ModelTranslator: sphere-map normal encode with round-trip test

2026-07-15 11:06:16 +08:00
parent e8b3425db4
commit 7934ef957a
2 changed files with 66 additions and 0 deletions
@@ -0,0 +1,23 @@
+"""Blender 内运行：FBX -> 纯模型 FBX + XPbr 基础/混合贴图。
+调用：blender -b --factory-startup --python bl_convert.py -- <src.fbx> <outdir> <max_size>
+"""
+import numpy as np
+
+
+def encode_normal_rg(n):
+    """切线法线 (N,3) -> 球面编码 (N,2)，范围 [0,1]。
+    shader 侧 XPbr_Base.hlsl DecodeSphereMap 先 *2-1 再解码。"""
+    n = n / np.maximum(np.linalg.norm(n, axis=-1, keepdims=True), 1e-8)
+    z = np.clip(n[..., 2], -0.99, 1.0)
+    denom = np.sqrt(2.0 * (1.0 + z))
+    enc = n[..., :2] / denom[..., None]
+    return np.clip(enc * 0.5 + 0.5, 0.0, 1.0)
+
+
+def decode_sphere_map(enc01):
+    """shader DecodeSphereMap 的 numpy 等价（含 *2-1），仅测试用。"""
+    e = enc01 * 2.0 - 1.0
+    l = 1.0 - e[..., 0] ** 2 - e[..., 1] ** 2
+    l = np.clip(l, 0.0, 1.0)
+    xy = e * np.sqrt(l)[..., None]
+    return np.concatenate([xy * 2.0, (l * 2.0 - 1.0)[..., None]], axis=-1)