trellis2/utils/mesh_utils.py

from typing import Tuple, Dict
import numpy as np
from trimesh import grouping, util, remesh
import struct
import re
from plyfile import PlyData, PlyElement


def read_ply(filename):
    """
    Read a PLY file and return vertices, triangle faces, and quad faces.
    
    Args:
        filename (str): The file path to read from.
        
    Returns:
        vertices (np.ndarray): Array of shape [N, 3] containing vertex positions.
        tris (np.ndarray): Array of shape [M, 3] containing triangle face indices (empty if none).
        quads (np.ndarray): Array of shape [K, 4] containing quad face indices (empty if none).
    """
    with open(filename, 'rb') as f:
        # Read the header until 'end_header' is encountered
        header_bytes = b""
        while True:
            line = f.readline()
            if not line:
                raise ValueError("PLY header not found")
            header_bytes += line
            if b"end_header" in line:
                break
        header = header_bytes.decode('utf-8')
        
        # Determine if the file is in ASCII or binary format
        is_ascii = "ascii" in header
        
        # Extract the number of vertices and faces from the header using regex
        vertex_match = re.search(r'element vertex (\d+)', header)
        if vertex_match:
            num_vertices = int(vertex_match.group(1))
        else:
            raise ValueError("Vertex count not found in header")
            
        face_match = re.search(r'element face (\d+)', header)
        if face_match:
            num_faces = int(face_match.group(1))
        else:
            raise ValueError("Face count not found in header")
        
        vertices = []
        tris = []
        quads = []
        
        if is_ascii:
            # For ASCII format, read each line of vertex data (each line contains 3 floats)
            for _ in range(num_vertices):
                line = f.readline().decode('utf-8').strip()
                if not line: 
                    continue
                parts = line.split()
                vertices.append([float(parts[0]), float(parts[1]), float(parts[2])])
            
            # Read face data, where the first number indicates the number of vertices for the face
            for _ in range(num_faces):
                line = f.readline().decode('utf-8').strip()
                if not line: 
                    continue
                parts = line.split()
                count = int(parts[0])
                indices = list(map(int, parts[1:]))
                if count == 3:
                    tris.append(indices)
                elif count == 4:
                    quads.append(indices)
                else:
                    # Skip faces with other numbers of vertices (can be extended as needed)
                    pass
        else:
            # For binary format: read directly from the binary stream
            # Each vertex consists of 3 floats (12 bytes per vertex)
            for _ in range(num_vertices):
                data = f.read(12)
                if len(data) < 12:
                    raise ValueError("Insufficient vertex data")
                v = struct.unpack('<fff', data)
                vertices.append(v)
            
            # Read face data from the binary stream
            for _ in range(num_faces):
                # First, read 1 byte indicating the number of vertices in the face
                count_data = f.read(1)
                if len(count_data) < 1:
                    raise ValueError("Failed to read face vertex count")
                count = struct.unpack('<B', count_data)[0]
                if count == 3:
                    data = f.read(12)  # 3 * 4 bytes
                    if len(data) < 12:
                        raise ValueError("Insufficient data for triangle face")
                    indices = struct.unpack('<3i', data)
                    tris.append(indices)
                elif count == 4:
                    data = f.read(16)  # 4 * 4 bytes
                    if len(data) < 16:
                        raise ValueError("Insufficient data for quad face")
                    indices = struct.unpack('<4i', data)
                    quads.append(indices)
                else:
                    # For faces with a different number of vertices, read count*4 bytes
                    data = f.read(count * 4)
                    # Skip or extend processing as needed
                    raise ValueError(f"Unsupported face with {count} vertices")
        
        # Convert lists to torch.Tensor
        vertices = np.array(vertices, dtype=np.float32)
        tris = np.array(tris, dtype=np.int32) if len(tris) > 0 else np.empty((0, 3), dtype=np.int32)
        quads = np.array(quads, dtype=np.int32) if len(quads) > 0 else np.empty((0, 4), dtype=np.int32)
        
        return vertices, tris, quads


def write_ply(
    filename: str,
    vertices: np.ndarray,
    tris: np.ndarray,
    quads: np.ndarray,
    vertex_colors: np.ndarray = None,
    ascii: bool = False
):
    """
    Write a mesh to a PLY file, with the option to save in ASCII or binary format,
    and optional per-vertex colors.
    
    Args:
        filename (str): The filename to write to.
        vertices (np.ndarray): [N, 3] The vertex positions.
        tris (np.ndarray): [M, 3] The triangle indices.
        quads (np.ndarray): [K, 4] The quad indices.
        vertex_colors (np.ndarray, optional): [N, 3] or [N, 4] UInt8 colors for each vertex (RGB or RGBA).
        ascii (bool): If True, write in ASCII format; otherwise binary little-endian.
    """
    import struct

    num_vertices = len(vertices)
    num_faces = len(tris) + len(quads)

    # Build header
    header_lines = [
        "ply",
        f"format {'ascii 1.0' if ascii else 'binary_little_endian 1.0'}",
        f"element vertex {num_vertices}",
        "property float x",
        "property float y",
        "property float z",
    ]

    # Add vertex color properties if provided
    has_color = vertex_colors is not None
    if has_color:
        # Expect uint8 values 0-255
        header_lines += [
            "property uchar red",
            "property uchar green",
            "property uchar blue",
        ]
        # Include alpha if RGBA
        if vertex_colors.shape[1] == 4:
            header_lines.append("property uchar alpha")

    header_lines += [
        f"element face {num_faces}",
        "property list uchar int vertex_index",
        "end_header",
        ""
    ]
    header = "\n".join(header_lines)

    mode = 'w' if ascii else 'wb'
    with open(filename, mode) as f:
        # Write header
        if ascii:
            f.write(header)
        else:
            f.write(header.encode('utf-8'))

        # Write vertex data
        for i, v in enumerate(vertices):
            if ascii:
                line = f"{v[0]} {v[1]} {v[2]}"
                if has_color:
                    col = vertex_colors[i]
                    line += ' ' + ' '.join(str(int(c)) for c in col)
                f.write(line + '\n')
            else:
                # pack xyz as floats
                f.write(struct.pack('<fff', *v))
                if has_color:
                    col = vertex_colors[i]
                    # pack as uchar
                    if col.shape[0] == 3:
                        f.write(struct.pack('<BBB', *col))
                    else:
                        f.write(struct.pack('<BBBB', *col))

        # Write face data
        if ascii:
            for tri in tris:
                f.write(f"3 {tri[0]} {tri[1]} {tri[2]}\n")
            for quad in quads:
                f.write(f"4 {quad[0]} {quad[1]} {quad[2]} {quad[3]}\n")
        else:
            for tri in tris:
                f.write(struct.pack('<B3i', 3, *tri))
            for quad in quads:
                f.write(struct.pack('<B4i', 4, *quad))
                

def write_pbr_ply(
    filename: str,
    vertices: np.ndarray,
    faces: np.ndarray,
    base_color: np.ndarray,
    metallic: np.ndarray,
    roughness: np.ndarray,
    alpha: np.ndarray,
    ascii: bool = False
):
    """
    Write a mesh to a PLY file, with the option to save in ASCII or binary format,
    and optional per-vertex colors.
    
    Args:
        filename (str): The filename to write to.
        vertices (np.ndarray): [N, 3] The vertex positions.
        faces (np.ndarray): [M, 3] The triangle indices.
        base_color (np.ndarray): [N, 3] UInt8 colors for each vertex (RGB).
        metallic (np.ndarray): [N] UInt8 values for metallicness.
        roughness (np.ndarray): [N] UInt8 values for roughness.
        alpha (np.ndarray): [N] UInt8 values for alpha.
        ascii (bool): If True, write in ASCII format; otherwise binary little-endian.
    """
    vertex_dtype = [
        ('x', 'f4'), ('y', 'f4'), ('z', 'f4'),
        ('red', 'u1'), ('green', 'u1'), ('blue', 'u1'),
        ('metallic', 'u1'), ('roughness', 'u1'), ('alpha', 'u1')
    ]
    
    vertex_data = np.empty(len(vertices), dtype=vertex_dtype)
    vertex_data['x'] = vertices[:, 0]
    vertex_data['y'] = vertices[:, 1]
    vertex_data['z'] = vertices[:, 2]
    vertex_data['red'] = base_color[:, 0]
    vertex_data['green'] = base_color[:, 1]
    vertex_data['blue'] = base_color[:, 2]
    vertex_data['metallic'] = metallic
    vertex_data['roughness'] = roughness
    vertex_data['alpha'] = alpha
    
    face_dtype = [
        ('vertex_indices', 'i4', (3,))
    ]
    
    face_data = np.empty(len(faces), dtype=face_dtype)
    face_data['vertex_indices'] = faces
    
    ply_data = PlyData([
        PlyElement.describe(vertex_data,'vertex'),
        PlyElement.describe(face_data, 'face'),
    ], text=ascii)
    ply_data.write(filename)