76 lines
2.8 KiB
Python
76 lines
2.8 KiB
Python
"""
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解析 face_picture_3dmax.obj，得到顶点 UV 和三角形索引。
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OBJ 约定：v 顶点 / vt UV / vn 法线，f 三元组 v/vt/vn 索引（1-based）。
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本服务只需要每个顶点的 UV 和三角形顶点索引——3D 顶点位置在 SDK 里也只是
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占位（运行时被 MediaPipe landmark 覆盖），这里同样无需读 v。
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★ 与 vulkan/FaceApp.cpp::LoadOBJ 一致，UV 的 V 分量取 (1 - v)，把 OBJ 的
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bottom-up 约定翻成 top-down，与图像（OpenCV/Pillow）一致。
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"""
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from dataclasses import dataclass
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from pathlib import Path
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import numpy as np
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@dataclass
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class FaceMesh:
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# (468, 2) float32, 每个顶点的 UV，V 已翻转，∈ [0,1]²
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uvs: np.ndarray
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# (852, 3) int32, 每个三角形的 3 个顶点索引（0-based，指向 uvs 第一维）
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triangles: np.ndarray
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def load_face_mesh(obj_path: str | Path) -> FaceMesh:
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obj_path = Path(obj_path)
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text = obj_path.read_text(encoding="utf-8", errors="ignore")
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pos_count = 0
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uv_list: list[tuple[float, float]] = []
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# OBJ 的 face 用 v/vt/vn，三个索引可能不同；但本工程的 obj 三者一一对齐
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# （pos_index == uv_index == normal_index），所以我们只看 v 索引来索引 UV
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# 列表也成立。这里仍然显式校验以防换 obj 时出错。
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triangles: list[tuple[int, int, int]] = []
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for raw in text.splitlines():
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line = raw.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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tag = parts[0]
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if tag == "v":
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pos_count += 1
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elif tag == "vt":
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u = float(parts[1])
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v = float(parts[2])
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uv_list.append((u, 1.0 - v)) # V 翻转
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elif tag == "f":
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if len(parts) != 4:
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raise ValueError(f"only triangle faces supported, got: {line}")
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tri: list[int] = []
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for token in parts[1:]:
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# 形如 "v/vt/vn" 或 "v//vn" 或 "v"
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seg = token.split("/")
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v_idx = int(seg[0]) - 1 # OBJ 1-based → 0-based
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vt_idx = int(seg[1]) - 1 if len(seg) > 1 and seg[1] else v_idx
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if v_idx != vt_idx:
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raise ValueError(
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f"this loader assumes pos_idx == uv_idx, "
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f"got v={v_idx + 1} vt={vt_idx + 1} in line: {line}"
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)
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tri.append(v_idx)
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triangles.append((tri[0], tri[1], tri[2]))
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if pos_count != len(uv_list):
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raise ValueError(
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f"vertex count {pos_count} != uv count {len(uv_list)}; "
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"obj loader assumes 1:1 correspondence"
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)
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uvs = np.asarray(uv_list, dtype=np.float32)
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tris = np.asarray(triangles, dtype=np.int32)
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return FaceMesh(uvs=uvs, triangles=tris)
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