1 图像对齐
std::for_each(ref_frame->seg_fts_.begin(), ref_frame->seg_fts_.end(), [&](plsvo::Feature* i){
LineFeat* seg = static_cast<LineFeat*>(i);
total_length += seg->length;
});
计算一帧线特征的累积长度
int max_num_seg_samples = std::ceil( total_length / patch_size_ );
计算得到线特征的最大数量
设置缓存结构以分配优化数据(残留物,jacobians等)