Add multi_scale_3d_strides in 3D ResBackbone (#761)

* add dynamic pillar vfe

* make the upperbound unaccessible

* add place holder for voxel generation

* add DynPillarVFE

* add PFNLayerV2

* add try except for torch_scatter package

* add dynamic pillar in readme

* add the cfg file of centerpoint with dynamic pillar

* recover original mask_points_by_range

* masking points with points_coords out of grid_size

* add dynamic voxelization and config for voxel_rcnn

* add multi_scale_3d_strides in resbackbone

pcdet/models/backbones_3d/spconv_backbone.py

@@ -281,4 +281,13 @@ class VoxelResBackBone8x(nn.Module):
             }
         })
 
+        batch_dict.update({
+            'multi_scale_3d_strides': {
+                'x_conv1': 1,
+                'x_conv2': 2,
+                'x_conv3': 4,
+                'x_conv4': 8,
+            }
+        })
+        
         return batch_dict