import tensorflow as tf
import numpy as np
def distance_matrix(array1, array2):
"""
arguments:
array1: the array, size: (num_point, num_feature)
array2: the samples, size: (num_point, num_feature)
returns:
distances: each entry is the distance from a sample to array1
, it's size: (num_point, num_point)
"""
num_point, num_features = array1.shape
expanded_array1 = tf.tile(array1, (num_point, 1))
expanded_array2 = tf.reshape(
tf.tile(tf.expand_dims(array2, 1),
(1, num_point, 1)),
(-1, num_features))
distances = tf.norm(expanded_array1-expanded_array2, axis=1)
distances = tf.reshape(distances, (num_point, num_point))
return distances
def av_dist(array1, array2):
"""
arguments:
array1, array2: both size: (num_points, num_feature)
returns:
distances: size: (1,)
"""
distances = distance_matrix(array1, array2)
distances = tf.reduce_min(distances, axis=1)
distances = tf.reduce_mean(distances)
return distances
def av_dist_sum(arrays):
"""
arguments:
arrays: array1, array2
returns:
sum of av_dist(array1, array2) and av_dist(array2, array1)
"""
array1, array2 = arrays
av_dist1 = av_dist(array1, array2)
av_dist2 = av_dist(array2, array1)
return av_dist1+av_dist2
def chamfer_distance_tf(array1, array2):
batch_size, num_point, num_features = array1.shape
dist = tf.reduce_mean(
tf.map_fn(av_dist_sum, elems=(array1, array2), dtype=tf.float64)
)
return dist
def array2samples_distance(array1, array2):
"""
arguments:
array1: the array, size: (num_point, num_feature)
array2: the samples, size: (num_point, num_feature)
returns:
distances: each entry is the distance from a sample to array1
"""
num_point, num_features = array1.shape
expanded_array1 = np.tile(array1, (num_point, 1))
expanded_array2 = np.reshape(
np.tile(np.expand_dims(array2, 1),
(1, num_point, 1)),
(-1, num_features))
distances = np.linalg.norm(expanded_array1-expanded_array2, axis=1)
distances = np.reshape(distances, (num_point, num_point))
distances = np.min(distances, axis=1)
distances = np.mean(distances)
return distances
def chamfer_distance_numpy(array1, array2):
batch_size, num_point, num_features = array1.shape
dist = 0
for i in range(batch_size):
av_dist1 = array2samples_distance(array1[i], array2[i])
av_dist2 = array2samples_distance(array2[i], array1[i])
dist = dist + (av_dist1+av_dist2)/batch_size
return dist
if __name__=='__main__':
batch_size = 3
num_point = 10
num_features = 3
np.random.seed(1)
array1 = np.random.randint(0, high=4, size=(batch_size, num_point, num_features))
array2 = np.random.randint(0, high=4, size=(batch_size, num_point, num_features))
print (array1)
#print(array2)
print('numpy: ', chamfer_distance_numpy(array1, array2))
