# 在3D绘图中绘制平面对象

演示如何使用pathpatch_2d_to_3d在3D绘图上“绘制”形状和文本。

![在3D绘图中绘制平面对象示例](https://matplotlib.org/_images/sphx_glr_pathpatch3d_001.png)

```python
import numpy as np
import matplotlib.pyplot as plt
from matplotlib.patches import Circle, PathPatch
from matplotlib.text import TextPath
from matplotlib.transforms import Affine2D
# This import registers the 3D projection, but is otherwise unused.
from mpl_toolkits.mplot3d import Axes3D  # noqa: F401 unused import
import mpl_toolkits.mplot3d.art3d as art3d


def text3d(ax, xyz, s, zdir="z", size=None, angle=0, usetex=False, **kwargs):
    '''
    Plots the string 's' on the axes 'ax', with position 'xyz', size 'size',
    and rotation angle 'angle'.  'zdir' gives the axis which is to be treated
    as the third dimension.  usetex is a boolean indicating whether the string
    should be interpreted as latex or not.  Any additional keyword arguments
    are passed on to transform_path.

    Note: zdir affects the interpretation of xyz.
    '''
    x, y, z = xyz
    if zdir == "y":
        xy1, z1 = (x, z), y
    elif zdir == "x":
        xy1, z1 = (y, z), x
    else:
        xy1, z1 = (x, y), z

    text_path = TextPath((0, 0), s, size=size, usetex=usetex)
    trans = Affine2D().rotate(angle).translate(xy1[0], xy1[1])

    p1 = PathPatch(trans.transform_path(text_path), **kwargs)
    ax.add_patch(p1)
    art3d.pathpatch_2d_to_3d(p1, z=z1, zdir=zdir)


fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')

# Draw a circle on the x=0 'wall'
p = Circle((5, 5), 3)
ax.add_patch(p)
art3d.pathpatch_2d_to_3d(p, z=0, zdir="x")

# Manually label the axes
text3d(ax, (4, -2, 0), "X-axis", zdir="z", size=.5, usetex=False,
       ec="none", fc="k")
text3d(ax, (12, 4, 0), "Y-axis", zdir="z", size=.5, usetex=False,
       angle=np.pi / 2, ec="none", fc="k")
text3d(ax, (12, 10, 4), "Z-axis", zdir="y", size=.5, usetex=False,
       angle=np.pi / 2, ec="none", fc="k")

# Write a Latex formula on the z=0 'floor'
text3d(ax, (1, 5, 0),
       r"$\displaystyle G_{\mu\nu} + \Lambda g_{\mu\nu} = "
       r"\frac{8\pi G}{c^4} T_{\mu\nu}  $",
       zdir="z", size=1, usetex=True,
       ec="none", fc="k")

ax.set_xlim(0, 10)
ax.set_ylim(0, 10)
ax.set_zlim(0, 10)

plt.show()
```

## 下载这个示例
            
- [下载python源码: pathpatch3d.py](https://matplotlib.org/_downloads/pathpatch3d.py)
- [下载Jupyter notebook: pathpatch3d.ipynb](https://matplotlib.org/_downloads/pathpatch3d.ipynb)