import torch import torch.nn as nn from pointnet2_lib.pointnet2.pointnet2_modules import PointnetFPModule, PointnetSAModuleMSG from lib.config import cfg def get_model(input_channels=6, use_xyz=True): return Pointnet2MSG(input_channels=input_channels, use_xyz=use_xyz) class Pointnet2MSG(nn.Module): def __init__(self, input_channels=6, use_xyz=True): super().__init__() self.SA_modules = nn.ModuleList() channel_in = input_channels skip_channel_list = [input_channels] for k in range(cfg.RPN.SA_CONFIG.NPOINTS.__len__()): mlps = cfg.RPN.SA_CONFIG.MLPS[k].copy() channel_out = 0 for idx in range(mlps.__len__()): mlps[idx] = [channel_in] + mlps[idx] channel_out += mlps[idx][-1] self.SA_modules.append( PointnetSAModuleMSG( npoint=cfg.RPN.SA_CONFIG.NPOINTS[k], radii=cfg.RPN.SA_CONFIG.RADIUS[k], nsamples=cfg.RPN.SA_CONFIG.NSAMPLE[k], mlps=mlps, use_xyz=use_xyz, bn=cfg.RPN.USE_BN ) ) skip_channel_list.append(channel_out) channel_in = channel_out self.FP_modules = nn.ModuleList() for k in range(cfg.RPN.FP_MLPS.__len__()): pre_channel = cfg.RPN.FP_MLPS[k + 1][-1] if k + 1 < len(cfg.RPN.FP_MLPS) else channel_out self.FP_modules.append( PointnetFPModule(mlp=[pre_channel + skip_channel_list[k]] + cfg.RPN.FP_MLPS[k]) ) def _break_up_pc(self, pc): xyz = pc[..., 0:3].contiguous() features = ( pc[..., 3:].transpose(1, 2).contiguous() if pc.size(-1) > 3 else None ) return xyz, features def forward(self, pointcloud: torch.cuda.FloatTensor): xyz, features = self._break_up_pc(pointcloud) l_xyz, l_features = [xyz], [features] for i in range(len(self.SA_modules)): li_xyz, li_features = self.SA_modules[i](l_xyz[i], l_features[i]) l_xyz.append(li_xyz) l_features.append(li_features) for i in range(-1, -(len(self.FP_modules) + 1), -1): l_features[i - 1] = self.FP_modules[i]( l_xyz[i - 1], l_xyz[i], l_features[i - 1], l_features[i] ) return l_xyz[0], l_features[0]中的self.SA_modules.append( PointnetSAModuleMSG( npoint=cfg.RPN.SA_CONFIG.NPOINTS[k], radii=cfg.RPN.SA_CONFIG.RADIUS[k], nsamples=cfg.RPN.SA_CONFIG.NSAMPLE[k], mlps=mlps, use_xyz=use_xyz, bn=cfg.RPN.USE_BN ) )是什么含义和作用

这段代码定义了一个PointNet++网络的模型，其中SA_modules是一系列的PointnetSAModuleMSG模块，每个模块的作用是对输入的点云进行分组、采样、卷积和池化操作。FP_modules是一系列的PointnetFPModule模块，每个模块的作用是对上一层的特征进行上采样和卷积操作，最后输出整个网络的特征。其中，PointnetSAModuleMSG和PointnetFPModule是PointNet++网络中的两种核心模块。具体地，PointnetSAModuleMSG用于处理不同密度的点云，而PointnetFPModule用于特征融合和特征提取。在SA_modules中，PointnetSAModuleMSG通过npoint、radii、nsamples和mlps等参数来定义不同的分组、采样和卷积操作，以逐步提取点云的局部特征。在FP_modules中，PointnetFPModule通过mlp参数来定义上采样和卷积操作，以将不同层次的特征进行融合。