model.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
@Author: Yue Wang
@Contact: yuewangx@mit.edu
@File: model.py
@Time: 2018/10/13 6:35 PM

Modified by 
@Author: An Tao, Ziyi Wu
@Contact: ta19@mails.tsinghua.edu.cn, dazitu616@gmail.com
@Time: 2022/7/30 7:49 PM
"""


import os
import sys
import copy
import math
import numpy as np
import torch
import torch.nn as nn
import torch.nn.init as init
import torch.nn.functional as F


def knn(x, k):
    inner = -2*torch.matmul(x.transpose(2, 1), x)
    xx = torch.sum(x**2, dim=1, keepdim=True)
    pairwise_distance = -xx - inner - xx.transpose(2, 1)
 
    idx = pairwise_distance.topk(k=k, dim=-1)[1]   # (batch_size, num_points, k)
    return idx


def get_graph_feature(x, k=20, idx=None, dim9=False):
    batch_size = x.size(0)
    num_points = x.size(2)
    x = x.view(batch_size, -1, num_points)
    if idx is None:
        if dim9 == False:
            idx = knn(x, k=k)   # (batch_size, num_points, k)
        else:
            idx = knn(x[:, 6:], k=k)
    device = torch.device('cuda')

    idx_base = torch.arange(0, batch_size, device=device).view(-1, 1, 1)*num_points

    idx = idx + idx_base

    idx = idx.view(-1)
 
    _, num_dims, _ = x.size()

    x = x.transpose(2, 1).contiguous()   # (batch_size, num_points, num_dims)  -> (batch_size*num_points, num_dims) #   batch_size * num_points * k + range(0, batch_size*num_points)
    feature = x.view(batch_size*num_points, -1)[idx, :]
    feature = feature.view(batch_size, num_points, k, num_dims) 
    x = x.view(batch_size, num_points, 1, num_dims).repeat(1, 1, k, 1)
    
    feature = torch.cat((feature-x, x), dim=3).permute(0, 3, 1, 2).contiguous()
  
    return feature      # (batch_size, 2*num_dims, num_points, k)


class PointNet(nn.Module):
    def __init__(self, args, output_channels=40):
        super(PointNet, self).__init__()
        self.args = args
        self.conv1 = nn.Conv1d(3, 64, kernel_size=1, bias=False)
        self.conv2 = nn.Conv1d(64, 64, kernel_size=1, bias=False)
        self.conv3 = nn.Conv1d(64, 64, kernel_size=1, bias=False)
        self.conv4 = nn.Conv1d(64, 128, kernel_size=1, bias=False)
        self.conv5 = nn.Conv1d(128, args.emb_dims, kernel_size=1, bias=False)
        self.bn1 = nn.BatchNorm1d(64)
        self.bn2 = nn.BatchNorm1d(64)
        self.bn3 = nn.BatchNorm1d(64)
        self.bn4 = nn.BatchNorm1d(128)
        self.bn5 = nn.BatchNorm1d(args.emb_dims)
        self.linear1 = nn.Linear(args.emb_dims, 512, bias=False)
        self.bn6 = nn.BatchNorm1d(512)
        self.dp1 = nn.Dropout()
        self.linear2 = nn.Linear(512, output_channels)

    def forward(self, x):
        x = F.relu(self.bn1(self.conv1(x)))
        x = F.relu(self.bn2(self.conv2(x)))
        x = F.relu(self.bn3(self.conv3(x)))
        x = F.relu(self.bn4(self.conv4(x)))
        x = F.relu(self.bn5(self.conv5(x)))
        x = F.adaptive_max_pool1d(x, 1).squeeze()
        x = F.relu(self.bn6(self.linear1(x)))
        x = self.dp1(x)
        x = self.linear2(x)
        return x


class DGCNN_cls(nn.Module):
    def __init__(self, args, output_channels=40):
        super(DGCNN_cls, self).__init__()
        self.args = args
        self.k = args.k
        
        self.bn1 = nn.BatchNorm2d(64)
        self.bn2 = nn.BatchNorm2d(64)
        self.bn3 = nn.BatchNorm2d(128)
        self.bn4 = nn.BatchNorm2d(256)
        self.bn5 = nn.BatchNorm1d(args.emb_dims)

        self.conv1 = nn.Sequential(nn.Conv2d(6, 64, kernel_size=1, bias=False),
                                   self.bn1,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.conv2 = nn.Sequential(nn.Conv2d(64*2, 64, kernel_size=1, bias=False),
                                   self.bn2,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.conv3 = nn.Sequential(nn.Conv2d(64*2, 128, kernel_size=1, bias=False),
                                   self.bn3,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.conv4 = nn.Sequential(nn.Conv2d(128*2, 256, kernel_size=1, bias=False),
                                   self.bn4,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.conv5 = nn.Sequential(nn.Conv1d(512, args.emb_dims, kernel_size=1, bias=False),
                                   self.bn5,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.linear1 = nn.Linear(args.emb_dims*2, 512, bias=False)
        self.bn6 = nn.BatchNorm1d(512)
        self.dp1 = nn.Dropout(p=args.dropout)
        self.linear2 = nn.Linear(512, 256)
        self.bn7 = nn.BatchNorm1d(256)
        self.dp2 = nn.Dropout(p=args.dropout)
        self.linear3 = nn.Linear(256, output_channels)

    def forward(self, x):
        batch_size = x.size(0)
        x = get_graph_feature(x, k=self.k)      # (batch_size, 3, num_points) -> (batch_size, 3*2, num_points, k)
        x = self.conv1(x)                       # (batch_size, 3*2, num_points, k) -> (batch_size, 64, num_points, k)
        x1 = x.max(dim=-1, keepdim=False)[0]    # (batch_size, 64, num_points, k) -> (batch_size, 64, num_points)

        x = get_graph_feature(x1, k=self.k)     # (batch_size, 64, num_points) -> (batch_size, 64*2, num_points, k)
        x = self.conv2(x)                       # (batch_size, 64*2, num_points, k) -> (batch_size, 64, num_points, k)
        x2 = x.max(dim=-1, keepdim=False)[0]    # (batch_size, 64, num_points, k) -> (batch_size, 64, num_points)

        x = get_graph_feature(x2, k=self.k)     # (batch_size, 64, num_points) -> (batch_size, 64*2, num_points, k)
        x = self.conv3(x)                       # (batch_size, 64*2, num_points, k) -> (batch_size, 128, num_points, k)
        x3 = x.max(dim=-1, keepdim=False)[0]    # (batch_size, 128, num_points, k) -> (batch_size, 128, num_points)

        x = get_graph_feature(x3, k=self.k)     # (batch_size, 128, num_points) -> (batch_size, 128*2, num_points, k)
        x = self.conv4(x)                       # (batch_size, 128*2, num_points, k) -> (batch_size, 256, num_points, k)
        x4 = x.max(dim=-1, keepdim=False)[0]    # (batch_size, 256, num_points, k) -> (batch_size, 256, num_points)

        x = torch.cat((x1, x2, x3, x4), dim=1)  # (batch_size, 64+64+128+256, num_points)

        x = self.conv5(x)                       # (batch_size, 64+64+128+256, num_points) -> (batch_size, emb_dims, num_points)
        x1 = F.adaptive_max_pool1d(x, 1).view(batch_size, -1)           # (batch_size, emb_dims, num_points) -> (batch_size, emb_dims)
        x2 = F.adaptive_avg_pool1d(x, 1).view(batch_size, -1)           # (batch_size, emb_dims, num_points) -> (batch_size, emb_dims)
        x = torch.cat((x1, x2), 1)              # (batch_size, emb_dims*2)

        x = F.leaky_relu(self.bn6(self.linear1(x)), negative_slope=0.2) # (batch_size, emb_dims*2) -> (batch_size, 512)
        x = self.dp1(x)
        x = F.leaky_relu(self.bn7(self.linear2(x)), negative_slope=0.2) # (batch_size, 512) -> (batch_size, 256)
        x = self.dp2(x)
        x = self.linear3(x)                                             # (batch_size, 256) -> (batch_size, output_channels)
        
        return x


class Transform_Net(nn.Module):
    def __init__(self, args):
        super(Transform_Net, self).__init__()
        self.args = args
        self.k = 3

        self.bn1 = nn.BatchNorm2d(64)
        self.bn2 = nn.BatchNorm2d(128)
        self.bn3 = nn.BatchNorm1d(1024)

        self.conv1 = nn.Sequential(nn.Conv2d(6, 64, kernel_size=1, bias=False),
                                   self.bn1,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.conv2 = nn.Sequential(nn.Conv2d(64, 128, kernel_size=1, bias=False),
                                   self.bn2,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.conv3 = nn.Sequential(nn.Conv1d(128, 1024, kernel_size=1, bias=False),
                                   self.bn3,
                                   nn.LeakyReLU(negative_slope=0.2))

        self.linear1 = nn.Linear(1024, 512, bias=False)
        self.bn3 = nn.BatchNorm1d(512)
        self.linear2 = nn.Linear(512, 256, bias=False)
        self.bn4 = nn.BatchNorm1d(256)

        self.transform = nn.Linear(256, 3*3)
        init.constant_(self.transform.weight, 0)
        init.eye_(self.transform.bias.view(3, 3))

    def forward(self, x):
        batch_size = x.size(0)

        x = self.conv1(x)                       # (batch_size, 3*2, num_points, k) -> (batch_size, 64, num_points, k)
        x = self.conv2(x)                       # (batch_size, 64, num_points, k) -> (batch_size, 128, num_points, k)
        x = x.max(dim=-1, keepdim=False)[0]     # (batch_size, 128, num_points, k) -> (batch_size, 128, num_points)

        x = self.conv3(x)                       # (batch_size, 128, num_points) -> (batch_size, 1024, num_points)
        x = x.max(dim=-1, keepdim=False)[0]     # (batch_size, 1024, num_points) -> (batch_size, 1024)

        x = F.leaky_relu(self.bn3(self.linear1(x)), negative_slope=0.2)     # (batch_size, 1024) -> (batch_size, 512)
        x = F.leaky_relu(self.bn4(self.linear2(x)), negative_slope=0.2)     # (batch_size, 512) -> (batch_size, 256)

        x = self.transform(x)                   # (batch_size, 256) -> (batch_size, 3*3)
        x = x.view(batch_size, 3, 3)            # (batch_size, 3*3) -> (batch_size, 3, 3)

        return x


class DGCNN_partseg(nn.Module):
    def __init__(self, args, seg_num_all):
        super(DGCNN_partseg, self).__init__()
        self.args = args
        self.seg_num_all = seg_num_all
        self.k = args.k
        self.transform_net = Transform_Net(args)
        
        self.bn1 = nn.BatchNorm2d(64)
        self.bn2 = nn.BatchNorm2d(64)
        self.bn3 = nn.BatchNorm2d(64)
        self.bn4 = nn.BatchNorm2d(64)
        self.bn5 = nn.BatchNorm2d(64)
        self.bn6 = nn.BatchNorm1d(args.emb_dims)
        self.bn7 = nn.BatchNorm1d(64)
        self.bn8 = nn.BatchNorm1d(256)
        self.bn9 = nn.BatchNorm1d(256)
        self.bn10 = nn.BatchNorm1d(128)

        self.conv1 = nn.Sequential(nn.Conv2d(6, 64, kernel_size=1, bias=False),
                                   self.bn1,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.conv2 = nn.Sequential(nn.Conv2d(64, 64, kernel_size=1, bias=False),
                                   self.bn2,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.conv3 = nn.Sequential(nn.Conv2d(64*2, 64, kernel_size=1, bias=False),
                                   self.bn3,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.conv4 = nn.Sequential(nn.Conv2d(64, 64, kernel_size=1, bias=False),
                                   self.bn4,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.conv5 = nn.Sequential(nn.Conv2d(64*2, 64, kernel_size=1, bias=False),
                                   self.bn5,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.conv6 = nn.Sequential(nn.Conv1d(192, args.emb_dims, kernel_size=1, bias=False),
                                   self.bn6,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.conv7 = nn.Sequential(nn.Conv1d(16, 64, kernel_size=1, bias=False),
                                   self.bn7,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.conv8 = nn.Sequential(nn.Conv1d(1280, 256, kernel_size=1, bias=False),
                                   self.bn8,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.dp1 = nn.Dropout(p=args.dropout)
        self.conv9 = nn.Sequential(nn.Conv1d(256, 256, kernel_size=1, bias=False),
                                   self.bn9,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.dp2 = nn.Dropout(p=args.dropout)
        self.conv10 = nn.Sequential(nn.Conv1d(256, 128, kernel_size=1, bias=False),
                                   self.bn10,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.conv11 = nn.Conv1d(128, self.seg_num_all, kernel_size=1, bias=False)
        

    def forward(self, x, l):
        batch_size = x.size(0)
        num_points = x.size(2)

        x0 = get_graph_feature(x, k=self.k)     # (batch_size, 3, num_points) -> (batch_size, 3*2, num_points, k)
        t = self.transform_net(x0)              # (batch_size, 3, 3)
        x = x.transpose(2, 1)                   # (batch_size, 3, num_points) -> (batch_size, num_points, 3)
        x = torch.bmm(x, t)                     # (batch_size, num_points, 3) * (batch_size, 3, 3) -> (batch_size, num_points, 3)
        x = x.transpose(2, 1)                   # (batch_size, num_points, 3) -> (batch_size, 3, num_points)

        x = get_graph_feature(x, k=self.k)      # (batch_size, 3, num_points) -> (batch_size, 3*2, num_points, k)
        x = self.conv1(x)                       # (batch_size, 3*2, num_points, k) -> (batch_size, 64, num_points, k)
        x = self.conv2(x)                       # (batch_size, 64, num_points, k) -> (batch_size, 64, num_points, k)
        x1 = x.max(dim=-1, keepdim=False)[0]    # (batch_size, 64, num_points, k) -> (batch_size, 64, num_points)

        x = get_graph_feature(x1, k=self.k)     # (batch_size, 64, num_points) -> (batch_size, 64*2, num_points, k)
        x = self.conv3(x)                       # (batch_size, 64*2, num_points, k) -> (batch_size, 64, num_points, k)
        x = self.conv4(x)                       # (batch_size, 64, num_points, k) -> (batch_size, 64, num_points, k)
        x2 = x.max(dim=-1, keepdim=False)[0]    # (batch_size, 64, num_points, k) -> (batch_size, 64, num_points)

        x = get_graph_feature(x2, k=self.k)     # (batch_size, 64, num_points) -> (batch_size, 64*2, num_points, k)
        x = self.conv5(x)                       # (batch_size, 64*2, num_points, k) -> (batch_size, 64, num_points, k)
        x3 = x.max(dim=-1, keepdim=False)[0]    # (batch_size, 64, num_points, k) -> (batch_size, 64, num_points)

        x = torch.cat((x1, x2, x3), dim=1)      # (batch_size, 64*3, num_points)

        x = self.conv6(x)                       # (batch_size, 64*3, num_points) -> (batch_size, emb_dims, num_points)
        x = x.max(dim=-1, keepdim=True)[0]      # (batch_size, emb_dims, num_points) -> (batch_size, emb_dims, 1)

        l = l.view(batch_size, -1, 1)           # (batch_size, num_categoties, 1)
        l = self.conv7(l)                       # (batch_size, num_categoties, 1) -> (batch_size, 64, 1)

        x = torch.cat((x, l), dim=1)            # (batch_size, 1088, 1)
        x = x.repeat(1, 1, num_points)          # (batch_size, 1088, num_points)

        x = torch.cat((x, x1, x2, x3), dim=1)   # (batch_size, 1088+64*3, num_points)

        x = self.conv8(x)                       # (batch_size, 1088+64*3, num_points) -> (batch_size, 256, num_points)
        x = self.dp1(x)
        x = self.conv9(x)                       # (batch_size, 256, num_points) -> (batch_size, 256, num_points)
        x = self.dp2(x)
        x = self.conv10(x)                      # (batch_size, 256, num_points) -> (batch_size, 128, num_points)
        x = self.conv11(x)                      # (batch_size, 256, num_points) -> (batch_size, seg_num_all, num_points)
        
        return x


class DGCNN_semseg_s3dis(nn.Module):
    def __init__(self, args):
        super(DGCNN_semseg_s3dis, self).__init__()
        self.args = args
        self.k = args.k
        
        self.bn1 = nn.BatchNorm2d(64)
        self.bn2 = nn.BatchNorm2d(64)
        self.bn3 = nn.BatchNorm2d(64)
        self.bn4 = nn.BatchNorm2d(64)
        self.bn5 = nn.BatchNorm2d(64)
        self.bn6 = nn.BatchNorm1d(args.emb_dims)
        self.bn7 = nn.BatchNorm1d(512)
        self.bn8 = nn.BatchNorm1d(256)

        self.conv1 = nn.Sequential(nn.Conv2d(18, 64, kernel_size=1, bias=False),
                                   self.bn1,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.conv2 = nn.Sequential(nn.Conv2d(64, 64, kernel_size=1, bias=False),
                                   self.bn2,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.conv3 = nn.Sequential(nn.Conv2d(64*2, 64, kernel_size=1, bias=False),
                                   self.bn3,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.conv4 = nn.Sequential(nn.Conv2d(64, 64, kernel_size=1, bias=False),
                                   self.bn4,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.conv5 = nn.Sequential(nn.Conv2d(64*2, 64, kernel_size=1, bias=False),
                                   self.bn5,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.conv6 = nn.Sequential(nn.Conv1d(192, args.emb_dims, kernel_size=1, bias=False),
                                   self.bn6,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.conv7 = nn.Sequential(nn.Conv1d(1216, 512, kernel_size=1, bias=False),
                                   self.bn7,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.conv8 = nn.Sequential(nn.Conv1d(512, 256, kernel_size=1, bias=False),
                                   self.bn8,
                                   nn.LeakyReLU(negative_slope=0.2))
        self.dp1 = nn.Dropout(p=args.dropout)
        self.conv9 = nn.Conv1d(256, 13, kernel_size=1, bias=False)
        

    def forward(self, x):
        batch_size = x.size(0)
        num_points = x.size(2)

        x = get_graph_feature(x, k=self.k, dim9=True)   # (batch_size, 9, num_points) -> (batch_size, 9*2, num_points, k)
        x = self.conv1(x)                       # (batch_size, 9*2, num_points, k) -> (batch_size, 64, num_points, k)
        x = self.conv2(x)                       # (batch_size, 64, num_points, k) -> (batch_size, 64, num_points, k)
        x1 = x.max(dim=-1, keepdim=False)[0]    # (batch_size, 64, num_points, k) -> (batch_size, 64, num_points)

        x = get_graph_feature(x1, k=self.k)     # (batch_size, 64, num_points) -> (batch_size, 64*2, num_points, k)
        x = self.conv3(x)                       # (batch_size, 64*2, num_points, k) -> (batch_size, 64, num_points, k)
        x = self.conv4(x)                       # (batch_size, 64, num_points, k) -> (batch_size, 64, num_points, k)
        x2 = x.max(dim=-1, keepdim=False)[0]    # (batch_size, 64, num_points, k) -> (batch_size, 64, num_points)

        x = get_graph_feature(x2, k=self.k)     # (batch_size, 64, num_points) -> (batch_size, 64*2, num_points, k)
        x = self.conv5(x)                       # (batch_size, 64*2, num_points, k) -> (batch_size, 64, num_points, k)
        x3 = x.max(dim=-1, keepdim=False)[0]    # (batch_size, 64, num_points, k) -> (batch_size, 64, num_points)

        x = torch.cat((x1, x2, x3), dim=1)      # (batch_size, 64*3, num_points)

        x = self.conv6(x)                       # (batch_size, 64*3, num_points) -> (batch_size, emb_dims, num_points)
        x = x.max(dim=-1, keepdim=True)[0]      # (batch_size, emb_dims, num_points) -> (batch_size, emb_dims, 1)

        x = x.repeat(1, 1, num_points)          # (batch_size, 1024, num_points)
        x = torch.cat((x, x1, x2, x3), dim=1)   # (batch_size, 1024+64*3, num_points)

        x = self.conv7(x)                       # (batch_size, 1024+64*3, num_points) -> (batch_size, 512, num_points)
        x = self.conv8(x)                       # (batch_size, 512, num_points) -> (batch_size, 256, num_points)
        x = self.dp1(x)
        x = self.conv9(x)                       # (batch_size, 256, num_points) -> (batch_size, 13, num_points)
        
        return x
        

class DGCNN_semseg_scannet(nn.Module):
    def __init__(self, num_classes, k=20, emb_dims=1024, dropout=0.5):
        super(DGCNN_semseg_scannet, self).__init__()

        self.k = k

        self.bn1 = nn.BatchNorm2d(64)
        self.bn2 = nn.BatchNorm2d(64)
        self.bn3 = nn.BatchNorm2d(64)
        self.bn4 = nn.BatchNorm2d(64)
        self.bn5 = nn.BatchNorm2d(64)
        self.bn6 = nn.BatchNorm1d(emb_dims)
        self.bn7 = nn.BatchNorm1d(512)
        self.bn8 = nn.BatchNorm1d(256)

        self.conv1 = nn.Sequential(
            nn.Conv2d(18, 64, kernel_size=1, bias=False),
            self.bn1,
            nn.LeakyReLU(negative_slope=0.2))
        self.conv2 = nn.Sequential(
            nn.Conv2d(64, 64, kernel_size=1, bias=False),
            self.bn2,
            nn.LeakyReLU(negative_slope=0.2))
        self.conv3 = nn.Sequential(
            nn.Conv2d(64*2, 64, kernel_size=1, bias=False),
            self.bn3,
            nn.LeakyReLU(negative_slope=0.2))
        self.conv4 = nn.Sequential(
            nn.Conv2d(64, 64, kernel_size=1, bias=False),
            self.bn4,
            nn.LeakyReLU(negative_slope=0.2))
        self.conv5 = nn.Sequential(
            nn.Conv2d(64*2, 64, kernel_size=1, bias=False),
            self.bn5,
            nn.LeakyReLU(negative_slope=0.2))
        self.conv6 = nn.Sequential(
            nn.Conv1d(192, emb_dims, kernel_size=1, bias=False),
            self.bn6,
            nn.LeakyReLU(negative_slope=0.2))
        self.conv7 = nn.Sequential(
            nn.Conv1d(1216, 512, kernel_size=1, bias=False),
            self.bn7,
            nn.LeakyReLU(negative_slope=0.2))
        self.conv8 = nn.Sequential(
            nn.Conv1d(512, 256, kernel_size=1, bias=False),
            self.bn8,
            nn.LeakyReLU(negative_slope=0.2))
        self.dp1 = nn.Dropout(p=dropout)
        self.conv9 = nn.Conv1d(256, num_classes, kernel_size=1, bias=False)

    def forward(self, x):
        bs = x.size(0)
        npoint = x.size(2)

        # (bs, 9, npoint) -> (bs, 9*2, npoint, k)
        x = get_graph_feature(x, k=self.k, dim9=True)
        # (bs, 9*2, npoint, k) -> (bs, 64, npoint, k)
        x = self.conv1(x)
        # (bs, 64, npoint, k) -> (bs, 64, npoint, k)
        x = self.conv2(x)
        # (bs, 64, npoint, k) -> (bs, 64, npoint)
        x1 = x.max(dim=-1, keepdim=False)[0]

        # (bs, 64, npoint) -> (bs, 64*2, npoint, k)
        x = get_graph_feature(x1, k=self.k)
        # (bs, 64*2, npoint, k) -> (bs, 64, npoint, k)
        x = self.conv3(x)
        # (bs, 64, npoint, k) -> (bs, 64, npoint, k)
        x = self.conv4(x)
        # (bs, 64, npoint, k) -> (bs, 64, npoint)
        x2 = x.max(dim=-1, keepdim=False)[0]

        # (bs, 64, npoint) -> (bs, 64*2, npoint, k)
        x = get_graph_feature(x2, k=self.k)
        # (bs, 64*2, npoint, k) -> (bs, 64, npoint, k)
        x = self.conv5(x)
        # (bs, 64, npoint, k) -> (bs, 64, npoint)
        x3 = x.max(dim=-1, keepdim=False)[0]

        x = torch.cat((x1, x2, x3), dim=1)      # (bs, 64*3, npoint)

        # (bs, 64*3, npoint) -> (bs, emb_dims, npoint)
        x = self.conv6(x)
        # (bs, emb_dims, npoint) -> (bs, emb_dims, 1)
        x = x.max(dim=-1, keepdim=True)[0]

        x = x.repeat(1, 1, npoint)          # (bs, 1024, npoint)
        x = torch.cat((x, x1, x2, x3), dim=1)   # (bs, 1024+64*3, npoint)

        # (bs, 1024+64*3, npoint) -> (bs, 512, npoint)
        x = self.conv7(x)
        # (bs, 512, npoint) -> (bs, 256, npoint)
        x = self.conv8(x)
        x = self.dp1(x)
        # (bs, 256, npoint) -> (bs, 13, npoint)
        x = self.conv9(x)
        # (bs, 13, npoint) -> (bs, npoint, 13)
        x = x.transpose(2, 1).contiguous()

        return x, None