Question

我有一个令人沮丧的问题，只有在3D轴上绘制填充的等高线图时才能显示出来，并且仅在某些情况下。

以下是我遇到的问题的一个示例：

和

这些是不同轮廓间隔的相同数据。您会注意到域的左侧发生了错误填充。这是一个Z点通过像

这样的绘图命令压入Z = 0平面的图

ax3d.contourf(X, Y, dbz[z25,:,:], zdir='z', offset=0, levels=levels, cmap='pymeteo_radar', alpha=0.50)

无论使用alpha级别或色彩映射，都会发生错误调整，但对级别数量敏感。 zdir和offset的使用不会影响错误轮廓（假象只发生在Z曲面上。如果我没有填充轮廓，则没有错误轮廓。我也可以改变域有时会使问题变得更好（或更糟），但我在同一个域内有许多图表，所以这不是一个修复。

在2D轴上绘制相同数据时不会发生此问题，例如：

此图上有一些额外的数据，但您可以看到填充的轮廓线不会因误填充在3D轴上发生的轮廓而产生相同的伪影。

以下是您可以运行以重现该问题的脚本。

#!/usr/bin/env python
import numpy as np
import matplotlib.pyplot as plt
import mpl_toolkits.mplot3d.axes3d as p3

data=np.array([[53.9751,  51.5681,  50.7119,  51.1049,  51.5339,  51.4977,  51.2387,50.761,  50.1732,  49.8218,  49.5442,  48.936,  47.4498,  46.6484, 45.8542,  45.136,  44.5268,  44.071,  43.7665,  43.5928,  43.5269, 43.5385,  43.6053,  45.565,  47.0071,  46.8664,  47.372,  47.8324, 48.295,  48.731,  49.0522,  49.4001,  49.7111,  49.9919,  50.2527, 50.4928,  50.7135,  50.8831,  51.0806,  51.2683 ],
               [55.6671,  52.53,  50.7764,  50.5632,  51.2095,  51.5659,  51.521,  51.2143,  50.653,  50.2371,  49.989,  49.8089,  49.6058,  47.8355, 47.3124,  46.7346,  46.1616,  45.6498,  45.2462,  44.967,  44.8005, 44.7284,  44.7295,  44.7869,  46.959,  45.0194,  46.73,  48.0766, 48.9395,  49.5325,  49.8498,  50.1887,  50.4798,  50.7406,  50.9808, 51.2003,  51.4074,  51.555,  51.7429,  51.9218 ],
               [56.6513,  53.5919,  51.2774,  50.3133,  50.7705,  51.533,  51.8287, 51.7083,  51.2816,  50.7933,  50.4806,  50.2671,  50.1009,  50.0096, 49.9052,  49.4698,  47.4655,  47.0717,  46.6849,  46.3583,  46.1122, 45.952,  45.8678,  45.8485,  45.8811,  45.956,  46.0634,  47.2225, 49.4363,  50.2482,  50.527,  50.8558,  51.1358,  51.3809,  51.607, 51.8179,  52.0161,  52.1454,  52.3263,  52.497 ],
               [57.078,  54.3224,  52.0759,  50.4679,  50.4677,  51.297,  52.0284, 52.1594,  51.9395,  51.5518,  51.1419,  50.8765,  50.6686,  50.5101, 50.4078,  50.3473,  50.3592,  50.3813,  49.7504,  47.55,  47.324, 47.1365,  46.9978,  46.9119,  46.8743,  46.8811,  46.9257,  47.0013, 50.0148,  50.9106,  51.1133,  51.4282,  51.7064,  51.943,  52.1587, 52.3597,  52.4789,  52.6631,  52.8359,  52.9966 ],
               [57.3835,  54.9025,  52.8571,  50.9842,  50.5197,  51.1494,  52.0599, 52.4732,  52.4716,  52.2656,  51.9535,  51.6068,  51.3466,  51.1513, 50.9708,  50.8321,  50.7639,  50.7944,  50.8817,  49.8122,  48.2038, 48.086,  47.9704,  47.8735,  47.8035,  47.7644,  47.7574,  47.7803, 50.8194,  51.5486,  51.6645,  51.9745,  52.2349,  52.4508,  52.6481, 52.8317,  52.9412,  53.1097,  53.2699,  53.4171 ],
               [57.9157,  55.6092,  53.6306,  51.8011,  50.9372,  51.2615,  52.1406, 52.7436,  52.8528,  52.7829,  52.6322,  52.403,  52.1149,  51.866, 51.6624,  51.4773,  51.317,  51.2183,  51.2153,  51.1367,  48.5913, 48.6216,  48.6218,  48.5951,  48.5589,  48.527,  48.5081,  50.5185, 51.6998,  51.905,  52.2258,  52.4891,  52.7062,  52.8926,  53.0655, 53.2251,  53.3262,  53.4755,  53.6169,  53.7471 ],
               [58.6093,  56.432,  54.307,  52.6277,  51.584,  51.6482,  52.3762, 53.0685,  53.2545,  53.217,  53.1356,  53.0351,  52.8481,  52.6154, 52.39,  52.177,  51.9977,  51.843,  51.7172,  51.4587,  48.7481,  48.7984, 48.864,  48.9291,  48.9843,  49.0228,  50.496,  51.8667,  52.3404, 52.4759,  52.6889,  52.8851,  53.0525,  53.2072,  53.354,  53.4576, 53.5925,  53.7217,  53.8432,  53.956 ],
               [58.9719,  56.9885,  54.8768,  53.3526,  52.3025,  52.2089,  52.7762, 53.4444,  53.6768,  53.6706,  53.5692,  53.5162,  53.4373,  53.2886, 53.1113,  52.9065,  52.6988,  52.5193,  52.3544,  52.0384,  48.9624, 48.9653,  49.0005,  49.0574,  49.1258,  50.692,  51.9726,  52.4309, 52.699,  52.8194,  52.9845,  53.1336,  53.2669,  53.393,  53.5118, 53.6086,  53.7213,  53.8293,  53.9308,  54.026 ],
              [58.5754,  56.945,  55.068,  53.7798,  52.9469,  52.854,  53.3136,53.8929,  54.1205,  54.1178,  54.0128,  53.9289,  53.8906,  53.8239,53.717,  53.5724,  53.3818,  53.1892,  53.009,  49.3078,  49.2524,49.2165,  49.2032,  49.2187,  50.463,  51.9497,  52.4487,  52.7041,52.8358,  52.9776,  53.1101,  53.2293,  53.3419,  53.4487,  53.5401,53.6365,  53.7301,  53.8205,  53.9062,  53.9869 ],
              [57.623,  56.547,  55.0117,  54.0512,  53.5372,  53.5246,  53.927,54.3868,  54.5828,  54.5811,  54.4501,  54.3235,  54.2626,  54.2334,54.1802,  54.1137,  53.9897,  53.8202,  49.796,  49.6864,  49.5946,49.5216,  49.4703,  49.4432,  51.8479,  52.5574,  52.8359,  52.9722,53.0827,  53.1826,  53.2747,  53.3597,  53.4405,  53.5138,  53.5944,53.6751,  53.7536,  53.829,  53.9019,  53.9721 ],
              [56.902,  56.0005,  54.9159,  54.3352,  54.123,  54.2014,  54.5659,54.8917,  55.0307,  55.0139,  54.8838,  54.7044,  54.5863,  54.5548,54.5258,  54.4957,  54.4633,  51.4821,  50.1897,  50.0758,  49.9683,49.8704,  49.7842,  51.5064,  52.7625,  53.0724,  53.1926,  53.2682,53.3404,  53.4119,  53.4831,  53.5517,  53.6169,  53.6763,  53.7383,53.8009,  53.8644,  53.9281,  53.9905,  54.0517 ],
              [56.3455,  55.5524,  54.9336,  54.6836,  54.703,  54.8657,  55.1749,55.3844,  55.4521,  55.4019,  55.2622,  55.0281,  54.8981,  54.6591,54.7866,  54.7678,  54.7654,  54.0436,  54.2302,  52.2533,  50.3305,50.2276,  50.1268,  52.9617,  53.4395,  53.5504,  53.5481,  53.5524,53.5699,  53.6014,  53.644,  53.6931,  53.7445,  53.7996,  53.8548,53.9097,  53.9655,  54.0229,  54.0813,  54.1393 ],
              [55.7493,  55.3019,  55.1012,  55.0906,  55.234,  55.4751,  55.7134,55.8462,  55.8461,  55.7425,  55.5725,  55.3535,  55.1612,  54.958,55.0193,  54.9584,  54.9531,  54.8886,  54.8256,  54.2211,  50.6477,50.5564,  53.0546,  53.8592,  54.08,  54.0288,  53.9509,  53.8796,53.8307,  53.8073,  53.8034,  53.8142,  53.8383,  53.8725,  53.9128,53.9558,  54.0013,  54.0497,  54.103,  54.1597 ],
              [55.2575,  55.1664,  55.3165,  55.5004,  55.7345,  55.9901,  56.1852,56.2599,  56.2027,  56.0454,  55.818,  55.5754,  55.302,  55.2083,55.0224,  55.1415,  55.0656,  55.0446,  55.0263,  54.7728,  50.8924,53.4671,  54.2587,  54.5146,  54.6171,  54.519,  54.3857,  54.2497,54.1355,  54.0509,  53.9932,  53.9584,  53.941,  53.939,  53.9527,53.9798,  54.0111,  54.0465,  54.0868,  54.1339 ],
              [54.8665,  55.1533,  55.5095,  55.8512,  56.1541,  56.3995,  56.5593,56.6009,  56.5079,  56.3001,  56.0178,  55.7187,  55.448,  55.063,55.2016,  55.2116,  55.1817,  55.112,  55.1099,  55.0299,  54.3358,54.6966,  54.9199,  55.0156,  55.0728,  54.975,  54.8299,  54.6609,54.493,  54.3475,  54.2349,  54.1517,  54.0928,  54.0516,  54.0245,54.013,  54.0206,  54.0404,  54.0667,  54.0989 ],
              [54.2676,  55.1132,  55.6112,  56.09,  56.428,  56.6661,  56.8056,56.8374,  56.7339,  56.4923,  56.1474,  55.7977,  55.4805,  55.2341,54.8999,  55.2662,  55.2927,  55.185,  55.1237,  55.1268,  54.9772,55.1418,  55.2612,  55.3333,  55.379,  55.3244,  55.2153,  55.0629,54.881,  54.6926,  54.523,  54.3866,  54.2855,  54.2118,  54.1583,54.1191,  54.0935,  54.0834,  54.0885,  54.1057 ],
              [54.1771,  55.0795,  55.7075,  56.1772,  56.5183,  56.7522,  56.8898,56.9315,  56.8427,  56.6056,  56.2317,  55.8095,  55.4436,  55.183,55.0284,  54.9504,  55.2833,  55.2563,  55.1498,  55.1342,  55.1331,55.259,  55.3705,  55.4452,  55.4955,  55.5087,  55.4697,  55.3766,55.2324,  55.049,  54.8485,  54.6578,  54.4995,  54.3822,  54.3002,54.2427,  54.2022,  54.1749,  54.1598,  54.1561 ],
              [53.9112,  54.85,  55.6641,  56.0844,  56.4062,  56.6232,  56.757,56.8149,  56.7669,  56.5754,  56.2311,  55.785,  55.366,  55.0104,54.812,  54.8845,  55.1273,  55.2339,  55.1976,  55.1049,  55.0913,55.1843,  55.3048,  55.4076,  55.4709,  55.518,  55.5455,  55.5329,55.4636,  55.3349,  55.1595,  54.9529,  54.7462,  54.5681,  54.4342,54.3439,  54.2848,  54.2446,  54.2222,  54.2135 ],
              [53.9368,  54.9196,  55.4408,  55.7999,  56.0652,  56.2423,  56.348,56.4106,  56.4114,  56.3028,  56.0519,  55.6779,  55.2493,  54.8836,54.6592,  54.6347,  54.8341,  55.0606,  55.1396,  55.0967,  55.0325,55.0501,  55.1451,  55.2627,  55.3559,  55.4216,  55.4789,  55.5183,55.5245,  55.4779,  55.3701,  55.2072,  55.0029,  54.7876,  54.5915,54.4378,  54.3368,  54.2787,  54.2415,  54.2271 ],
              [53.9325,  54.6506,  55.0421,  55.2926,  55.4603,  55.5679,  55.6285,55.6792,  55.7234,  55.731,  55.639,  55.3923,  55.043,  54.6845,54.4188,  54.3242,  54.4606,  54.7449,  54.9548,  55.0171,  55.0047,54.9454,  54.9666,  55.0651,  55.1828,  55.2677,  55.3308,  55.3914,55.438,  55.4544,  55.4277,  55.3385,  55.1907,  54.9981,  54.7786,54.5691,  54.4013,  54.2898,  54.233,  54.1994 ] ])

fig = plt.figure()
ax = fig.add_subplot(111,projection='3d')
X,Y = np.meshgrid(np.arange(-30.0,-20.0,0.25), np.arange(20.0,25,0.25))
ax.contourf(X,Y,data,zdir='z',offset=0, levels=np.arange(0,75,1))
ax.set_zlim(0.0,2.0)
plt.savefig('testfig.png')
plt.close()

此代码将生成图：

在所有情况下，我都观察到这种错误轮廓，坏三角形总是在域的左下角附近有一个顶点。我的数据经常被网格化，并且所讨论的域在X和Y中是均匀的。在这种情况下，如果轮廓水平的数量减少，则误填充将消失。在其他一些情况下，这并不总是有帮助或只是改变错误的视觉外观。在任何情况下，即使是非常粗糙的轮廓，我仍然会在我的一部分图中出现错误。

有没有人见过这个并找到了解决方法？我忽略了什么吗？我愿意采用不涉及降低轮廓水平的解决方法（这确实可以减少整体错误）。如果其他人同意这可能是mplot3d中的错误，我将向他们提交错误报告（Issue opened here）。我感觉问题在于levels选项导致密集轮廓时轮廓非常强的渐变，但奇怪的是仅在3d轴上。

修改

第二个想法可能是matplotlib正在尝试计算轮廓多边形，而不是仅仅在逐个纹理元素的基础上计算背景纹理，这可能会导致依赖于值的烦人的准确性问题。相反，绘制轮廓线要容易得多，因为您可以在行进方形方法中计算线段，而无需担心重建完整的轮廓线拓扑（例如，如果线轮廓图中缺少非常小的线段，则表示您不会无论如何都要注意。）

如果这确实是错误，那么修复可能并不容易，因为需要以完全不同的（即使更简单的）方式完全重新实现平面绘图。

Answer 2

这在matplotlib.mplot3d中是一个长期存在的错误，在获取2D contourf集并将其扩展为3D时会忽略路径信息。在某些情况下，这导致带有孔的路径在路径段意图作为“移动”时不正确地呈现。而是＃34;绘制＆＃34;。

I contributed a fix对于matplotlib的这个问题，这个bug在matplotlib 1.5.0稳定版中得到修复。

与问题中相同的测试代码使用matplotlib 1.5生成正确的绘图，如下所示：

三维轴上填充等高线图中的伪像

2 个答案:

修改