np.array of points to np.array of segments

Question

我有以下工作代码来将单个点投影到数组中的每个段。但我希望一组点中的每个点都投影到每个段上。

import numpy as np

#find closest segment to single point
  
#line segment
l1 = np.array([[2,3,0],[7,5,0]])   
l2 = np.array([[5,1,0],[8,6,0]])
#point that gets projected
p = np.array([[6,5,0]]) #only single point

#set to origin
line = l2-l1
pv = p-l1  

#length of line squared
len_sq = np.sum(line**2, axis = 1) #len_sq = numpy.einsum("ij,ij->i", line, line)

#dot product of 3D vectors with einsum
dot = np.einsum('ij,ij->i',line,pv) #np.sum(line*pv,axis=1)


#percentage of line the pv vector travels in
param = np.array([dot/len_sq])

#param<0 projected point=l1, param>1 pp=l2
clamped_param = np.clip(param,0,1)

#add line fraction to l1 to get projected point
pp = l1+(clamped_param.T*line)

例如，make

p = np.array([[6,5,0],[3,2,0]]) #multiple points

并返回4个投影点的np.array()。

Answer 1

也许你可以尝试一下下面这样的方法。如果project是一个可以对单个点执行操作的函数，那么通过使用沿轴应用，您可以让它在一个点数组中的所有点上工作。输出作为每个点的单独生成器产生，这些生成器必须使用堆叠操作转换回单个数组。

l1 = np.array([[2,3,0],[7,5,0]])   
l2 = np.array([[5,1,0],[8,6,0]])
line = l2-l1
len_sq = np.sum(line**2, axis = 1)

def project(p):
    pv = p-l1
    dot = np.einsum('ij,ij->i',line,pv) 
    param = np.array([dot/len_sq])
    clamped_param = np.clip(param,0,1)
    yield l1+(clamped_param.T*line)
    

pts = np.array([[6,5,0],
                [3,2,0]])

gen = np.apply_along_axis(project, 1, pts)
out = np.hstack([list(G) for G in gen])[0]