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cosmetic change
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Signed-off-by: Yukihiro Saito <yukky.saito@gmail.com>
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yukkysaito committed Apr 4, 2022
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Expand Up @@ -26,12 +26,15 @@ The ray trace is done by Bresenham's line algorithm.
![Bresenham's line algorithm](./image/bresenham.svg)

1. Initialize freespace to the farthest point of each bin.

![pointcloud_based_occupancy_grid_map_side_view_1st](./image/pointcloud_based_occupancy_grid_map_side_view_1st.svg)

2. Fill in the unknown cells.
Assume that unknown is behind the obstacle, since the back of the obstacle is a blind spot.
Therefore, the unknown are assumed to be the cells that are more than a distance margin from each obstacle point.

![pointcloud_based_occupancy_grid_map_side_view_2nd](./image/pointcloud_based_occupancy_grid_map_side_view_2nd.svg)

There are three reasons for setting a distance margin.

- It is unlikely that a point on the ground will be immediately behind an obstacle.
Expand All @@ -41,6 +44,7 @@ The ray trace is done by Bresenham's line algorithm.
3. Fill in the occupied cells.
Fill in the point where the obstacle point is located with occupied.
In addition, If the distance between obstacle points is less than or equal to the distance margin, it is filled with occupied because the input may be inaccurate and obstacle points may not be determined as obstacles.

![pointcloud_based_occupancy_grid_map_side_view_3rd](./image/pointcloud_based_occupancy_grid_map_side_view_3rd.svg)

### 3rd step
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