[ros-users] Clearing cells in Costmap2DROS

[Sabrina Kliegl]

Hi,

after some more experiments I can see the heart of the problem:

I am using the default voxel map. Thus, when a huge object (like a leg) is 
detected with the stereo camera several cells in the voxel map in the z-
direction are marked as obstacle cells. When the object has left the field of 
view the lines from the camera center to  "free" points are cleared. In 
general some voxel along the z-axis remain marked and result in a marked cell 
in the 2D costmap. 

Hopefully the following "drawings" help  to understand what I am trying to 
explain: 

1. Leg is in field of view   
   (z-axis)                                      
      | |    >o(camera)                                          
      | |                   
      | |                                        
      | |                                        
-----------> x     

2. Marked cells in the voxel grid  

 (z-axis)                                      
      X    >o(camera)                                      
      X                       
      X                                        
      X                                        
-----------> x     
      
 ___O____  resulting costmap (O: obstacle)

3. Leg has left field of view -> clearing of the voxel grid is done line-wise -
> not all cells in z-direction are cleared -> after the projection of the 
voxel grid on the costmap the cell is still marked as obstacle

 (z-axis)                                      
      X    >o(camera)                                       
      X  /            
      X/                                  
      /                                 
__ /_------> x 

 ___O____  (resulting costmap)  (O: obstacle)

After changing the map_type to "costmap", the costmap behaves as I want it to.

Regards,
Sabrina