append(pos=(16,-5))
maanoppervlak.append(pos=(19,-12),color=color.red)
maanoppervlak.append(pos=(19,-12))
maanoppervlak.append(pos=(20,-7), color=color.red)

print scene.width

f = frame() #maken van een frame waar de maanlander in zit
f.axis = (1,0,0)
f.pos = vector(-4,-10,0)
maanlander = curve(frame=f, pos=[(1,1),(2,1),(1.5,1),(1.5,2),(2,2.5),(2,3.5),(2.75,3.5),
(2.25,4),(2.25,4.5),(2.75,5),(3.75,5),(4.25,4.5),
(4.25,4),(3.75,3.5),(4.5,3.5),(4.5,2.5),(3.5,2.5),(3.75,2),
(2.75,2),(3,2.5),(2,2.5),(4.5,2.5),(5,2),(5,1),(4.5,1),
(5.5,1)],color=color.blue)
maanlander.accel = vector(0,0) #acceleratie van de maanlander
f.accel = vector(0,0) #acceleratie van de frame (deze of die hierboven is waarschijnlijk overbodig)
f.velocity = vector(0,0) #snelheid van de frame
deltat = 0.005
state = true
while state == true: #start van de loop
    rate(100)
    f.velocity = f.velocity + maanlander.accel*deltat #bepaalt de snelheid adhv de accel.
    maanlander.pos = maanlander.pos + f.velocity*deltat #bepaalt de positie adhv de snelheid
    if scene.kb.keys: # is there an event waiting to be processed?
            s = scene.kb.getkey() # obtain keyboard information
            if s == 'left': #er wordt op linkertoets gedrukt
                f.rotate(angle=pi/15., axis=(0,0,1), origin=(f.pos + vector(2.75,2.5,0))) #object moet rond zijn middden draaien (werkt nog niet)
            elif s == 'right':
                f.rotate(angle=-pi/15., axis=(0,0,1), origin=vector(2.75,2.5,0)) #zelfde als bij left, maar in omgekeerde richting
            elif s == 'up': #'boost'
                maanlander.accel = maanlander.accel + vector(0,10)

So, how can you rotate the moonlander, and also when it has a different position than its original one?

Thanks in advance

Answer 1

伊格纳西奥（Ignacio）说将月球着陆器转换为原点（ center ），然后围绕center旋转所有物体，然后再将其转换回原来的位置。