Source code for pyxfem.core.geometry

import numpy as np



def cross2d(a, b):
    return a[..., 0] * b[..., 1] - a[..., 1] * b[..., 0]




def is_left_to_line(a, b, c) :
    ''' given three point a, b, c return true if c is on the right of segment ab '''
    return cross2d(b-a, c-a) >= 0.

    


def is_in_triangle(t, a) :
    ''' return true if point a is in triangle t '''
    return is_left_to_line(t[0], t[1], a) & is_left_to_line(t[1], t[2], a) & is_left_to_line(t[2], t[0], a)


if __name__ == "__main__":
    print(is_left_to_line(np.array([0.1,0]),np.array([1., 0.]), np.array([0.,1.])))
    t1 = np.array([[0.1,0.],[1.,0.],[0.,1.]])
    t2 = np.array([[1.1,0.],[2.,0.],[1.,1.]])
    tris = np.array([t1, t2])
    print(is_left_to_line(t1[0], t1[1], np.array([[1.,0.3], [0.1, -0.3]]) ))

    print(t2)

    print(is_in_triangle(t1, np.array([[1.,0.3], [0.1, 0.3]])))
    print(is_in_triangle(tris, np.array([[1.,0.3], [0.1, 0.3]])))