From c9e28423245a818929f1ce23f20a1085ea8eb56f Mon Sep 17 00:00:00 2001
From: inter <inter@qq.com>
Date: Sun, 21 Sep 2025 20:18:57 +0800
Subject: [PATCH] Add File

---
 .../vfe/image_vfe_modules/ffn/depth_ffn.py    | 103 ++++++++++++++++++
 1 file changed, 103 insertions(+)
 create mode 100644 pcdet/models/backbones_3d/vfe/image_vfe_modules/ffn/depth_ffn.py

diff --git a/pcdet/models/backbones_3d/vfe/image_vfe_modules/ffn/depth_ffn.py b/pcdet/models/backbones_3d/vfe/image_vfe_modules/ffn/depth_ffn.py
new file mode 100644
index 0000000..c35e229
--- /dev/null
+++ b/pcdet/models/backbones_3d/vfe/image_vfe_modules/ffn/depth_ffn.py
@@ -0,0 +1,103 @@
+import torch.nn as nn
+import torch.nn.functional as F
+
+from . import ddn, ddn_loss
+from pcdet.models.model_utils.basic_block_2d import BasicBlock2D
+
+
+class DepthFFN(nn.Module):
+
+    def __init__(self, model_cfg, downsample_factor):
+        """
+        Initialize frustum feature network via depth distribution estimation
+        Args:
+            model_cfg: EasyDict, Depth classification network config
+            downsample_factor: int, Depth map downsample factor
+        """
+        super().__init__()
+        self.model_cfg = model_cfg
+        self.disc_cfg = model_cfg.DISCRETIZE
+        self.downsample_factor = downsample_factor
+
+        # Create modules
+        self.ddn = ddn.__all__[model_cfg.DDN.NAME](
+            num_classes=self.disc_cfg["num_bins"] + 1,
+            backbone_name=model_cfg.DDN.BACKBONE_NAME,
+            **model_cfg.DDN.ARGS
+        )
+        self.channel_reduce = BasicBlock2D(**model_cfg.CHANNEL_REDUCE)
+        self.ddn_loss = ddn_loss.__all__[model_cfg.LOSS.NAME](
+            disc_cfg=self.disc_cfg,
+            downsample_factor=downsample_factor,
+            **model_cfg.LOSS.ARGS
+        )
+        self.forward_ret_dict = {}
+
+    def get_output_feature_dim(self):
+        return self.channel_reduce.out_channels
+
+    def forward(self, batch_dict):
+        """
+        Predicts depths and creates image depth feature volume using depth distributions
+        Args:
+            batch_dict:
+                images: (N, 3, H_in, W_in), Input images
+        Returns:
+            batch_dict:
+                frustum_features: (N, C, D, H_out, W_out), Image depth features
+        """
+        # Pixel-wise depth classification
+        images = batch_dict["images"]
+        ddn_result = self.ddn(images)
+        image_features = ddn_result["features"]
+        depth_logits = ddn_result["logits"]
+
+        # Channel reduce
+        if self.channel_reduce is not None:
+            image_features = self.channel_reduce(image_features)
+
+        # Create image feature plane-sweep volume
+        frustum_features = self.create_frustum_features(image_features=image_features,
+                                                        depth_logits=depth_logits)
+        batch_dict["frustum_features"] = frustum_features
+
+        if self.training:
+            self.forward_ret_dict["depth_maps"] = batch_dict["depth_maps"]
+            self.forward_ret_dict["gt_boxes2d"] = batch_dict["gt_boxes2d"]
+            self.forward_ret_dict["depth_logits"] = depth_logits
+        return batch_dict
+
+    def create_frustum_features(self, image_features, depth_logits):
+        """
+        Create image depth feature volume by multiplying image features with depth distributions
+        Args:
+            image_features: (N, C, H, W), Image features
+            depth_logits: (N, D+1, H, W), Depth classification logits
+        Returns:
+            frustum_features: (N, C, D, H, W), Image features
+        """
+        channel_dim = 1
+        depth_dim = 2
+
+        # Resize to match dimensions
+        image_features = image_features.unsqueeze(depth_dim)
+        depth_logits = depth_logits.unsqueeze(channel_dim)
+
+        # Apply softmax along depth axis and remove last depth category (> Max Range)
+        depth_probs = F.softmax(depth_logits, dim=depth_dim)
+        depth_probs = depth_probs[:, :, :-1]
+
+        # Multiply to form image depth feature volume
+        frustum_features = depth_probs * image_features
+        return frustum_features
+
+    def get_loss(self):
+        """
+        Gets DDN loss
+        Args:
+        Returns:
+            loss: (1), Depth distribution network loss
+            tb_dict: dict[float], All losses to log in tensorboard
+        """
+        loss, tb_dict = self.ddn_loss(**self.forward_ret_dict)
+        return loss, tb_dict