theta-star-planner

Add nav2_theta_star_planner::ThetaStarPlanner as a plugin under planner_server's GridBased planner in your YAML config. Set how_many_corners to 8 for diagonal movement, and tune w_euc_cost and w_traversal_cost to balance path length against obstacle avoidance.

Theta* extends A* with line-of-sight checks: when expanding a node, it tests whether the parent has direct visibility to each neighbor and skips intermediate cells if so. This produces straight any-angle paths instead of A*'s grid-constrained staircase paths.

Theta* produces any-angle straight-line paths with low turn counts, sitting between NavFn's simplicity and SMAC Hybrid-A*'s sophistication. Use Theta* for open indoor environments; use NavFn or SMAC 2D in very cluttered spaces where line-of-sight checks rarely succeed.

Grid-aligned paths usually mean how_many_corners is set to 4, limiting line-of-sight checks to cardinal directions. Set how_many_corners to 8 to enable diagonal movement and full any-angle planning.

Avoid Theta* for non-holonomic robots needing kinematically feasible paths from the planner (use Hybrid-A* instead), and in very cluttered environments where failed line-of-sight checks add overhead without benefit. It also cannot guarantee smoothness at obstacle corners.

Increase w_traversal_cost (for example to 5.0 or higher) so the planner penalizes high-cost cells near obstacles more strongly, or increase the costmap inflation radius. Note that inflated costs do not block line-of-sight; only lethal cells do.