[Feature] Add rectangle and triangle sdf_func

[AndPuQing]

PR types

New features

PR changes

APIs

Describe

In this pull request, I have added the sdf_func implementations for rectangles and triangles. The visual result can be tested using the following code:

import ppsci
import numpy as np

from matplotlib import pyplot as plt

geo = ppsci.geometry.Triangle((0, 0), (1, 0), (0, 1))

x = np.linspace(-0.5, 1.3, 1000)
y = np.linspace(-0.5, 1.3, 1000)
X, Y = np.meshgrid(x, y)
x = X.flatten()
y = Y.flatten()
Z = geo.sdf_func(np.stack([x, y], axis=-1)).reshape(X.shape)
plt.contour(X, Y, Z, 0, colors="black")
plt.contourf(X, Y, Z, 20, cmap="RdBu_r")
plt.colorbar()
plt.show()

Visual Result

#376

[paddle-bot]

Thanks for your contribution!

[HydrogenSulfate]

变量名字建议不要单个小写字母，命名尽量能表明变量本身的意义

[HydrogenSulfate]

变量名字建议不要单个小写字母，命名尽量能表明变量本身的意义

[HydrogenSulfate]

LGTM