locate a certain point in the scene 3D

[Johannes]

Well, maybe I'm just not good enough to pick a point on the line (because the line is so small....).
I just want to use this to get the position of a certain point in the scene...

def mouseclick(button):
	global beginPos0502, line0503
	pos = viz.mousepos()
	print 'mouse is currently at',pos
	if button == viz.MOUSEBUTTON_RIGHT:
		line = viz.screentoworld(viz.mousepos())
		begin = line[:3]
		end = line[3:]
		viz.startlayer(viz.LINE_LOOP)
		viz.vertex(begin)
		viz.vertex(end)
		line0503 = viz.endlayer()
		print end
	if button == viz.MOUSEBUTTON_LEFT:
		object = viz.pick()
		#if object.valid() and object != arrow:
		if (object.valid() and object ==airtrack.slider):
			pos = object.get(viz.POSITION)
			beginPos0502=pos[0]
			viz.mousedata(viz.ABSOLUTE,viz.ABSOLUTE)
			viz.callback(viz.MOUSEMOVE_EVENT, mymousemove)
			viz.mouse(viz.OFF)
	if button == viz.MOUSEBUTTON_MIDDLE:
		print 'middle'
		object = viz.pick()
		if (object.valid()and object ==line0503):
			print object.get(viz.POSITION)