267 lines
9.3 KiB
Python
267 lines
9.3 KiB
Python
"""Blender 内运行：FBX 减面到指定三角面数 + UV 重展（锐边 seam 或 Smart UV Project）。
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调用：blender -b --factory-startup --python bl_decimate.py -- <src.fbx> <out.fbx> <target_tris> [seam|smart]
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"""
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import os
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import sys
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sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
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TOLERANCE = 0.03 # 面数相对误差容忍
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MAX_RETRY = 2 # ratio 修正轮数上限
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def decimate_ratio(target, cur):
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"""Decimate collapse ratio；cur <= target 或非法时返回 1.0（不减面）。"""
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if cur <= 0 or cur <= target:
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return 1.0
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return target / float(cur)
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def within_tolerance(target, actual, tol=TOLERANCE):
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"""减面结果是否落在目标 ±tol 内。"""
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if target <= 0:
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return False
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return abs(actual - target) <= target * tol
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UV_BAD_TOL = 0.02 # 质量门：UV 翻转/重叠面占比超此值则回退 smart_project
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def count_islands(n_faces, adjacent_pairs):
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"""union-find 数 UV 岛：n_faces 个面，adjacent_pairs 为 UV 连续的面索引对。"""
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parent = list(range(n_faces))
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def find(i):
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while parent[i] != i:
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parent[i] = parent[parent[i]]
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i = parent[i]
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return i
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for a, b in adjacent_pairs:
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ra, rb = find(a), find(b)
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if ra != rb:
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parent[ra] = rb
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return len({find(i) for i in range(n_faces)})
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def flipped_fraction(signed_areas):
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"""UV 面签名面积为负（翻转）的占比。"""
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if not signed_areas:
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return 0.0
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return sum(1 for a in signed_areas if a < 0) / float(len(signed_areas))
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def fill_ratio(abs_areas):
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"""UV 空间利用率：面积和（重叠会虚高，截断到 1.0）。"""
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return min(1.0, sum(abs_areas))
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# ---------------- 以下仅在 Blender 内执行 ----------------
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def join_meshes(objs):
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"""多 mesh join 成单对象，返回结果对象（bl_bake 复用）。"""
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import bpy
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bpy.ops.object.select_all(action='DESELECT')
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for o in objs:
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o.select_set(True)
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bpy.context.view_layer.objects.active = objs[0]
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if len(objs) > 1:
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bpy.ops.object.join()
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return bpy.context.view_layer.objects.active
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def _apply_modifier(obj, mod):
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import bpy
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bpy.context.view_layer.objects.active = obj
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bpy.ops.object.modifier_apply(modifier=mod.name)
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def _triangulate(obj):
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mod = obj.modifiers.new("mt_tri", 'TRIANGULATE')
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_apply_modifier(obj, mod)
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def _decimate(obj, ratio):
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mod = obj.modifiers.new("mt_dec", 'DECIMATE')
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mod.decimate_type = 'COLLAPSE'
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mod.ratio = ratio
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mod.use_collapse_triangulate = True
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_apply_modifier(obj, mod)
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SEAM_ANGLE_DEG = 66.0 # 锐边阈值：两面夹角超此值标 seam
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PACK_MARGIN = 0.002 # 岛间距 ≈ 2048 图 4px
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def _clear_uv_layers(mesh):
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while mesh.uv_layers:
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mesh.uv_layers.remove(mesh.uv_layers[0])
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def _unwrap_smart(obj):
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"""Smart UV Project（原路径，也是质量门的回退路径）。"""
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import bpy
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import math
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_clear_uv_layers(obj.data)
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bpy.context.view_layer.objects.active = obj
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bpy.ops.object.mode_set(mode='EDIT')
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bpy.ops.mesh.select_all(action='SELECT')
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bpy.ops.uv.smart_project(angle_limit=math.radians(66.0), island_margin=PACK_MARGIN)
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bpy.ops.object.mode_set(mode='OBJECT')
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def _unwrap_seam(obj, warnings):
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"""锐边标 seam -> MINIMUM_STRETCH/ANGLE_BASED 展开 -> pack。碎岛远少于投影式。"""
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import bpy
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import math
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_clear_uv_layers(obj.data)
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obj.data.uv_layers.new()
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bpy.context.view_layer.objects.active = obj
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bpy.ops.object.mode_set(mode='EDIT')
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# 锐边标 seam：接缝只落在硬边处，平滑区域保持整岛
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bpy.ops.mesh.select_mode(type='EDGE')
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bpy.ops.mesh.select_all(action='DESELECT')
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bpy.ops.mesh.edges_select_sharp(sharpness=math.radians(SEAM_ANGLE_DEG))
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bpy.ops.mesh.mark_seam(clear=False)
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bpy.ops.mesh.select_all(action='SELECT')
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try:
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bpy.ops.uv.unwrap(method='MINIMUM_STRETCH', margin=PACK_MARGIN)
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except TypeError: # 老版本无 SLIM 枚举
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warnings.append("MINIMUM_STRETCH 不可用，展开改用 ANGLE_BASED")
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bpy.ops.uv.unwrap(method='ANGLE_BASED', margin=PACK_MARGIN)
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try:
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bpy.ops.uv.pack_islands(rotate=True, margin=PACK_MARGIN)
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except RuntimeError: # headless 上下文不满足时靠 unwrap 自带打包
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warnings.append("pack_islands 不可用，沿用 unwrap 自带布局")
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bpy.ops.object.mode_set(mode='OBJECT')
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def _collect_uv_metrics(obj):
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"""bmesh 提取 UV 指标：岛数（UV 连续边并查集）、利用率、翻转占比、重叠占比。"""
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import bmesh
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bm = bmesh.new()
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bm.from_mesh(obj.data)
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uv = bm.loops.layers.uv.active
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pairs = []
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for e in bm.edges:
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if len(e.link_faces) != 2:
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continue
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f1, f2 = e.link_faces
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cont = True
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for v in e.verts: # 两面在该边两端 UV 一致 => UV 连续（同岛）
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l1 = next(l for l in f1.loops if l.vert == v)
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l2 = next(l for l in f2.loops if l.vert == v)
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if (l1[uv].uv - l2[uv].uv).length > 1e-6:
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cont = False
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break
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if cont:
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pairs.append((f1.index, f2.index))
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signed = []
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for f in bm.faces:
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area = 0.0
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loops = f.loops
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for i in range(len(loops)):
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a = loops[i][uv].uv
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b = loops[(i + 1) % len(loops)][uv].uv
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area += a.x * b.y - b.x * a.y
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signed.append(area * 0.5)
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n = len(bm.faces)
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bm.free()
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return {"islands": count_islands(n, pairs),
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"fill": round(fill_ratio([abs(a) for a in signed]), 4),
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"flipped": round(flipped_fraction(signed), 4),
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"overlap": _overlap_fraction(obj)}
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def _overlap_fraction(obj):
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"""uv.select_overlap 统计重叠 UV 面占比；op 上下文不可用返回 None。"""
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import bpy
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bpy.context.scene.tool_settings.use_uv_select_sync = True
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bpy.context.view_layer.objects.active = obj
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bpy.ops.object.mode_set(mode='EDIT')
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bpy.ops.mesh.select_all(action='DESELECT')
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try:
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bpy.ops.uv.select_overlap()
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except RuntimeError:
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return None
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finally:
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bpy.ops.object.mode_set(mode='OBJECT')
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polys = obj.data.polygons
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if not len(polys):
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return 0.0
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return round(sum(1 for p in polys if p.select) / float(len(polys)), 4)
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def _do_unwrap(obj, mode, warnings):
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"""按模式展开；seam 质量不达标自动回退 smart。返回 uv 指标 dict（含 mode）。"""
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if mode == "seam":
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_unwrap_seam(obj, warnings)
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m = _collect_uv_metrics(obj)
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overlap = m["overlap"] or 0.0
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if m["flipped"] <= UV_BAD_TOL and overlap <= UV_BAD_TOL:
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m["mode"] = "seam"
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return m
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warnings.append("seam 展开质量不达标（翻转 %.1f%% 重叠 %s），回退 smart_project"
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% (m["flipped"] * 100,
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"%.1f%%" % (m["overlap"] * 100) if m["overlap"] is not None else "未知"))
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mode = "smart_fallback"
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_unwrap_smart(obj)
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m = _collect_uv_metrics(obj)
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m["mode"] = mode if mode == "smart_fallback" else "smart"
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return m
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def main():
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import bpy
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import json
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argv = sys.argv[sys.argv.index("--") + 1:]
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src, out_fbx, target = argv[0], argv[1], int(argv[2])
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unwrap_mode = argv[3] if len(argv) > 3 else "seam"
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warnings = []
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bpy.ops.wm.read_factory_settings(use_empty=True)
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bpy.ops.import_scene.fbx(filepath=src)
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meshes = [o for o in bpy.data.objects if o.type == 'MESH']
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skipped = [o.name for o in bpy.data.objects if o.type != 'MESH']
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if skipped:
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warnings.append("忽略非 mesh 对象：%s（本工具只处理静态网格）" % ", ".join(skipped))
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if not meshes:
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print("MT_SUMMARY " + json.dumps({"error": "FBX 中没有 mesh"}, ensure_ascii=False))
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return
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obj = join_meshes(meshes)
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_triangulate(obj)
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orig = len(obj.data.polygons)
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cur = orig
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if cur <= target:
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warnings.append("当前 %d 面 <= 目标 %d，跳过减面" % (cur, target))
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else:
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# collapse 结果是近似值；未达容差时按新面数修正 ratio 再来，最多 MAX_RETRY 轮
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for _ in range(1 + MAX_RETRY):
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_decimate(obj, decimate_ratio(target, cur))
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_triangulate(obj) # collapse triangulate 后仍可能残留非三角面
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cur = len(obj.data.polygons)
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if within_tolerance(target, cur) or cur <= target:
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break
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# 重试用尽仍超差且偏多：记录警告，交由上层决定是否可接受
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if not within_tolerance(target, cur) and cur > target:
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warnings.append("修正 %d 轮后仍超差：%d 面（目标 %d ±3%%）" % (MAX_RETRY, cur, target))
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uv_info = _do_unwrap(obj, unwrap_mode, warnings)
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out_dir = os.path.dirname(os.path.abspath(out_fbx))
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os.makedirs(out_dir, exist_ok=True)
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# 仅导出合并后的对象；整场景导出会把 armature/empty 等非 mesh 带进 _low.fbx
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bpy.ops.export_scene.fbx(filepath=out_fbx, use_selection=True,
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path_mode='STRIP', embed_textures=False)
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print("MT_SUMMARY " + json.dumps(
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{"src": os.path.basename(src), "fbx": os.path.basename(out_fbx),
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"tris_before": orig, "tris_after": cur, "target": target,
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"uv": uv_info, "warnings": warnings}, ensure_ascii=False))
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if __name__ == "__main__" and "--" in sys.argv:
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main()
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