How to change the origin of local costmap?

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Hello,

I am working on a project where I need an instantaneous occupancy grid. I managed to get the occupancy grid using costmap_2d package. Now the problem is that the occupancy grid generated has the robot exactly in the middle. But, I want the occupancy grid only in front of the robot. I tried changing origin_x and origin_y, but it doesn't have any effect.

max_obstacle_height: 0.60   
obstacle_range: 30 
raytrace_range: 30

footprint: [[0,-0.8], [0,0.8],[2.6,0.8],[2.6,-0.8],[0,-0.8]]  # if the robot is not circular 
inflation_radius: 0.50   
cost_scaling_factor: 5  

map_type: costmap transform_tolerance: 5 # seconds

# origin_x: -15.0
# origin_y: -30.0 
origin_z: 0.0 
z_resolution: 0.2 
z_voxels: 2
publish_voxel_map: false

global_frame: odom 
robot_base_frame: /base_footprint
# global_frame: azcar_sim/odom
# robot_base_frame: azcar_sim/base_link 
update_frequency: 5.0 
publish_frequency: 2.0 
static_map: false 
rolling_window: true 
width: 60 
height: 30 
resolution: 0.3 
transform_tolerance: 0.5 
plugins:
  - {name: obstacles, type: "costmap_2d::ObstacleLayer"} 
obstacles:   
   observation_sources: scan
# scan: {data_type: LaserScan, sensor_frame: azcar_sim/front_laser_link, topic: /azcar_sim/front_laser_points, marking:true, clearing: true, min_obstacle_height: 0.0, max_obstacle_height: 3}   scan: {data_type: LaserScan, sensor_frame: /base_laser_link, topic: /base_scan, marking: true, clearing: true, min_obstacle_height: 0.0, max_obstacle_height: 3}

Please refer to the images below.

The occupancy grid, I am getting using the above parameters.

The occupancy grid needed.