diff --git a/mmdet3d/core/bbox/structures/cam_box3d.py b/mmdet3d/core/bbox/structures/cam_box3d.py
index f87761afa3..0906371ef5 100644
--- a/mmdet3d/core/bbox/structures/cam_box3d.py
+++ b/mmdet3d/core/bbox/structures/cam_box3d.py
@@ -34,6 +34,41 @@ class CameraInstance3DBoxes(BaseInstance3DBoxes):
             boxes.
     """
 
+    def __init__(self,
+                 tensor,
+                 box_dim=7,
+                 with_yaw=True,
+                 origin=(0.5, 1.0, 0.5)):
+        if isinstance(tensor, torch.Tensor):
+            device = tensor.device
+        else:
+            device = torch.device('cpu')
+        tensor = torch.as_tensor(tensor, dtype=torch.float32, device=device)
+        if tensor.numel() == 0:
+            # Use reshape, so we don't end up creating a new tensor that
+            # does not depend on the inputs (and consequently confuses jit)
+            tensor = tensor.reshape((0, box_dim)).to(
+                dtype=torch.float32, device=device)
+        assert tensor.dim() == 2 and tensor.size(-1) == box_dim, tensor.size()
+
+        if tensor.shape[-1] == 6:
+            # If the dimension of boxes is 6, we expand box_dim by padding
+            # 0 as a fake yaw and set with_yaw to False.
+            assert box_dim == 6
+            fake_rot = tensor.new_zeros(tensor.shape[0], 1)
+            tensor = torch.cat((tensor, fake_rot), dim=-1)
+            self.box_dim = box_dim + 1
+            self.with_yaw = False
+        else:
+            self.box_dim = box_dim
+            self.with_yaw = with_yaw
+        self.tensor = tensor
+
+        if origin != (0.5, 1.0, 0.5):
+            dst = self.tensor.new_tensor((0.5, 1.0, 0.5))
+            src = self.tensor.new_tensor(origin)
+            self.tensor[:, :3] += self.tensor[:, 3:6] * (dst - src)
+
     @property
     def height(self):
         """torch.Tensor: A vector with height of each box."""