用颜色在单位球体上绘制数据

Question

您好，我有一个包含三列的数据集：theta、phi 以及 theta 和 phi 处的函数值。我想将此数据投影到一个单位球体上，以便球体上的颜色对应于函数的大小，类似于this post。我提供的样本数据的性质是球体的上半部和下半部的值是相同的，因此期望球体的上半部和下半部的颜色分布是相同的，但由于某种原因，我发现虽然形状正确，但由于某种原因，上半部分更亮（见下图）。有谁知道为什么会这样？

数据集：

Theta     Phi      Values
0.000000 -3.141592 0.500000
0.000000 -3.078126 0.500000
0.000000 -3.014659 0.500000
...    ...  ...
0.031733 -3.141592 0.499497
0.031733 -3.078126 0.499497
0.031733 -3.014659 0.499497
...    ...  ...
0.507732 -0.031733 0.388763
0.507732  0.031734 0.388763
0.507732  0.095200 0.388541
...    ...  ...
1.364530 -0.095199 0.131597
1.364530 -0.031733 0.135245
1.364530 0.031734 0.135245
1.364530 0.095200 0.131597
...    ...  ...
2.633860 -0.095199 0.388541
2.633860 -0.031733 0.388763
2.633860  0.031734 0.388763
...    ...  ...    
3.109859 3.014660 0.499497
3.109859 3.078126 0.499497
3.109859 3.141593 0.499497
...    ...  ...
3.141592 3.014660 0.500000
3.141592 3.078126 0.500000
3.141592 3.141593 0.500000

代码：

from numpy import*
import math
import matplotlib.pyplot as plt
from matplotlib import cm
from mpl_toolkits.mplot3d import Axes3D
import numpy as np
import matplotlib.cm as cm

#theta inclination angle
#phi azimuthal angle
n_theta = 100 #number of values for theta
n_phi = 100  #number of values for phi
r = 1        #radius of sphere

theta, phi = np.mgrid[0: pi:n_theta*1j,-pi:pi:n_phi*1j ]

x = r*np.sin(theta)*np.cos(phi)
y = r*np.sin(theta)*np.sin(phi)
z = r*np.cos(theta)

print theta.shape 
print phi.shape 

inp = []
f = open("datafile.dat","r")
for line in f:
    i = float(line.split()[0])
    j = float(line.split()[1])
    val = float(line.split()[2])
    inp.append([i, j, val])

inp = np.array(inp)
#print inp
#print inp.shape

#reshape the input array to the shape of the x,y,z arrays. 
c = inp[:,2].reshape((n_phi,n_theta))

#Set colours and render
fig = plt.figure(figsize=(10, 8))
ax = fig.add_subplot(111, projection='3d')

surf = ax.plot_surface(
    x,y,z,  rstride=1, cstride=1, facecolors=cm.hot(c), alpha=0.9, linewidth=1) 
ax.set_xlim([-2.0,2.0])
ax.set_ylim([-2.0,2.0])
ax.set_zlim([-2,2])
ax.set_aspect("equal")

plt.title('Projecting data on unit sphere')

#Label axis. 
ax.set_xlabel('X')
ax.set_ylabel('Y')
ax.set_zlabel('Z')

#Creates array for colorbar from 0 to 1. 
a = array( [1.0, 0.5, 0.0])

#Creates colorbar
m = cm.ScalarMappable(cmap=cm.hot)
m.set_array(a)
plt.colorbar(m)
plt.savefig('Projecting data on unit sphere.png')

f.close()
plt.show()

Answer 1

您需要将plot_surface的shade参数设置为False，

ax.plot_surface(..., shade=False)

否则会在您的表面顶部模拟一些灯光效果，这取决于视角。