docs: update README

load/tets/generate_tets.py

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+# Copyright (c) 2020-2022 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+#
+# NVIDIA CORPORATION, its affiliates and licensors retain all intellectual
+# property and proprietary rights in and to this material, related
+# documentation and any modifications thereto. Any use, reproduction,
+# disclosure or distribution of this material and related documentation
+# without an express license agreement from NVIDIA CORPORATION or
+# its affiliates is strictly prohibited.
+
+import os
+
+import numpy as np
+
+"""
+This code segment shows how to use Quartet: https://github.com/crawforddoran/quartet,
+to generate a tet grid
+1) Download, compile and run Quartet as described in the link above. Example usage `quartet meshes/cube.obj 0.5 cube_5.tet`
+2) Run the function below to generate a file `cube_32_tet.tet`
+"""
+
+
+def generate_tetrahedron_grid_file(res=32, root=".."):
+    frac = 1.0 / res
+    command = f"cd {root}; ./quartet meshes/cube.obj {frac} meshes/cube_{res}_tet.tet -s meshes/cube_boundary_{res}.obj"
+    os.system(command)
+
+
+"""
+This code segment shows how to convert from a quartet .tet file to compressed npz file
+"""
+
+
+def convert_from_quartet_to_npz(quartetfile="cube_32_tet.tet", npzfile="32_tets"):
+    file1 = open(quartetfile, "r")
+    header = file1.readline()
+    numvertices = int(header.split(" ")[1])
+    numtets = int(header.split(" ")[2])
+    print(numvertices, numtets)
+
+    # load vertices
+    vertices = np.loadtxt(quartetfile, skiprows=1, max_rows=numvertices)
+    print(vertices.shape)
+
+    # load indices
+    indices = np.loadtxt(
+        quartetfile, dtype=int, skiprows=1 + numvertices, max_rows=numtets
+    )
+    print(indices.shape)
+
+    np.savez_compressed(npzfile, vertices=vertices, indices=indices)
+
+
+root = "/home/gyc/quartet"
+for res in [300, 350, 400]:
+    generate_tetrahedron_grid_file(res, root)
+    convert_from_quartet_to_npz(
+        os.path.join(root, f"meshes/cube_{res}_tet.tet"), npzfile=f"{res}_tets"
+    )