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CEL AI Navigation

Introduction

celNavigationTools it's part of celtool that makes a bunch of useful operations for navigation.

You need to choose Navigator - entity with pcmesh and tracked Target - vector, other entity or map mode.

Then information is returned to celNavigationInfo or choosed variables in blxml:

  • bool success - if everything is ok, entity exists, target exist etc.
  • bool visible - if target is visible
  • float distance - distance between navigator and target
  • vector3 angle - angle between navigator and target (note it's angle between point-point in worldspace, it omits direction vectors)

Simplest case : quite dumb car

  • Determine track by placing nodes on the map. Name that objects for example "waypoint1" "waypoint2" etc. Usualy the best way to do this is making spline/bezier and automatically duplicate nodes on this.
  • Make in your level loader creating trigger for every node.
  • In every AI loop step (1/10s for example) set Navigator to car entity, and target to map node "waypoint"+waypoint_nr and check what celNavigationInfo says.
  • Moving - if distance is far than car can move fast. If distance is close and speed too high then use brakes.
  • Steering - for this we need to know final_angle between car direction and target position (vector-point). Note that angle it's point-point.

final_angle = celNavigationInfo::angle.y - car_rotation

Usually car_rotation should be mirrored BUT in CEL 1.0 camera and then pcactormove, pcwheeled and pchover are mirrored already, then don't do this.

After this operation also is nice to fix angles:

if final_angle >= PI then final_angle -= 2*PI if final_angle < PI then final_angle += 2*PI

Right side it's angle from 0 .. -PI and left 0 .. PI. Now we know where to steer:

if final_angle < -0.1 then SteerRight else iffinal_angle > 0.1 then SteerLeft else if SteerStraight

  • If car will reach waypoint trigger, then increase waypoint_nr.
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