draco 解压

参照google源码中的示例draco_decoder,draco_encoder基本大概可以了解到Draco的使用逻辑：

#include <core/decoder_buffer.h>
#include <io/mesh_io.h>

#include <fstream>
#include <iostream>

using namespace draco;
using namespace std;

int main() {
  string filePath = "D:/1.bin";

  ifstream infile(filePath, ios::binary);

  infile.seekg(0, std::ios::end);
  size_t data_size = infile.tellg();

  infile.seekg(0, std::ios::beg);

  vector<char> data(data_size, 0);
  infile.read(data.data(), data_size);

  DecoderBuffer buffer;
  buffer.Init(data.data(), data_size);

  //解压缩
  std::unique_ptr<draco::PointCloud> pc;
  auto type_statusor = draco::Decoder::GetEncodedGeometryType(&buffer);
  if (!type_statusor.ok()) {
    return 1;
  }

  //解析数据
  const draco::EncodedGeometryType geom_type = type_statusor.value();
  if (geom_type == draco::TRIANGULAR_MESH) {
    draco::Decoder decoder;
    auto statusor = decoder.DecodeMeshFromBuffer(&buffer);
    if (!statusor.ok()) {
      return 1;
    }
    std::unique_ptr<draco::Mesh> mesh = std::move(statusor).value();
    if (mesh) {
      const int pos_att_id =
          mesh->GetNamedAttributeId(GeometryAttribute::POSITION);

      //解析顶点属性
      for (PointIndex v(0); v < mesh->num_points(); ++v) {
        const auto *const pos_att = mesh->attribute(pos_att_id);

        const uint8_t *pos = pos_att->GetAddress(pos_att->mapped_index(v));
        int64_t length = pos_att->byte_stride();
        float temp[3];
        memcpy(temp, pos, length);
        printf("%f,%f,%f\t", temp[0], temp[1], temp[2]);
      }

      //解析顶点索引
      for (FaceIndex f(0); f < mesh->num_faces(); ++f) {
        printf("%d,%d,%d\t", mesh->face(f)[0].value(), mesh->face(f)[1].value(),
               mesh->face(f)[2].value());
      }
    }
  }
}