cpv.py 文件源码

def get_angle_formed_by(p1,p2,p3): # angle formed by three positions in space

    # based on code submitted by Paul Sherwood
    r1 = distance(p1,p2)
    r2 = distance(p2,p3)
    r3 = distance(p1,p3)

    small = 1.0e-10

    if (r1 + r2 - r3) < small:
        # This seems to happen occasionally for 180 angles 
        theta = math.pi
    else:
        theta = math.acos( (r1*r1 + r2*r2  - r3*r3) / (2.0 * r1*r2) )
    return theta;

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