pointnet2_modules.py

import torch
import torch.nn as nn
import torch.nn.functional as F
from . import pointnet2_utils
from typing import List


class StackSAModuleMSG(nn.Module):

    def __init__(self, *, radii: List[float], nsamples: List[int], mlps: List[List[int]],
                 use_xyz: bool = True, pool_method='max_pool'):
        """
        Args:
            radii: list of float, list of radii to group with
            nsamples: list of int, number of samples in each ball query
            mlps: list of list of int, spec of the pointnet before the global pooling for each scale
            use_xyz:
            pool_method: max_pool / avg_pool
        """
        super().__init__()

        assert len(radii) == len(nsamples) == len(mlps)

        self.groupers = nn.ModuleList()
        self.mlps = nn.ModuleList()
        for i in range(len(radii)):
            radius = radii[i]
            nsample = nsamples[i]
            self.groupers.append(pointnet2_utils.QueryAndGroup(radius, nsample, use_xyz=use_xyz))
            mlp_spec = mlps[i]
            if use_xyz:
                mlp_spec[0] += 3

            shared_mlps = []
            for k in range(len(mlp_spec) - 1):
                shared_mlps.extend([
                    nn.Conv2d(mlp_spec[k], mlp_spec[k + 1], kernel_size=1, bias=False),
                    nn.BatchNorm2d(mlp_spec[k + 1]),
                    nn.ReLU()
                ])
            self.mlps.append(nn.Sequential(*shared_mlps))
        self.pool_method = pool_method

        self.init_weights()

    def init_weights(self):
        for m in self.modules():
            if isinstance(m, nn.Conv2d):
                nn.init.kaiming_normal_(m.weight)
                if m.bias is not None:
                    nn.init.constant_(m.bias, 0)
            if isinstance(m, nn.BatchNorm2d):
                nn.init.constant_(m.weight, 1.0)
                nn.init.constant_(m.bias, 0)

    def forward(self, xyz, xyz_batch_cnt, new_xyz, new_xyz_batch_cnt, features=None, empty_voxel_set_zeros=True):
        """
        :param xyz: (N1 + N2 ..., 3) tensor of the xyz coordinates of the features
        :param xyz_batch_cnt: (batch_size), [N1, N2, ...]
        :param new_xyz: (M1 + M2 ..., 3)
        :param new_xyz_batch_cnt: (batch_size), [M1, M2, ...]
        :param features: (N1 + N2 ..., C) tensor of the descriptors of the the features
        :return:
            new_xyz: (M1 + M2 ..., 3) tensor of the new features' xyz
            new_features: (M1 + M2 ..., \sum_k(mlps[k][-1])) tensor of the new_features descriptors
        """
        new_features_list = []
        for k in range(len(self.groupers)):
            new_features, ball_idxs = self.groupers[k](
                xyz, xyz_batch_cnt, new_xyz, new_xyz_batch_cnt, features
            )  # (M1 + M2, C, nsample)
            new_features = new_features.permute(1, 0, 2).unsqueeze(dim=0)  # (1, C, M1 + M2 ..., nsample)
            new_features = self.mlps[k](new_features)  # (1, C, M1 + M2 ..., nsample)

            if self.pool_method == 'max_pool':
                new_features = F.max_pool2d(
                    new_features, kernel_size=[1, new_features.size(3)]
                ).squeeze(dim=-1)  # (1, C, M1 + M2 ...)
            elif self.pool_method == 'avg_pool':
                new_features = F.avg_pool2d(
                    new_features, kernel_size=[1, new_features.size(3)]
                ).squeeze(dim=-1)  # (1, C, M1 + M2 ...)
            else:
                raise NotImplementedError
            new_features = new_features.squeeze(dim=0).permute(1, 0)  # (M1 + M2 ..., C)
            new_features_list.append(new_features)

        new_features = torch.cat(new_features_list, dim=1)  # (M1 + M2 ..., C)

        return new_xyz, new_features