[Visualpython-users] Moving the camera under program control

[Jeremy F. <Jer...@lo...>]

Hello !

I've got few questions about vpython.

I'm trying to build a little environnement in which i can control the camera 
with a program. Below that message is the code i wrote. This is largely 
inspired from stonehenge.py and display_kernel as advised on the list. It's 
working ... (i think) but i'm wondering if i'm doing it in the right way .... 
especially the things  like   :

old = scene.range [....] scene.range=old    .. i don't really understand what 
i'm doing there

and

using scene.up to compute the orth vector = norm(cross(forward,up)).  I 
thought the up vector was fixed .... to compute the orth vector that 
corresponds to a local horizontal axis for the camera, i should use a local 
up axis ... moving as i move my camera ?! am i wrong ?


What do you think about it ?

Thanks  !

Jeremy.


#!/usr/bin/env python

from visual import *

cylinder()

def rotate_camera(pan,tilt):
    old = scene.range
    newforward = rotate(scene.forward,axis=scene.up,angle=pan)
    scene.center = 
scene.mouse.camera+newforward*mag(scene.center-scene.mouse.camera)
    scene.forward = newforward
    scene.range = old
    orth = norm(cross( scene.forward,scene.up))
    newforward = rotate(scene.forward,axis = orth,angle=tilt)
    scene.center = 
scene.mouse.camera+newforward*mag(scene.center-scene.mouse.camera)
    scene.forward = newforward
    scene.range = old
   
while 1:
    # The camera is moved with the mouse and up,down,left,right keys
    if scene.kb.keys: # is there an event waiting to be processed?
        s = scene.kb.getkey() # obtain keyboard information
        if(s == 'up'):
            rotate_camera(0,0.1)
        elif(s=='down'):
            rotate_camera(0,-0.1)
        elif(s=='left'):
            rotate_camera(0.1,0)
        elif(s=='right'):
            rotate_camera(-0.1,0)