#! /usr/bin/env python
"""Write (x,y,z) data from a Landlab grid + 1 field to a Wavefront OBJ file.
OBJ functions
+++++++++++++
.. autosummary::
~landlab.io.obj.write_obj
"""
import os
import pathlib
def _write_obj_vertices(file_like, xyz_at_vertex):
"""Write node (x,y,z) coordinates as OBJ vertices.
Parameters
----------
file_like : file-like
Opened file-like object to write vertices to.
xyz_at_vertex : array-like, shape *(n_vertices, 3)*
(x, y, z) values for each vertex.
"""
for x, y, z in xyz_at_vertex:
print(f"v {x} {y} {z}", file=file_like)
def _write_triangles_as_obj_faces(file_like, vertices_at_face):
"""Write triangular patches as OBJ faces.
OBJ format uses vertex/UVtexture/normal; latter two left blank here.
Parameters
----------
file_like : file-like
Opened file-like object to write faces to.
vertices_at_face : array-like of int, shape *(n_faces, 3)*
Vertex ids for each triangle.
"""
for vertex_0, vertex_1, vertex_2 in vertices_at_face:
print(f"f {vertex_0}// {vertex_1}// {vertex_2}//", file=file_like)
def _write_quads_as_obj_faces(file_, vertices_at_face):
"""Write quad patches as OBJ (triangle) faces.
Subdivide each patch into two triangles using vertices 0-1-2 (upper left)
and 2-3-0 (lower right).
OBJ format uses vertex/UVtexture/normal; latter two left blank here.
Parameters
----------
file_like : file-like
Opened file-like object to write faces to.
vertices_at_face : array-like of int, shape *(n_faces, 4)*
Vertex ids for each quadrilateral.
"""
for vertex_0, vertex_1, vertex_2, vertex_3 in vertices_at_face:
print(f"f {vertex_0}// {vertex_1}// {vertex_2}//", file=file_)
print(f"f {vertex_2}// {vertex_3}// {vertex_0}//", file=file_)
def _patches_are_triangles(grid):
"""Returns True if patches have 3 nodes, False otherwise."""
return grid.nodes_at_patch.shape[1] == 3
def _patches_are_quads(grid):
"""Returns True if patches have 4 nodes, False otherwise."""
return grid.nodes_at_patch.shape[1] == 4
[docs]
def write_obj(path, grid, field_for_z="topographic__elevation", clobber=False):
"""Write landlab grid and one field to Wavefront OBJ.
Parameters
----------
path : str, or file-like
Path to output file.
grid : Landlab grid object
Landlab grid object that includes associated values.
field_for_z : str, optional
Name of a field to use for the *z*-values of the OBJ file.
clobber : boolean, optional
If *path* exists, clobber the existing file, otherwise raise an
exception.
Returns
-------
str or file-like
The input path used to write the OBJ file.
Examples
--------
>>> import io
>>> from landlab import HexModelGrid, RasterModelGrid
>>> from landlab.io.obj import write_obj
>>> grid = HexModelGrid((3, 2), spacing=2.0)
>>> z = grid.add_zeros("topographic__elevation", at="node")
>>> z[3] = 1.0
>>> obj_file = write_obj(io.StringIO(), grid)
>>> print(obj_file.getvalue())
# landlabgrid
#
g landlabgrid
v 1.0 0.0 0.0
v 3.0 0.0 0.0
v 0.0 1.732051 0.0
v 2.0 1.732051 1.0
v 4.0 1.732051 0.0
v 1.0 3.464102 0.0
v 3.0 3.464102 0.0
f 4// 1// 2//
f 4// 3// 1//
f 5// 4// 2//
f 6// 3// 4//
f 7// 4// 5//
f 7// 6// 4//
<BLANKLINE>
"""
if not (_patches_are_triangles(grid) or _patches_are_quads(grid)):
raise TypeError("grid faces must be triangles or quads")
z_at_node = grid.at_node[field_for_z]
if isinstance(path, (str, pathlib.Path)):
if os.path.exists(path) and not clobber:
raise ValueError(f"file exists ({path})")
with open(path, "w") as fp:
_write_obj_to_filelike(fp, grid, z_at_node)
else:
_write_obj_to_filelike(path, grid, z_at_node)
return path
def _write_obj_to_filelike(file_like, grid, z_at_node):
file_like.write("# landlabgrid\n")
file_like.write("#\n")
file_like.write("g landlabgrid\n")
_write_obj_vertices(file_like, zip(grid.x_of_node, grid.y_of_node, z_at_node))
if _patches_are_triangles(grid):
_write_triangles_as_obj_faces(file_like, grid.nodes_at_patch + 1)
elif _patches_are_quads(grid):
_write_quads_as_obj_faces(file_like, grid.nodes_at_patch + 1)