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）。
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// This file is part of gltfpack; see gltfpack.h for version/license details
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#include "gltfpack.h"
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#include <stdlib.h>
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#include <string.h>
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static const char* kMimeTypes[][2] = {
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{"image/jpeg", ".jpg"},
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{"image/jpeg", ".jpeg"},
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{"image/png", ".png"},
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{"image/ktx2", ".ktx2"},
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{"image/webp", ".webp"},
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};
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static const char* inferMimeType(const char* path)
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{
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std::string ext = getExtension(path);
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for (size_t i = 0; i < sizeof(kMimeTypes) / sizeof(kMimeTypes[0]); ++i)
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if (ext == kMimeTypes[i][1])
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return kMimeTypes[i][0];
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return "";
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}
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static bool parseDataUri(const char* uri, std::string& mime_type, std::string& result)
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{
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if (strncmp(uri, "data:", 5) == 0)
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{
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const char* comma = strchr(uri, ',');
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if (comma && comma - uri >= 7 && strncmp(comma - 7, ";base64", 7) == 0)
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{
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const char* base64 = comma + 1;
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size_t base64_size = strlen(base64);
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size_t size = base64_size - base64_size / 4;
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if (base64_size >= 2)
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{
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size -= base64[base64_size - 2] == '=';
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size -= base64[base64_size - 1] == '=';
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}
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void* data = NULL;
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cgltf_options options = {};
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cgltf_result res = cgltf_load_buffer_base64(&options, size, base64, &data);
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if (res != cgltf_result_success)
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return false;
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mime_type = std::string(uri + 5, comma - 7);
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result = std::string(static_cast<const char*>(data), size);
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free(data);
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return true;
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}
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}
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return false;
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}
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static std::string fixupMimeType(const std::string& data, const std::string& mime_type)
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{
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if (mime_type == "image/jpeg" && data.compare(0, 8, "\x89\x50\x4e\x47\x0d\x0a\x1a\x0a") == 0)
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return "image/png";
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if (mime_type == "image/png" && data.compare(0, 3, "\xff\xd8\xff") == 0)
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return "image/jpeg";
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return mime_type;
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}
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bool readImage(const cgltf_image& image, const char* input_path, std::string& data, std::string& mime_type)
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{
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if (image.uri && parseDataUri(image.uri, mime_type, data))
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{
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mime_type = fixupMimeType(data, mime_type);
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return true;
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}
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else if (image.buffer_view && image.buffer_view->buffer->data && image.mime_type)
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{
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const cgltf_buffer_view* view = image.buffer_view;
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data.assign(static_cast<const char*>(view->buffer->data) + view->offset, view->size);
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mime_type = image.mime_type;
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mime_type = fixupMimeType(data, image.mime_type);
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return true;
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}
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else if (image.uri && *image.uri && input_path)
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{
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std::string path = image.uri;
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cgltf_decode_uri(&path[0]);
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path.resize(strlen(&path[0]));
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if (!readFile(getFullPath(path.c_str(), input_path).c_str(), data))
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return false;
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mime_type = image.mime_type ? image.mime_type : inferMimeType(path.c_str());
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mime_type = fixupMimeType(data, mime_type);
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return true;
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}
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else
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{
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return false;
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}
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}
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static int readInt16BE(const std::string& data, size_t offset)
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{
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return (unsigned char)data[offset] * 256 + (unsigned char)data[offset + 1];
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}
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static int readInt32BE(const std::string& data, size_t offset)
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{
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return (unsigned((unsigned char)data[offset]) << 24) |
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(unsigned((unsigned char)data[offset + 1]) << 16) |
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(unsigned((unsigned char)data[offset + 2]) << 8) |
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unsigned((unsigned char)data[offset + 3]);
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}
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static int readInt32LE(const std::string& data, size_t offset)
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{
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return unsigned((unsigned char)data[offset]) |
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(unsigned((unsigned char)data[offset + 1]) << 8) |
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(unsigned((unsigned char)data[offset + 2]) << 16) |
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(unsigned((unsigned char)data[offset + 3]) << 24);
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}
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// https://en.wikipedia.org/wiki/PNG#File_format
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static bool getDimensionsPng(const std::string& data, int& width, int& height)
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{
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if (data.size() < 8 + 8 + 13 + 4)
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return false;
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const char* signature = "\x89\x50\x4e\x47\x0d\x0a\x1a\x0a";
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if (data.compare(0, 8, signature) != 0)
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return false;
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if (data.compare(12, 4, "IHDR") != 0)
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return false;
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width = readInt32BE(data, 16);
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height = readInt32BE(data, 20);
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return true;
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}
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// https://en.wikipedia.org/wiki/JPEG_File_Interchange_Format#File_format_structure
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static bool getDimensionsJpeg(const std::string& data, int& width, int& height)
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{
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size_t offset = 0;
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// note, this can stop parsing before reaching the end but we stop at SOF anyway
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while (offset + 4 <= data.size())
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{
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if (data[offset] != '\xff')
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return false;
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char marker = data[offset + 1];
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if (marker == '\xff')
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{
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offset++;
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continue; // padding
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}
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// d0..d9 correspond to SOI, RSTn, EOI
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if (marker == 0 || unsigned(marker - '\xd0') <= 9)
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{
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offset += 2;
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continue; // no payload
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}
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// c0/c2 correspond to SOF0/SOF2
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if (marker == '\xc0' || marker == '\xc2')
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{
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if (offset + 10 > data.size())
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return false;
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width = readInt16BE(data, offset + 7);
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height = readInt16BE(data, offset + 5);
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return true;
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}
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offset += 2 + readInt16BE(data, offset + 2);
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}
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return false;
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}
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// https://en.wikipedia.org/wiki/PNG#File_format
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static bool hasTransparencyPng(const std::string& data)
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{
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if (data.size() < 8 + 8 + 13 + 4)
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return false;
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const char* signature = "\x89\x50\x4e\x47\x0d\x0a\x1a\x0a";
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if (data.compare(0, 8, signature) != 0)
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return false;
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if (data.compare(12, 4, "IHDR") != 0)
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return false;
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int ctype = data[25];
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if (ctype != 3)
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return ctype == 4 || ctype == 6;
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size_t offset = 8; // reparse IHDR chunk for simplicity
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while (offset + 12 <= data.size())
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{
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int length = readInt32BE(data, offset);
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if (length < 0)
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return false;
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if (data.compare(offset + 4, 4, "tRNS") == 0)
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return true;
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offset += 12 + length;
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}
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return false;
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}
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// https://github.khronos.org/KTX-Specification/ktxspec.v2.html
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static bool hasTransparencyKtx2(const std::string& data)
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{
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if (data.size() < 12 + 17 * 4)
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return false;
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const char* signature = "\xabKTX 20\xbb\r\n\x1a\n";
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if (data.compare(0, 12, signature) != 0)
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return false;
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int dfdOffset = readInt32LE(data, 48);
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int dfdLength = readInt32LE(data, 52);
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if (dfdLength < 4 + 24 + 16 || unsigned(dfdOffset) > data.size() || unsigned(dfdLength) > data.size() - dfdOffset)
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return false;
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const int KDF_DF_MODEL_ETC1S = 163;
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const int KDF_DF_MODEL_UASTC = 166;
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const int KHR_DF_CHANNEL_UASTC_RGBA = 3;
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const int KHR_DF_CHANNEL_ETC1S_RGB = 0;
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const int KHR_DF_CHANNEL_ETC1S_AAA = 15;
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int colorModel = readInt32LE(data, dfdOffset + 12) & 0xff;
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int channelType1 = (readInt32LE(data, dfdOffset + 28) >> 24) & 0xf;
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int channelType2 = dfdLength >= 4 + 24 + 16 * 2 ? (readInt32LE(data, dfdOffset + 44) >> 24) & 0xf : channelType1;
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if (colorModel == KDF_DF_MODEL_ETC1S)
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{
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return channelType1 == KHR_DF_CHANNEL_ETC1S_RGB && channelType2 == KHR_DF_CHANNEL_ETC1S_AAA;
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}
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else if (colorModel == KDF_DF_MODEL_UASTC)
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{
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return channelType1 == KHR_DF_CHANNEL_UASTC_RGBA;
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}
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return false;
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}
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// https://developers.google.com/speed/webp/docs/riff_container
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static bool hasTransparencyWebP(const std::string& data)
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{
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if (data.size() < 12 + 4 + 12)
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return false;
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if (data.compare(0, 4, "RIFF") != 0)
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return false;
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if (data.compare(8, 4, "WEBP") != 0)
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return false;
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// WebP data may use VP8L, VP8X or VP8 format, but VP8 does not support transparency
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if (data.compare(12, 4, "VP8L") == 0)
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{
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if (unsigned(data[20]) != 0x2f)
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return false;
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// width (14) | height (14) | alpha_is_used (1) | version_number(3)
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unsigned int header = readInt32LE(data, 21);
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return (header & (1 << 28)) != 0;
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}
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else if (data.compare(12, 4, "VP8X") == 0)
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{
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// zero (2) | icc (1) | alpha (1) | exif (1) | xmp (1) | animation (1) | zero (1)
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unsigned char header = data[20];
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return (header & (1 << 4)) != 0;
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}
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return false;
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}
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bool hasAlpha(const std::string& data, const char* mime_type)
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{
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if (strcmp(mime_type, "image/png") == 0)
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return hasTransparencyPng(data);
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else if (strcmp(mime_type, "image/ktx2") == 0)
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return hasTransparencyKtx2(data);
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else if (strcmp(mime_type, "image/webp") == 0)
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return hasTransparencyWebP(data);
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else
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return false;
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}
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bool getDimensions(const std::string& data, const char* mime_type, int& width, int& height)
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{
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if (strcmp(mime_type, "image/png") == 0)
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return getDimensionsPng(data, width, height);
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if (strcmp(mime_type, "image/jpeg") == 0)
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return getDimensionsJpeg(data, width, height);
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return false;
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}
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static int roundPow2(int value)
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{
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int result = 1;
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while (result < value)
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result <<= 1;
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// to prevent odd texture sizes from increasing the size too much, we round to nearest power of 2 above a certain size
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if (value > 128 && result * 3 / 4 > value)
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result >>= 1;
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return result;
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}
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static int roundBlock(int value, bool pow2)
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{
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if (value == 0)
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return 4;
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if (pow2 && value > 4)
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return roundPow2(value);
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return (value + 3) & ~3;
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}
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void adjustDimensions(int& width, int& height, float scale, int limit, bool pow2)
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{
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width = int(width * scale);
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height = int(height * scale);
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if (limit && (width > limit || height > limit))
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{
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float limit_scale = float(limit) / float(width > height ? width : height);
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width = int(width * limit_scale);
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height = int(height * limit_scale);
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}
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width = roundBlock(width, pow2);
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height = roundBlock(height, pow2);
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}
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const char* mimeExtension(const char* mime_type)
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{
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for (size_t i = 0; i < sizeof(kMimeTypes) / sizeof(kMimeTypes[0]); ++i)
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if (strcmp(kMimeTypes[i][0], mime_type) == 0)
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return kMimeTypes[i][1];
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return ".raw";
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}
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Block a user