# Copyright (c) Facebook, Inc. and its affiliates. All rights reserved. """This module implements utility functions for loading and saving meshes.""" import os import warnings from collections import namedtuple from typing import Optional import numpy as np import torch from pytorch3d.io.mtl_io import load_mtl, make_mesh_texture_atlas from pytorch3d.io.utils import _open_file from pytorch3d.structures import Meshes, Textures, join_meshes_as_batch def _make_tensor(data, cols: int, dtype: torch.dtype, device="cpu") -> torch.Tensor: """ Return a 2D tensor with the specified cols and dtype filled with data, even when data is empty. """ if not data: return torch.zeros((0, cols), dtype=dtype, device=device) return torch.tensor(data, dtype=dtype, device=device) # Faces & Aux type returned from load_obj function. _Faces = namedtuple("Faces", "verts_idx normals_idx textures_idx materials_idx") _Aux = namedtuple( "Properties", "normals verts_uvs material_colors texture_images texture_atlas" ) def _format_faces_indices(faces_indices, max_index, device, pad_value=None): """ Format indices and check for invalid values. Indices can refer to values in one of the face properties: vertices, textures or normals. See comments of the load_obj function for more details. Args: faces_indices: List of ints of indices. max_index: Max index for the face property. Returns: faces_indices: List of ints of indices. Raises: ValueError if indices are not in a valid range. """ faces_indices = _make_tensor( faces_indices, cols=3, dtype=torch.int64, device=device ) if pad_value: mask = faces_indices.eq(pad_value).all(-1) # Change to 0 based indexing. faces_indices[(faces_indices > 0)] -= 1 # Negative indexing counts from the end. faces_indices[(faces_indices < 0)] += max_index if pad_value: faces_indices[mask] = pad_value # Check indices are valid. if torch.any(faces_indices >= max_index) or torch.any(faces_indices < 0): warnings.warn("Faces have invalid indices") return faces_indices def load_obj( f_obj, load_textures=True, create_texture_atlas: bool = False, texture_atlas_size: int = 4, texture_wrap: Optional[str] = "repeat", device="cpu", ): """ Load a mesh from a .obj file and optionally textures from a .mtl file. Currently this handles verts, faces, vertex texture uv coordinates, normals, texture images and material reflectivity values. Note .obj files are 1-indexed. The tensors returned from this function are 0-indexed. OBJ spec reference: http://www.martinreddy.net/gfx/3d/OBJ.spec Example .obj file format: :: # this is a comment v 1.000000 -1.000000 -1.000000 v 1.000000 -1.000000 1.000000 v -1.000000 -1.000000 1.000000 v -1.000000 -1.000000 -1.000000 v 1.000000 1.000000 -1.000000 vt 0.748573 0.750412 vt 0.749279 0.501284 vt 0.999110 0.501077 vt 0.999455 0.750380 vn 0.000000 0.000000 -1.000000 vn -1.000000 -0.000000 -0.000000 vn -0.000000 -0.000000 1.000000 f 5/2/1 1/2/1 4/3/1 f 5/1/1 4/3/1 2/4/1 The first character of the line denotes the type of input: :: - v is a vertex - vt is the texture coordinate of one vertex - vn is the normal of one vertex - f is a face Faces are interpreted as follows: :: 5/2/1 describes the first vertex of the first triange - 5: index of vertex [1.000000 1.000000 -1.000000] - 2: index of texture coordinate [0.749279 0.501284] - 1: index of normal [0.000000 0.000000 -1.000000] If there are faces with more than 3 vertices they are subdivided into triangles. Polygonal faces are assummed to have vertices ordered counter-clockwise so the (right-handed) normal points out of the screen e.g. a proper rectangular face would be specified like this: :: 0_________1 | | | | 3 ________2 The face would be split into two triangles: (0, 2, 1) and (0, 3, 2), both of which are also oriented counter-clockwise and have normals pointing out of the screen. Args: f: A file-like object (with methods read, readline, tell, and seek), a pathlib path or a string containing a file name. load_textures: Boolean indicating whether material files are loaded create_texture_atlas: Bool, If True a per face texture map is created and a tensor `texture_atlas` is also returned in `aux`. texture_atlas_size: Int specifying the resolution of the texture map per face when `create_texture_atlas=True`. A (texture_size, texture_size, 3) map is created per face. texture_wrap: string, one of ["repeat", "clamp"]. This applies when computing the texture atlas. If `texture_mode="repeat"`, for uv values outside the range [0, 1] the integer part is ignored and a repeating pattern is formed. If `texture_mode="clamp"` the values are clamped to the range [0, 1]. If None, then there is no transformation of the texture values. device: string or torch.device on which to return the new tensors. Returns: 6-element tuple containing - **verts**: FloatTensor of shape (V, 3). - **faces**: NamedTuple with fields: - verts_idx: LongTensor of vertex indices, shape (F, 3). - normals_idx: (optional) LongTensor of normal indices, shape (F, 3). - textures_idx: (optional) LongTensor of texture indices, shape (F, 3). This can be used to index into verts_uvs. - materials_idx: (optional) List of indices indicating which material the texture is derived from for each face. If there is no material for a face, the index is -1. This can be used to retrieve the corresponding values in material_colors/texture_images after they have been converted to tensors or Materials/Textures data structures - see textures.py and materials.py for more info. - **aux**: NamedTuple with fields: - normals: FloatTensor of shape (N, 3) - verts_uvs: FloatTensor of shape (T, 2), giving the uv coordinate per vertex. If a vertex is shared between two faces, it can have a different uv value for each instance. Therefore it is possible that the number of verts_uvs is greater than num verts i.e. T > V. vertex. - material_colors: if `load_textures=True` and the material has associated properties this will be a dict of material names and properties of the form: .. code-block:: python { material_name_1: { "ambient_color": tensor of shape (1, 3), "diffuse_color": tensor of shape (1, 3), "specular_color": tensor of shape (1, 3), "shininess": tensor of shape (1) }, material_name_2: {}, ... } If a material does not have any properties it will have an empty dict. If `load_textures=False`, `material_colors` will None. - texture_images: if `load_textures=True` and the material has a texture map, this will be a dict of the form: .. code-block:: python { material_name_1: (H, W, 3) image, ... } If `load_textures=False`, `texture_images` will None. - texture_atlas: if `load_textures=True` and `create_texture_atlas=True`, this will be a FloatTensor of the form: (F, texture_size, textures_size, 3) If the material does not have a texture map, then all faces will have a uniform white texture. Otherwise `texture_atlas` will be None. """ data_dir = "./" if isinstance(f_obj, (str, bytes, os.PathLike)): # pyre-fixme[6]: Expected `_PathLike[Variable[typing.AnyStr <: [str, # bytes]]]` for 1st param but got `Union[_PathLike[typing.Any], bytes, str]`. data_dir = os.path.dirname(f_obj) f_obj, new_f = _open_file(f_obj, "r") try: return _load( f_obj, data_dir, load_textures=load_textures, create_texture_atlas=create_texture_atlas, texture_atlas_size=texture_atlas_size, texture_wrap=texture_wrap, device=device, ) finally: if new_f: f_obj.close() def load_objs_as_meshes(files: list, device=None, load_textures: bool = True): """ Load meshes from a list of .obj files using the load_obj function, and return them as a Meshes object. This only works for meshes which have a single texture image for the whole mesh. See the load_obj function for more details. material_colors and normals are not stored. Args: f: A list of file-like objects (with methods read, readline, tell, and seek), pathlib paths or strings containing file names. device: Desired device of returned Meshes. Default: uses the current device for the default tensor type. load_textures: Boolean indicating whether material files are loaded Returns: New Meshes object. """ mesh_list = [] for f_obj in files: # TODO: update this function to support the two texturing options. verts, faces, aux = load_obj(f_obj, load_textures=load_textures) verts = verts.to(device) tex = None tex_maps = aux.texture_images if tex_maps is not None and len(tex_maps) > 0: verts_uvs = aux.verts_uvs[None, ...].to(device) # (1, V, 2) faces_uvs = faces.textures_idx[None, ...].to(device) # (1, F, 3) image = list(tex_maps.values())[0].to(device)[None] tex = Textures(verts_uvs=verts_uvs, faces_uvs=faces_uvs, maps=image) mesh = Meshes(verts=[verts], faces=[faces.verts_idx.to(device)], textures=tex) mesh_list.append(mesh) if len(mesh_list) == 1: return mesh_list[0] return join_meshes_as_batch(mesh_list) def _parse_face( line, material_idx, faces_verts_idx, faces_normals_idx, faces_textures_idx, faces_materials_idx, ): face = line.split()[1:] face_list = [f.split("/") for f in face] face_verts = [] face_normals = [] face_textures = [] for vert_props in face_list: # Vertex index. face_verts.append(int(vert_props[0])) if len(vert_props) > 1: if vert_props[1] != "": # Texture index is present e.g. f 4/1/1. face_textures.append(int(vert_props[1])) if len(vert_props) > 2: # Normal index present e.g. 4/1/1 or 4//1. face_normals.append(int(vert_props[2])) if len(vert_props) > 3: raise ValueError( "Face vertices can ony have 3 properties. \ Face vert %s, Line: %s" % (str(vert_props), str(line)) ) # Triplets must be consistent for all vertices in a face e.g. # legal statement: f 4/1/1 3/2/1 2/1/1. # illegal statement: f 4/1/1 3//1 2//1. # If the face does not have normals or textures indices # fill with pad value = -1. This will ensure that # all the face index tensors will have F values where # F is the number of faces. if len(face_normals) > 0: if not (len(face_verts) == len(face_normals)): raise ValueError( "Face %s is an illegal statement. \ Vertex properties are inconsistent. Line: %s" % (str(face), str(line)) ) else: face_normals = [-1] * len(face_verts) # Fill with -1 if len(face_textures) > 0: if not (len(face_verts) == len(face_textures)): raise ValueError( "Face %s is an illegal statement. \ Vertex properties are inconsistent. Line: %s" % (str(face), str(line)) ) else: face_textures = [-1] * len(face_verts) # Fill with -1 # Subdivide faces with more than 3 vertices. # See comments of the load_obj function for more details. for i in range(len(face_verts) - 2): faces_verts_idx.append((face_verts[0], face_verts[i + 1], face_verts[i + 2])) faces_normals_idx.append( (face_normals[0], face_normals[i + 1], face_normals[i + 2]) ) faces_textures_idx.append( (face_textures[0], face_textures[i + 1], face_textures[i + 2]) ) faces_materials_idx.append(material_idx) def _load( f_obj, data_dir, load_textures: bool = True, create_texture_atlas: bool = False, texture_atlas_size: int = 4, texture_wrap: Optional[str] = "repeat", device="cpu", ): """ Load a mesh from a file-like object. See load_obj function more details. Any material files associated with the obj are expected to be in the directory given by data_dir. """ if texture_wrap is not None and texture_wrap not in ["repeat", "clamp"]: msg = "texture_wrap must be one of ['repeat', 'clamp'] or None, got %s" raise ValueError(msg % texture_wrap) lines = [line.strip() for line in f_obj] verts = [] normals = [] verts_uvs = [] faces_verts_idx = [] faces_normals_idx = [] faces_textures_idx = [] material_names = [] faces_materials_idx = [] f_mtl = None materials_idx = -1 # startswith expects each line to be a string. If the file is read in as # bytes then first decode to strings. if lines and isinstance(lines[0], bytes): lines = [l.decode("utf-8") for l in lines] for line in lines: if line.startswith("mtllib"): if len(line.split()) < 2: raise ValueError("material file name is not specified") # NOTE: only allow one .mtl file per .obj. # Definitions for multiple materials can be included # in this one .mtl file. f_mtl = os.path.join(data_dir, line.split()[1]) elif len(line.split()) != 0 and line.split()[0] == "usemtl": material_name = line.split()[1] # materials are often repeated for different parts # of a mesh. if material_name not in material_names: material_names.append(material_name) materials_idx = len(material_names) - 1 else: materials_idx = material_names.index(material_name) elif line.startswith("v "): # Line is a vertex. vert = [float(x) for x in line.split()[1:4]] if len(vert) != 3: msg = "Vertex %s does not have 3 values. Line: %s" raise ValueError(msg % (str(vert), str(line))) verts.append(vert) elif line.startswith("vt "): # Line is a texture. tx = [float(x) for x in line.split()[1:3]] if len(tx) != 2: raise ValueError( "Texture %s does not have 2 values. Line: %s" % (str(tx), str(line)) ) verts_uvs.append(tx) elif line.startswith("vn "): # Line is a normal. norm = [float(x) for x in line.split()[1:4]] if len(norm) != 3: msg = "Normal %s does not have 3 values. Line: %s" raise ValueError(msg % (str(norm), str(line))) normals.append(norm) elif line.startswith("f "): # Line is a face update face properties info. _parse_face( line, materials_idx, faces_verts_idx, faces_normals_idx, faces_textures_idx, faces_materials_idx, ) verts = _make_tensor(verts, cols=3, dtype=torch.float32, device=device) # (V, 3) normals = _make_tensor( normals, cols=3, dtype=torch.float32, device=device ) # (N, 3) verts_uvs = _make_tensor( verts_uvs, cols=2, dtype=torch.float32, device=device ) # (T, 2) faces_verts_idx = _format_faces_indices( faces_verts_idx, verts.shape[0], device=device ) # Repeat for normals and textures if present. if len(faces_normals_idx) > 0: faces_normals_idx = _format_faces_indices( faces_normals_idx, normals.shape[0], device=device, pad_value=-1 ) if len(faces_textures_idx) > 0: faces_textures_idx = _format_faces_indices( faces_textures_idx, verts_uvs.shape[0], device=device, pad_value=-1 ) if len(faces_materials_idx) > 0: faces_materials_idx = torch.tensor( faces_materials_idx, dtype=torch.int64, device=device ) # Load materials material_colors, texture_images, texture_atlas = None, None, None if load_textures: if (len(material_names) > 0) and (f_mtl is not None): # pyre-fixme[6]: Expected `Union[_PathLike[typing.Any], bytes, str]` for # 1st param but got `Optional[str]`. if os.path.isfile(f_mtl): # Texture mode uv wrap material_colors, texture_images = load_mtl( f_mtl, material_names, data_dir, device=device ) if create_texture_atlas: # Using the images and properties from the # material file make a per face texture map. # Create an array of strings of material names for each face. # If faces_materials_idx == -1 then that face doesn't have a material. idx = faces_materials_idx.cpu().numpy() face_material_names = np.array(material_names)[idx] # (F,) face_material_names[idx == -1] = "" # Get the uv coords for each vert in each face faces_verts_uvs = verts_uvs[faces_textures_idx] # (F, 3, 2) # Construct the atlas. texture_atlas = make_mesh_texture_atlas( material_colors, texture_images, face_material_names, faces_verts_uvs, texture_atlas_size, texture_wrap, ) else: warnings.warn(f"Mtl file does not exist: {f_mtl}") elif len(material_names) > 0: warnings.warn("No mtl file provided") faces = _Faces( verts_idx=faces_verts_idx, normals_idx=faces_normals_idx, textures_idx=faces_textures_idx, materials_idx=faces_materials_idx, ) aux = _Aux( normals=normals if len(normals) > 0 else None, verts_uvs=verts_uvs if len(verts_uvs) > 0 else None, material_colors=material_colors, texture_images=texture_images, texture_atlas=texture_atlas, ) return verts, faces, aux def save_obj(f, verts, faces, decimal_places: Optional[int] = None): """ Save a mesh to an .obj file. Args: f: File (or path) to which the mesh should be written. verts: FloatTensor of shape (V, 3) giving vertex coordinates. faces: LongTensor of shape (F, 3) giving faces. decimal_places: Number of decimal places for saving. """ if len(verts) and not (verts.dim() == 2 and verts.size(1) == 3): message = "Argument 'verts' should either be empty or of shape (num_verts, 3)." raise ValueError(message) if len(faces) and not (faces.dim() == 2 and faces.size(1) == 3): message = "Argument 'faces' should either be empty or of shape (num_faces, 3)." raise ValueError(message) f, new_f = _open_file(f, "w") try: return _save(f, verts, faces, decimal_places) finally: if new_f: f.close() # TODO (nikhilar) Speed up this function. def _save(f, verts, faces, decimal_places: Optional[int] = None) -> None: assert not len(verts) or (verts.dim() == 2 and verts.size(1) == 3) assert not len(faces) or (faces.dim() == 2 and faces.size(1) == 3) if not (len(verts) or len(faces)): warnings.warn("Empty 'verts' and 'faces' arguments provided") return verts, faces = verts.cpu(), faces.cpu() lines = "" if len(verts): if decimal_places is None: float_str = "%f" else: float_str = "%" + ".%df" % decimal_places V, D = verts.shape for i in range(V): vert = [float_str % verts[i, j] for j in range(D)] lines += "v %s\n" % " ".join(vert) if torch.any(faces >= verts.shape[0]) or torch.any(faces < 0): warnings.warn("Faces have invalid indices") if len(faces): F, P = faces.shape for i in range(F): face = ["%d" % (faces[i, j] + 1) for j in range(P)] if i + 1 < F: lines += "f %s\n" % " ".join(face) elif i + 1 == F: # No newline at the end of the file. lines += "f %s" % " ".join(face) f.write(lines)