From 12612b236a978246ca326449d476300c6e7b6342 Mon Sep 17 00:00:00 2001
From: inter <inter@qq.com>
Date: Sun, 21 Sep 2025 20:18:56 +0800
Subject: [PATCH] Add File

---
 .../ffn/ddn_loss/balancer.py                  | 50 +++++++++++++++++++
 1 file changed, 50 insertions(+)
 create mode 100644 pcdet/models/backbones_3d/vfe/image_vfe_modules/ffn/ddn_loss/balancer.py

diff --git a/pcdet/models/backbones_3d/vfe/image_vfe_modules/ffn/ddn_loss/balancer.py b/pcdet/models/backbones_3d/vfe/image_vfe_modules/ffn/ddn_loss/balancer.py
new file mode 100644
index 0000000..47bf8d4
--- /dev/null
+++ b/pcdet/models/backbones_3d/vfe/image_vfe_modules/ffn/ddn_loss/balancer.py
@@ -0,0 +1,50 @@
+import torch
+import torch.nn as nn
+
+from pcdet.utils import loss_utils
+
+
+class Balancer(nn.Module):
+    def __init__(self, fg_weight, bg_weight, downsample_factor=1):
+        """
+        Initialize fixed foreground/background loss balancer
+        Args:
+            fg_weight: float, Foreground loss weight
+            bg_weight: float, Background loss weight
+            downsample_factor: int, Depth map downsample factor
+        """
+        super().__init__()
+        self.fg_weight = fg_weight
+        self.bg_weight = bg_weight
+        self.downsample_factor = downsample_factor
+
+    def forward(self, loss, gt_boxes2d):
+        """
+        Forward pass
+        Args:
+            loss: (B, H, W), Pixel-wise loss
+            gt_boxes2d: (B, N, 4), 2D box labels for foreground/background balancing
+        Returns:
+            loss: (1), Total loss after foreground/background balancing
+            tb_dict: dict[float], All losses to log in tensorboard
+        """
+        # Compute masks
+        fg_mask = loss_utils.compute_fg_mask(gt_boxes2d=gt_boxes2d,
+                                             shape=loss.shape,
+                                             downsample_factor=self.downsample_factor,
+                                             device=loss.device)
+        bg_mask = ~fg_mask
+
+        # Compute balancing weights
+        weights = self.fg_weight * fg_mask + self.bg_weight * bg_mask
+        num_pixels = fg_mask.sum() + bg_mask.sum()
+
+        # Compute losses
+        loss *= weights
+        fg_loss = loss[fg_mask].sum() / num_pixels
+        bg_loss = loss[bg_mask].sum() / num_pixels
+
+        # Get total loss
+        loss = fg_loss + bg_loss
+        tb_dict = {"balancer_loss": loss.item(), "fg_loss": fg_loss.item(), "bg_loss": bg_loss.item()}
+        return loss, tb_dict