def projectToTrackball(self, camera, newX, newY):
""" Project the mouseposition onto a trackball to rotate the camera.
Parameters:
newX - new x position on the trackball
newY - new y position on the trackball
Return:
vector - position on the trackball
"""
x = newX / (camera.getWindowWidth() / 2.0)
y = newY / (camera.getWindowHeight() / 2.0)
x = x - 1
y = 1 - y
z2 = 1 - (x * x + y * y)
z = 0.0
if z2 > 0:
z = math.sqrt(z2)
# print " x, y, z on sphere: " , x, y, z
p = Vec([x, y, z])
p.normalize()
return p
