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# Copyright (C) 2024 Apple Inc. All Rights Reserved. | |
# Field of View network architecture. | |
from typing import Optional | |
import torch | |
from torch import nn | |
from torch.nn import functional as F | |
class FOVNetwork(nn.Module): | |
"""Field of View estimation network.""" | |
def __init__( | |
self, | |
num_features: int, | |
fov_encoder: Optional[nn.Module] = None, | |
): | |
"""Initialize the Field of View estimation block. | |
Args: | |
---- | |
num_features: Number of features used. | |
fov_encoder: Optional encoder to bring additional network capacity. | |
""" | |
super().__init__() | |
# Create FOV head. | |
fov_head0 = [ | |
nn.Conv2d( | |
num_features, num_features // 2, kernel_size=3, stride=2, padding=1 | |
), # 128 x 24 x 24 | |
nn.ReLU(True), | |
] | |
fov_head = [ | |
nn.Conv2d( | |
num_features // 2, num_features // 4, kernel_size=3, stride=2, padding=1 | |
), # 64 x 12 x 12 | |
nn.ReLU(True), | |
nn.Conv2d( | |
num_features // 4, num_features // 8, kernel_size=3, stride=2, padding=1 | |
), # 32 x 6 x 6 | |
nn.ReLU(True), | |
nn.Conv2d(num_features // 8, 1, kernel_size=6, stride=1, padding=0), | |
] | |
if fov_encoder is not None: | |
self.encoder = nn.Sequential( | |
fov_encoder, nn.Linear(fov_encoder.embed_dim, num_features // 2) | |
) | |
self.downsample = nn.Sequential(*fov_head0) | |
else: | |
fov_head = fov_head0 + fov_head | |
self.head = nn.Sequential(*fov_head) | |
def forward(self, x: torch.Tensor, lowres_feature: torch.Tensor) -> torch.Tensor: | |
"""Forward the fov network. | |
Args: | |
---- | |
x (torch.Tensor): Input image. | |
lowres_feature (torch.Tensor): Low resolution feature. | |
Returns: | |
------- | |
The field of view tensor. | |
""" | |
if hasattr(self, "encoder"): | |
x = F.interpolate( | |
x, | |
size=None, | |
scale_factor=0.25, | |
mode="bilinear", | |
align_corners=False, | |
) | |
x = self.encoder(x)[:, 1:].permute(0, 2, 1) | |
lowres_feature = self.downsample(lowres_feature) | |
x = x.reshape_as(lowres_feature) + lowres_feature | |
else: | |
x = lowres_feature | |
return self.head(x) | |