Toward More Realistic Pathfinding. Authored by: Marco Pinter. Path finding. How do people find paths? Local knowledge Go downhill Follow the person in front of you Follow the scent of food Global knowledge Consider all possible paths from start to goal
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Authored by: Marco Pinter
Uniform-cost search explored the node that was the closest
What if we knew something about the remaining distance to the goal?
No other optimal algorithm is guaranteed to expand fewer nodes than A*
Can just associate a cost with each turn, but that does not solve the problem entirely. A better smoothing process is to remove as many waypoints as possible.
checkPoint = starting point of pathcurrentPoint = next point in pathwhile (currentPoint->next != NULL) if Walkable(checkPoint, currentPoint->next) // Make a straight path between those points: temp = currentPoint currentPoint = currentPoint->next delete temp from the path else checkPoint = currentPoint currentPoint = currentPoint->next
Checks path from waypoint to waypoint. If the path traveled intersects a blocked location, the waypoint is not removed. Otherwise, remove the waypoint.
Leaves “impossible” sections as is.
Want to be aware of a unit’s turning radius and choose shortest route to destination, in this case the right turn will lead to the shortest route.
Several Postprocess Solutions (cheats)
Sometimes the only legal path that does not violate the turning radius constraints is completely different from the path that the standard A* algorithm produces. To get around this, Pinter proposes a modification known as Directional A*.
First things first
Directional A* does not go directly from a to c because it sees that an abrupt left turn would cause the unit to hit blocked tiles. Thus, waypoint b is found as the shortest legal path.
Problem: adding an end orientation
Nicholas L. Johnson
School of InformationUniversity of Michigan
David C. Brogan
Computer Science DepartmentUniversity of Virginia
Helbing et al. – Escape Panic
Helbing et al. – Trails
Limit on turning radius
Limit on radius Inertia