[Refactor]: rename centerpoint coordinates of gt box length and width (#2385)

Author: yechenzhi

mmdet3d/models/dense_heads/centerpoint_head.py

@@ -519,16 +519,16 @@ def get_targets_single(self,
             for k in range(num_objs):
                 cls_id = task_classes[idx][k] - 1
 
-                width = task_boxes[idx][k][3]
-                length = task_boxes[idx][k][4]
-                width = width / voxel_size[0] / self.train_cfg[
+                length = task_boxes[idx][k][3]
+                width = task_boxes[idx][k][4]
+                length = length / voxel_size[0] / self.train_cfg[
                     'out_size_factor']
-                length = length / voxel_size[1] / self.train_cfg[
+                width = width / voxel_size[1] / self.train_cfg[
                     'out_size_factor']
 
                 if width > 0 and length > 0:
                     radius = gaussian_radius(
-                        (length, width),
+                        (width, length),
                         min_overlap=self.train_cfg['gaussian_overlap'])
                     radius = max(self.train_cfg['min_radius'], int(radius))