[Fix] NMS for Point RCNN (#1418)

* fix nms for point rcnn

* add else case

mmdet3d/models/dense_heads/point_rpn_head.py

@@ -3,6 +3,7 @@ import torch
 from mmcv.runner import BaseModule, force_fp32
 from torch import nn as nn
 
+from mmdet3d.core import xywhr2xyxyr
 from mmdet3d.core.bbox.structures import (DepthInstance3DBoxes,
                                           LiDARInstance3DBoxes)
 from mmdet3d.core.post_processing import nms_bev, nms_normal_bev
@@ -320,29 +321,33 @@ class PointRPNHead(BaseModule):
         else:
             raise NotImplementedError('Unsupported bbox type!')
 
-        bbox = bbox.tensor[nonempty_box_mask]
+        bbox = bbox[nonempty_box_mask]
 
         if self.test_cfg.score_thr is not None:
             score_thr = self.test_cfg.score_thr
             keep = (obj_scores >= score_thr)
             obj_scores = obj_scores[keep]
             sem_scores = sem_scores[keep]
-            bbox = bbox[keep]
+            bbox = bbox.tensor[keep]
 
         if obj_scores.shape[0] > 0:
             topk = min(nms_cfg.nms_pre, obj_scores.shape[0])
             obj_scores_nms, indices = torch.topk(obj_scores, k=topk)
-            bbox_for_nms = bbox[indices]
+            bbox_for_nms = xywhr2xyxyr(bbox[indices].bev)
             sem_scores_nms = sem_scores[indices]
 
-            keep = nms_func(bbox_for_nms[:, 0:7], obj_scores_nms,
-                            nms_cfg.iou_thr)
+            keep = nms_func(bbox_for_nms, obj_scores_nms, nms_cfg.iou_thr)
             keep = keep[:nms_cfg.nms_post]
 
-            bbox_selected = bbox_for_nms[keep]
+            bbox_selected = bbox.tensor[indices][keep]
             score_selected = obj_scores_nms[keep]
             cls_preds = sem_scores_nms[keep]
             labels = torch.argmax(cls_preds, -1)
+        else:
+            bbox_selected = bbox.tensor
+            score_selected = obj_scores.new_zeros([0])
+            labels = obj_scores.new_zeros([0])
+            cls_preds = obj_scores.new_zeros([0, sem_scores.shape[-1]])
 
         return bbox_selected, score_selected, labels, cls_preds