def __init__(self, cx, cy, radius):
"""
Initialize instance of ArcBall with no constraint on axis of rotation
"""
self.center_x = cx
self.center_y = cy
self.radius = radius
self.v_down = PVector()
self.v_drag = PVector()
self.q_now = Quaternion()
self.q_down = Quaternion()
self.q_drag = Quaternion()
self.axis_set = [
PVector(1.0, 0.0, 0.0),
PVector(0.0, 1.0, 0.0),
PVector(0.0, 0.0, 1.0)
]
self.axis = -1
def __mouse2sphere(self, x, y):
"""
private map mouse to ArcBall (sphere)
"""
v = PVector()
v.x = (x - self.center_x) / self.radius
v.y = (y - self.center_y) / self.radius
mag = v.x * v.x + v.y * v.y
if (mag > 1.0):
v.normalize()
else:
v.z = sqrt(1.0 - mag)
if (self.axis != -1):
v = self.__constrain(v, self.axis_set[self.axis])
return v
