本文介绍基于Paddle2.0实现Kd-Networks对点云分类处理。Kd-Networks引入Kd-Tree结构，将非结构化点云转为结构化数据，用1*1卷积近似KD算子。使用ShapeNet的.h5数据集，经数据处理、网络定义等步骤，训练20轮后，训练集准确率0.978，测试集0.9375，展示了其处理点云分类的效果。

点云处理：基于Paddle2.0实现Kd-Networks对点云进行分类处理

网络简介

    Kd-Networks于2017发表于ICCV上。创新性地引入了Kd-Tree结构用于处理点云。

    论文：Escape from Cells: Deep Kd-Networks for the Recognition of 3D Point Cloud Models

       

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项目效果

训练二十轮后的准确率：

       

项目说明

①数据集

    本次用到的数据集是ShapeNet，储存格式是.h5文件。

    .h5储存的key值分别为：

    1、data：这一份数据中所有点的xyz坐标，

    2、label：这一份数据所属类别，如airplane等，

    3、pid：这一份数据中所有点所属的类型，如这一份数据属airplane类，则它包含的所有点的类型有机翼、机身等类型。

       

②Kd-Networks 简介

    一、Kd-Networks最大的创新点在于引入了Kd-Tree这一结构，Kd-Tree将非结构化点云变成结构化数据，构建了处理非结构化点云的特征工程。

    二、该项目利用1*1卷积近似实现KD算子的功能，因此在构建Kd-Networks网络时，构建的是一个类Kd-Tree的网络，也就是说Kd-Networks将数据处理中Kd-Tree化的过程复刻到网络上（例如在index_select处可以看到，index_select复刻的是数据处理时Kd-Tree化中二叉时切割的维度），网络因此类Kd-Tree。

            

项目主体

①解压数据集、导入需要的库

In [ ]

!unzip data/data67117/shapenet_part_seg_hdf5_data.zip!mv hdf5_data dataset

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import osimport numpy as npimport randomimport h5pyimport paddleimport paddle.nn as nnimport paddle.nn.functional as Ffrom tools.build_KDTree import build_KDTree

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②数据处理

1、生成训练和测试样本的list

In [2]

train_list = ['ply_data_train0.h5', 'ply_data_train1.h5', 'ply_data_train2.h5', 'ply_data_train3.h5', 'ply_data_train4.h5', 'ply_data_train5.h5']test_list = ['ply_data_test0.h5', 'ply_data_test1.h5']val_list = ['ply_data_val0.h5']

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2、数据读取

    注：在数据读取这里，可以借助scipy.spatial中的cKDTree很快地生成kdTree。

       

In [3]

def pointDataLoader(mode='train'):    path = './dataset/'    BATCHSIZE = 64    MAX_POINT = 1024    LEVELS = (np.log(MAX_POINT) / np.log(2)).astype(int)    datas = []    split_dims_v = []    points_v = []    labels = []    if mode == 'train':        for file_list in train_list:            f = h5py.File(os.path.join(path, file_list), 'r')            datas.extend(f['data'][:, :MAX_POINT, :])            labels.extend(f['label'])            f.close()    elif mode == 'test':        for file_list in test_list:            f = h5py.File(os.path.join(path, file_list), 'r')            datas.extend(f['data'][:, :MAX_POINT, :])            labels.extend(f['label'])            f.close()    else:        for file_list in val_list:            f = h5py.File(os.path.join(path, file_list), 'r')            datas.extend(f['data'][:, :MAX_POINT, :])            labels.extend(f['label'])            f.close()    datas = np.array(datas)    for i in range(len(datas)):        split_dim, tree = build_KDTree(datas[i], depth=LEVELS)        split_dim_v = [np.array(item).astype(np.int64) for item in split_dim]        split_dims_v.append(split_dim_v)        points_v.append(tree[-1].transpose(0, 2, 1))    split_dims_v = np.array(split_dims_v)    points_v = np.array(points_v)    labels = np.array(labels)    print('==========load over==========')    index_list = list(range(len(datas)))    def pointDataGenerator():        if mode == 'train':            random.shuffle(index_list)        split_dims_v_list = []        points_v_list = []        labels_list = []        for i in index_list:            split_dims_v_list.append(split_dims_v[i])            points_v_list.append(points_v[i].astype('float32'))             labels_list.append(labels[i].astype('int64'))            if len(labels_list) == BATCHSIZE:                yield np.array(split_dims_v_list), np.array(points_v_list), np.array(labels_list)                split_dims_v_list = []                points_v_list = []                labels_list = []        if len(labels_list) > 0:            yield np.array(split_dims_v_list), np.array(points_v_list), np.array(labels_list)    return pointDataGenerator

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③定义网络

In [10]

class KDNet(nn.Layer):    def __init__(self, k=16):        super(KDNet, self).__init__()        self.conv1 = nn.Conv1D(3, 32*3, 1, 1)        self.conv2 = nn.Conv1D(32, 64*3, 1, 1)        self.conv3 = nn.Conv1D(64, 64*3, 1, 1)        self.conv4 = nn.Conv1D(64, 128*3, 1, 1)        self.conv5 = nn.Conv1D(128, 128*3, 1, 1)        self.conv6 = nn.Conv1D(128, 256*3, 1, 1)        self.conv7 = nn.Conv1D(256, 256*3, 1, 1)        self.conv8 = nn.Conv1D(256, 512*3, 1, 1)        self.conv9 = nn.Conv1D(512, 512*3, 1, 1)        self.conv10 = nn.Conv1D(512, 128*3, 1, 1)        self.fc = nn.Linear(128, k)    def forward(self, x, split_dims_v):        def kdconv(x, dim, featdim, select, conv):            x = F.relu(conv(x))            x = paddle.reshape(x, (-1, featdim, 3, dim))            x = paddle.reshape(x, (-1, featdim, 3 * dim))            select = paddle.to_tensor(select) + (paddle.arange(0, dim) * 3)            x = paddle.index_select(x, axis=2, index=select)                x = paddle.reshape(x, (-1, featdim, int(dim/2), 2))            x = paddle.max(x, axis=-1)            return x        x = kdconv(x, 1024, 32, split_dims_v[0], self.conv1)        x = kdconv(x, 512, 64, split_dims_v[1], self.conv2)        x = kdconv(x, 256, 64, split_dims_v[2], self.conv3)        x = kdconv(x, 128, 128, split_dims_v[3], self.conv4)        x = kdconv(x, 64, 128, split_dims_v[4], self.conv5)        x = kdconv(x, 32, 256, split_dims_v[5], self.conv6)        x = kdconv(x, 16, 256, split_dims_v[6], self.conv7)        x = kdconv(x, 8, 512, split_dims_v[7], self.conv8)        x = kdconv(x, 4, 512, split_dims_v[8], self.conv9)        x = kdconv(x, 2, 128, split_dims_v[9], self.conv10)        x = paddle.reshape(x, (-1, 128))        x = F.log_softmax(self.fc(x))        return x

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⑤训练

1、创建训练数据读取器

    注：由于训练数据预处理比较慢，所以先创建训练数据读取器（创建同时会对数据进行预处理），这样在训练时候直接导入就显得训练过程快很多（实际上并没有节省时间，只不过是为了调试方便和读者尝试，把训练数据读取器单独拿出来创建）。

       

In [5]

train_loader = pointDataLoader(mode='train')

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==========load over==========

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2、开始训练

In [11]

def train():    model = KDNet()    model.train()    optim = paddle.optimizer.Adam(parameters=model.parameters(), weight_decay=0.001)    epoch_num = 40    for epoch in range(epoch_num):        for batch_id, data in enumerate(train_loader()):            split_dims_v = data[0]            points_v = data[1]            labels = data[2]            inputs = paddle.to_tensor(points_v)            labels = paddle.to_tensor(labels)            predict = []            for i in range(split_dims_v.shape[0]):                predict.extend(model(inputs[i], split_dims_v[i]))            predicts = paddle.stack(predict)            loss = F.nll_loss(predicts, labels)            acc = paddle.metric.accuracy(predicts, labels)                    if batch_id % 10 == 0:                 print("epoch: {}, batch_id: {}, loss is: {}, accuracy is: {}".format(epoch, batch_id, loss.numpy(), acc.numpy()))                        loss.backward()            optim.step()            optim.clear_grad()        if epoch % 2 == 0:            paddle.save(model.state_dict(), './model/KDNet.pdparams')            paddle.save(optim.state_dict(), './model/KDNet.pdopt')if __name__ == '__main__':    train()

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⑥评估

In [12]

def evaluation():    test_loader = pointDataLoader(mode='test')    model = KDNet()    model_state_dict = paddle.load('./model/KDNet.pdparams')    model.load_dict(model_state_dict)    for batch_id, data in enumerate(test_loader()):        split_dims_v = data[0]        points_v = data[1]        labels = data[2]        inputs = paddle.to_tensor(points_v)        labels = paddle.to_tensor(labels)        predict = []        for i in range(split_dims_v.shape[0]):            predict.extend(model(inputs[i], split_dims_v[i]))        predicts = paddle.stack(predict)        acc = paddle.metric.accuracy(predicts, labels)        print("eval accuracy is: {}".format(acc.numpy()))        break;if __name__ == '__main__':    evaluation()

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==========load over==========eval accuracy is: [0.9375]

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