from __future__ import division
from visual.text import *
# Bruce Sherwood, December 2007
print """
With left mouse button down,
move left or right to look around.
"""
s = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
c = len(s)
R = 5
for n in range(c):
theta = n*2*pi/c-pi/2
text(pos=(R*cos(theta), 0, R*sin(theta)),
axis=(-sin(theta), 0, cos(theta)),
string=s[n], height = 1, depth=0.5,
color=color.yellow)
camera = vector(0,0,0) # for generality; need not be at origin
# Place center of scene at a distance R from the camera:
scene.center = camera+vector(0,0,-R)
# Point the camera:
scene.forward = scene.center-camera
# scene.fov is "field of view" in radians. R times the tangent
# of half the field of view is half of the width of the scene:
scene.range = R*tan(scene.fov/2)
scene.userspin = False
down = False
lastpos = None
while 1:
rate(100)
if scene.mouse.events:
m = scene.mouse.getevent()
if m.press == 'left':
down = True
elif m.release == 'left':
down = False
if down: # and scene.mouse.pos != lastpos:
lastpos = scene.mouse.pos
lastpos.y = 0 # force mouse position to have y=0
# (lastpos-camera) is a vector parallel to screen.
# (lastpos-camera) cross norm(forward) is a vector in the +y direction,
# and this y component of the cross product is proportional to
# how far to the right the mouse is (if mouse is to left, this y
# component is negative)
rotation = cross((lastpos-camera),norm(scene.forward))
# If the mouse is to the right, y component is positive, and we need to
# turn the view toward the right, which means rotating the forward
# vector toward the right, about the +y axis, which requires a
# negative angle (vice versa if mouse is to the left, in which case
# the cross product is in the -y direction. The factor of 1/100 was
# chosen experimentally as giving an appropriate sensitivity to how
# far to the right (or left) the mouse is. Bigger mouse displacement
# makes the rotation faster.
scene.forward = scene.forward.rotate(angle=-rotation.y/100, axis=(0,1,0))
# Move the center of the scene to be a distance R from the camera,
# in the direction of forward.
scene.center = camera+R*norm(scene.forward)