PATROLLING DEMO

This demo shows the use of paths to create a patrol route for one or more entities, in this case two paths are created and two entities are assigned to each path. The two paths are created with the same points but in opposite directions, making entities patrol both clockwise and anti-clockwise around the level. This also demonstrates entities avoiding each other when they meet and how they cope with overcrowded destinations.

This document will describe the main AI commands used to create and control this demo in the context they are used. This demo starts very similar to the Path Finding demo so obstacle creation will not be covered here. It is advised you familiarise yourself with the path finding demo first to see how obstacles are setup.

AI Make Path 1
AI Path Add Point 1,40,40
AI Path Add Point 1,40,-40
AI Path Add Point 1,-40,-40
AI Path Add Point 1,-40,40

AI Make Path 2
AI Path Add Point 2,-40,40
AI Path Add Point 2,-40,-40
AI Path Add Point 2,40,-40
AI Path Add Point 2,40,40

After the obstacle setup we come to creating the two paths we want to use. The first is the clockwise path (path 1), starting in the top right hand corner, and the second (path 2) is the anti-clockwise path starting in the top left hand corner. We will refer to these later when we assign them to the entities.

for i = 2 to 5

make object cone i,5
xrotate object i,90
fix object pivot i
position object i,i*5 – 30,2.5,40

AI Add Enemy i,1
AI Set Entity Speed i,10.0

next i

AI Entity Assign Patrol Path 2,2
AI Entity Assign Patrol Path 3,2
AI Entity Assign Patrol Path 4,1
AI Entity Assign Patrol Path 5,1

This creates 4 entities (id's 2-5 inclusive) and sets their speed. The second parameter when adding the entities is to set link the entity to its object, this would be set by default anyway but shows the usage of the second parameter. We then get to assign the entities their patrol paths, two to the clockwise path, two to the anti-clockwise path and immediately changes the behaviour of the entity to patrol whenever it would normally go into an idle state. This allows it to perform all the normal actions of an entity such as attacking and moving but be able to return to the patrol when it has nothing else to do. Any changes to the path, for example adding extra points, will take an immediate effect to any entity using it as a path. To remove the patrol state from an entity and return its idle state assign the entity a path with no points, or delete the path that is assigned to the entity.

AI Update
sync

We then call these two commands in the main loop and the entity movement is automatically handled for us. Entities will start at the beginning of their patrol paths and patrol forever, starting at the beginning again when they reach the end.