181 lines
6.3 KiB
Python
181 lines
6.3 KiB
Python
import numpy as np
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import sys
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import os
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def compute_vertex_normals(vertices, faces):
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"""
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计算顶点法线
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Args:
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vertices: 顶点列表，每个顶点是[x, y, z]
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faces: 面列表，每个面是顶点索引列表（三角形面为3个索引）
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Returns:
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normals: 顶点法线列表，每个法线是[nx, ny, nz]
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"""
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# 初始化法线数组
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normals = np.zeros_like(vertices, dtype=np.float64)
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# 计算每个面的法线并累加到对应的顶点
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for face in faces:
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if len(face) < 3:
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continue
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# 获取三角形的三个顶点
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v0 = vertices[face[0]]
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v1 = vertices[face[1]]
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v2 = vertices[face[2]]
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# 计算两条边向量
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edge1 = v1 - v0
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edge2 = v2 - v0
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# 计算面法线（叉积）
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face_normal = np.cross(edge1, edge2)
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# 面法线长度（用于加权平均）
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face_area = np.linalg.norm(face_normal)
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# 如果面法线长度不为零，则归一化并加权
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if face_area > 1e-10:
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face_normal_normalized = face_normal / face_area
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# 将面法线累加到每个顶点
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for vertex_index in face:
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normals[vertex_index] += face_normal_normalized
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# 归一化所有顶点法线
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for i in range(len(normals)):
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length = np.linalg.norm(normals[i])
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if length > 1e-10:
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normals[i] /= length
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else:
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# 如果法线长度为零（可能是孤立顶点），设置为默认向上法线
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normals[i] = np.array([0.0, 1.0, 0.0])
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return normals
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def parse_obj_file(filename):
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"""
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解析OBJ文件
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Returns:
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vertices: 顶点列表
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faces: 面索引列表
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has_normals: 是否已经包含法线
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"""
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vertices = []
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faces = []
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existing_normals = []
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has_normals = False
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try:
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with open(filename, 'r', encoding='utf-8') as file:
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for line in file:
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line = line.strip()
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if not line or line.startswith('#'):
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continue
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parts = line.split()
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if not parts:
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continue
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if parts[0] == 'v': # 顶点
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if len(parts) >= 4:
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vertex = [float(parts[1]), float(parts[2]), float(parts[3])]
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vertices.append(vertex)
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elif parts[0] == 'vn': # 法线
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if len(parts) >= 4:
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normal = [float(parts[1]), float(parts[2]), float(parts[3])]
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existing_normals.append(normal)
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has_normals = True
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elif parts[0] == 'f': # 面
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face_vertices = []
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for part in parts[1:]:
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# 处理 f v1/vt1/vn1 v2/vt2/vn2 格式
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vertex_data = part.split('/')
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if vertex_data[0]: # 顶点索引
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# OBJ索引从1开始，转换为从0开始
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vertex_index = int(vertex_data[0]) - 1
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face_vertices.append(vertex_index)
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if len(face_vertices) >= 3:
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# 如果是四边形或多边形，分解为三角形
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for i in range(1, len(face_vertices) - 1):
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faces.append([face_vertices[0], face_vertices[i], face_vertices[i + 1]])
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except UnicodeDecodeError:
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print(f"错误: 无法读取文件 {filename}，请确保文件是UTF-8编码。")
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sys.exit(1)
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return np.array(vertices), faces, has_normals
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def write_obj_file(filename, vertices, faces, normals, original_has_normals=False):
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"""
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写入OBJ文件
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"""
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with open(filename, 'w', encoding='utf-8') as file:
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file.write("# OBJ文件 - 自动计算法线\n")
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file.write(f"# 顶点数: {len(vertices)}\n")
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file.write(f"# 面数: {len(faces)}\n\n")
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# 写入顶点
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# for i, vertex in enumerate(vertices):
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# file.write(f"v {vertex[0]:.6f} {vertex[1]:.6f} {vertex[2]:.6f}\n")
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for i, vertex in enumerate(vertices):
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file.write(f"v {vertex[0]*100:.6f} {vertex[1]*100:.6f} {vertex[2]*100:.6f}\n")
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file.write("\n")
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# 写入法线
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for i, normal in enumerate(normals):
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file.write(f"vn {normal[0]:.6f} {normal[1]:.6f} {normal[2]:.6f}\n")
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file.write("\n")
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# 写入面（使用顶点索引/法线索引格式）
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for face in faces:
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face_line = "f"
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for vertex_index in face:
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# 如果原始文件有法线或者我们计算了法线，使用 v//vn 格式
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face_line += f" {vertex_index + 1}//{vertex_index + 1}"
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file.write(face_line + "\n")
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def process_obj_file(input_file, output_file=None):
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"""
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处理OBJ文件的主要函数
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"""
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if output_file is None:
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base_name = os.path.splitext(input_file)[0]
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output_file = f"{base_name}_with_normals.obj"
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print(f"读取文件: {input_file}")
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vertices, faces, has_normals = parse_obj_file(input_file)
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print(f"找到 {len(vertices)} 个顶点, {len(faces)} 个面")
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if has_normals:
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print("警告: 输入文件已包含法线数据，将被重新计算")
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if len(vertices) == 0:
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print("错误: 没有找到顶点数据")
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return False
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if len(faces) == 0:
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print("错误: 没有找到面数据")
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return False
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print("计算顶点法线中...")
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normals = compute_vertex_normals(vertices, faces)
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print("写入输出文件...")
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write_obj_file(output_file, vertices, faces, normals, has_normals)
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print(f"完成! 输出文件: {output_file}")
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return True
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if __name__ == "__main__":
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input_file = "face.obj" # 默认输入文件
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output_file = "face_with_normals.obj" # 默认输出文件
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process_obj_file(input_file, output_file) |