import pathlib
from io import BytesIO
import numpy as np
from cfdmod.utils import create_folders_for_file
__all__ = ["export_stl", "read_stl"]
[docs]
def read_stl(filename: pathlib.Path) -> tuple[np.ndarray, np.ndarray]:
"""Read buffer content as STL file
Args:
buff (io.BufferedReader): buffer to read from
Returns:
tuple[np.ndarray, np.ndarray]: return STL representation as (triangles, normals).
"""
# pass header
with open(filename, "rb") as f:
buff = BytesIO(f.read())
buff.read(80) # Header
# Read number of triangles
n_triangles = np.frombuffer(buff.read(4), dtype=np.uint32)[0]
if n_triangles == 0:
raise ValueError("Unable to read number of triangles as 0")
triangles = np.empty((n_triangles, 3, 3), dtype=np.float32)
normals = np.empty((n_triangles, 3), dtype=np.float32)
for idx in range(n_triangles):
content = buff.read(50)
normal = np.frombuffer(content[0:12], dtype=np.float32)
triangle = np.frombuffer(content[12:48], dtype=np.float32).reshape((3, 3))
triangles[idx] = triangle
normals[idx] = normal
return triangles, normals
[docs]
def export_stl(filename: pathlib.Path, triangle_vertices: np.ndarray, normals: np.ndarray):
"""Export geometry in STL format
Args:
filename (pathlib.Path): Filename to save to.
triangle_vertices (np.ndarray): Array of the vertices of the triangles.
normals (np.ndarray): Array of triangles normals.
"""
# 80 bytes header
HEADER = b"\x00" * 80
n_triangles = len(triangle_vertices)
# STL content is header + uint32 + 50 bytes per triangle
stl_content = bytearray(len(HEADER) + 4 + 50 * n_triangles)
# Add header and number of triangles
stl_content[: len(HEADER)] = HEADER
stl_content[len(HEADER) : len(HEADER) + 4] = np.uint32(n_triangles).tobytes()
idx_curr = len(HEADER) + 4
for idx, t_verts in enumerate(triangle_vertices):
p0, p1, p2 = [t_verts[0], t_verts[1], t_verts[2]]
normal = normals[idx]
t_arr = np.array([normal, p0, p1, p2], dtype=np.float32)
# Add triangles to STL content and 2 bytes padding
stl_content[idx_curr : idx_curr + 50] = t_arr.tobytes("C") + b"\x00\x00"
idx_curr += 50
create_folders_for_file(filename)
with open(filename, "wb") as f:
f.write(bytes(stl_content))
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