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examples/python/rrt_star/README.md

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This example visualizes the path finding algorithm RRT* in a simple environment.

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Used Rerun types

LineStrips2D, Points2D, TextDocument

Background

The algorithm finds a path between two points by randomly expanding a tree from the start point. After it has added a random edge to the tree it looks at nearby nodes to check if it's faster to reach them through this new edge instead, and if so it changes the parent of these nodes. This ensures that the algorithm will converge to the optimal path given enough time.

A detailed explanation can be found in the original paper Karaman, S. Frazzoli, S. 2011. "Sampling-based algorithms for optimal motion planning". or in this medium article

Logging and visualizing with Rerun

All points are logged using the Points2D archetype, while the lines are logged using the LineStrips2D LineStrips2D.

The visualizations in this example were created with the following Rerun code:

Map

Starting point

python
rr.log("map/start", rr.Points2D([start_point], radii=0.02, colors=[[255, 255, 255, 255]]))

Destination point

python
rr.log("map/destination", rr.Points2D([end_point], radii=0.02, colors=[[255, 255, 0, 255]]))

Obstacles

python
rr.log("map/obstacles", rr.LineStrips2D(self.obstacles))

RRT tree

Edges

python
rr.log("map/tree/edges", rr.LineStrips2D(tree.segments(), radii=0.0005, colors=[0, 0, 255, 128]))

New edges

python
rr.log("map/new/new_edge", rr.LineStrips2D([(closest_node.pos, new_point)], colors=[color], radii=0.001))

Vertices

python
rr.log(
    "map/tree/vertices",
    rr.Points2D([node.pos for node in tree], radii=0.002),
    rr.AnyValues(cost=[float(node.cost) for node in tree]),
)

Close nodes

python
rr.log("map/new/close_nodes", rr.Points2D([node.pos for node in close_nodes]))

Closest node

python
rr.log("map/new/closest_node", rr.Points2D([closest_node.pos], radii=0.008))

Random points

python
rr.log("map/new/random_point", rr.Points2D([random_point], radii=0.008))

New points

python
rr.log("map/new/new_point", rr.Points2D([new_point], radii=0.008))

Path

python
rr.log("map/path", rr.LineStrips2D(segments, radii=0.002, colors=[0, 255, 255, 255]))

Run the code

To run this example, make sure you have the Rerun repository checked out and the latest SDK installed:

bash
pip install --upgrade rerun-sdk  # install the latest Rerun SDK
git clone [email protected]:rerun-io/rerun.git  # Clone the repository
cd rerun
git checkout latest  # Check out the commit matching the latest SDK release

Install the necessary libraries specified in the requirements file:

bash
pip install -e examples/python/rrt_star

To experiment with the provided example, simply execute the main Python script:

bash
python -m rrt_star # run the example

If you wish to customize it, explore additional features, or save it use the CLI with the --help option for guidance:

bash
python -m rrt_star --help