feat: LOD 网格分级——meshopt 解析期简化 + 按距离/级联选级

vendored meshoptimizer 1.2（submodule 环境故障改直接 vendor）。Mesh 多 LOD：各级索引连续拼进同一 index buffer（共享顶点，LodRange 区间选择），解析期 meshopt_simplify 生成链（LOD0=原始，每级目标减半，相对误差 1e-2，小网格复用上级）；都在 worker 线程，加载零额外卡顿。 SceneRenderer 按 (mesh, LOD) 聚合 batch（lookup key = 指针<<8|lod）：主视图按屏占比近似 radius/dist 选级（阈值 10/20 倍半径）；阴影级联按级联序降级（越远越简）。Draw 按 batch.lod 选索引区间。 A/B 对比（100 背包 10×10，RTX 5060 Laptop，vsync off）： - 纯背包：LOD 开 93-95 fps / 关 90-107 fps —— 无显著差异 - 加 SunTemple：LOD 开 52-56 / 关 51-55 —— 无显著差异结论：当前场景瓶颈不在顶点数（5060 顶点吞吐富余），LOD 基础设施保留（几何复杂资产/低端 GPU/更大场景生效），帧率问题转向 Tracy GPU 时间线定位真实瓶颈。坑：LodRange 记录"LOD 不足复用最后一级"时 first 不得继续累加（buffer 无重复数据，累加必越界——VUID-08798 抓的）。
2026-09-24 20:53:19 +08:00
parent 34b593f734
commit 5bdfb53566
125 changed files with 67608 additions and 29 deletions
@@ -0,0 +1,61 @@
+#include "../src/meshoptimizer.h"
+
+#include <float.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* buffer, size_t size)
+{
+	if (size == 0)
+		return 0;
+
+	srand(buffer[0]);
+
+	float vb[100][4];
+
+	for (int i = 0; i < 100; ++i)
+	{
+		vb[i][0] = rand() % 10;
+		vb[i][1] = rand() % 10;
+		vb[i][2] = rand() % 10;
+		vb[i][3] = rand() % 10;
+	}
+
+	unsigned int ib[999];
+	int indices = (size - 1) < 999 ? (size - 1) / 3 * 3 : 999;
+
+	for (int i = 0; i < indices; ++i)
+		ib[i] = buffer[1 + i] % 100;
+
+	meshopt_Meshlet ml[333];
+	unsigned int mv[333 * 3];
+	unsigned char mt[333 * 4];
+
+	meshopt_buildMeshlets(ml, mv, mt, ib, indices, vb[0], 100, sizeof(float) * 4, /* max_vertices= */ 4, /* max_triangles= */ 4, 0.f);
+
+	meshopt_buildMeshletsScan(ml, mv, mt, ib, indices, 100, /* max_vertices= */ 4, /* max_triangles= */ 4);
+	meshopt_buildMeshletsScan(ml, mv, mt, ib, indices, 100, /* max_vertices= */ 4, /* max_triangles= */ 8);
+
+	meshopt_buildMeshletsFlex(ml, mv, mt, ib, indices, vb[0], 100, sizeof(float) * 4, /* max_vertices= */ 4, /* min_triangles= */ 4, /* max_triangles= */ 8, 0.f, 2.f);
+	meshopt_buildMeshletsFlex(ml, mv, mt, ib, indices, vb[0], 100, sizeof(float) * 4, /* max_vertices= */ 8, /* min_triangles= */ 8, /* max_triangles= */ 16, 0.f, 2.f);
+	meshopt_buildMeshletsFlex(ml, mv, mt, ib, indices, vb[0], 100, sizeof(float) * 4, /* max_vertices= */ 16, /* min_triangles= */ 8, /* max_triangles= */ 32, 0.f, 2.f);
+	meshopt_buildMeshletsFlex(ml, mv, mt, ib, indices, vb[0], 100, sizeof(float) * 4, /* max_vertices= */ 16, /* min_triangles= */ 16, /* max_triangles= */ 32, 0.f, 2.f);
+
+	meshopt_buildMeshletsSpatial(ml, mv, mt, ib, indices, vb[0], 100, sizeof(float) * 4, /* max_vertices= */ 4, /* min_triangles= */ 4, /* max_triangles= */ 8, 0.f);
+	meshopt_buildMeshletsSpatial(ml, mv, mt, ib, indices, vb[0], 100, sizeof(float) * 4, /* max_vertices= */ 8, /* min_triangles= */ 4, /* max_triangles= */ 32, 0.f);
+	meshopt_buildMeshletsSpatial(ml, mv, mt, ib, indices, vb[0], 100, sizeof(float) * 4, /* max_vertices= */ 8, /* min_triangles= */ 8, /* max_triangles= */ 32, 0.f);
+	meshopt_buildMeshletsSpatial(ml, mv, mt, ib, indices, vb[0], 100, sizeof(float) * 4, /* max_vertices= */ 8, /* min_triangles= */ 12, /* max_triangles= */ 32, 0.f);
+	meshopt_buildMeshletsSpatial(ml, mv, mt, ib, indices, vb[0], 100, sizeof(float) * 4, /* max_vertices= */ 16, /* min_triangles= */ 16, /* max_triangles= */ 32, 0.f);
+	meshopt_buildMeshletsSpatial(ml, mv, mt, ib, indices, vb[0], 100, sizeof(float) * 4, /* max_vertices= */ 16, /* min_triangles= */ 32, /* max_triangles= */ 32, 0.f);
+
+	unsigned int part[333];
+	unsigned int clsize[333];
+
+	// treat each triangle as a cluster
+	for (int i = 0; i < indices; ++i)
+		clsize[i / 3] = 3;
+
+	meshopt_partitionClusters(part, ib, indices, clsize, indices / 3, vb[0], 100, sizeof(float) * 4, /* target_group_size= */ 12);
+
+	return 0;
+}