printer.py 文件源码

def get_xy(alpha, beta, structure_settings):

    r = structure_settings.r  # short arm length (attached to the rotative axis)
    a = structure_settings.a  # long arm length
    s = structure_settings.s  # pen distance

    xa = structure_settings.xa #left short arm x
    xb = structure_settings.xb #right short arm x


    # d is the first short arm extremity
    xd = xa - r * math.sin(alpha)
    yd = r * math.cos(alpha)

    # e is the first short arm extremity
    xe = xb - r * math.sin(beta)
    ye = r * math.cos(beta)

    de = compute_distance(xd, yd, xe, ye)

    #theta is the angle formed by de and the left long arm
    cos_theta = de/float(2 * a)
    cos_theta = min(cos_theta, 1.0)
    cos_theta = max(cos_theta, -1.0)
    theta = math.acos(cos_theta)

    #gamma is the angle formed by an horizontal axis and de
    tan_gamma = (ye-yd)/float(xe-xd)
    gamma = math.atan(tan_gamma)

    #lambda is the angle formed by an horizontal axis and the left long arm
    lam = theta + gamma
    xt = xd + a * math.cos(lam) - s * math.sin(lam)
    yt = yd + a * math.sin(lam) + s * math.cos(lam)

    return xt, yt