AI

STEERING BASIC

All games need implemet some for of steering, is using to moving the objects around the our word.the first AI that more people implement is Terminator AI. The creature never thing about getting something (health,ammo,armour, etc) only select the more short way to arrive from his enemy. This code is very easy to understand.
Teminator Pseudocode:

IF X.Targer.Position >X.Terminator.Position -----> X.Terminator.Position =X.Terminator.Position +1
IF X.Targer.Position <X.Terminator.Position -----> X.Terminator.Position =X.Terminator.Position -1

IF Y.Targer.Position >Y.Terminator.Position -----> Y.Terminator.Position =Y.Terminator .Position+1
IF Y.Targer.Position <Y.Terminator.Position -----> Y.Terminator.Position =Y.Terminator.Position -1

IF Z.Targer.Position >Z.Terminator.Position -----> Z.Terminator.Position =Z.Terminator.Position +1
IF Z.Targer.Position <Z.Terminator.Position -----> Z.Terminator.Position =Z.Terminator.Position -1

Is very easy implemented the inverse algorithm to evading a enemy, only change the +1 to -1.
Of course is a very primitive system, really is very difficult that our creature arrive to anyplace if found some obstacle.

The better solution "STEERING", is using a technique "PATH FOLLOWING" . On an environment 2D-3D the routes to arrive a target can be many. And some can be better that other, because in this route you can find a armor, life, because is the more sort route, etc. Or because it is not dangerous route.

But like the "path following" works, first you need create the paths, each map for separate. A path is compound by origin, a destination and a series of coordinates that indicate the route.Will we usually have an origin and multiple destinations, How we can know that is the best route?. Applying destinations values , this means that I need punctuated each "control point" or destination , in function for example that a door is open , that there are life, ammunition or anything.It is simple, but is possibly that using a graph we will understand more .

Figure 1.

Figure 2.

In the figure 1 ,we can see a origin (Green circle) and a target (Red circle) ,the blue circles are a paths to follow, and the red lines are a paths links.
The figure 2 , is a path table , to walking around the map, we need making a physical connection among the corrects paths, for example to arribe form "a" path to
"w"path we need go by "b,e,d" or "h,e,d" or etc.., but the better route? , how I cand find? ,very easy , your need to give a path value he , and to add all the paths or contol points value, the more littlel value is the correct route.

Figure 3.

Figure 4.

In the figure 3 and 4 you can see an example, I have assigned value 1 to all the paths, but you can optimize this, in function at the distance that needed to arrive from a point to another. In games like UT or Quake you can found in your route a healt or enemy for example, then the better router is change (f igure 5). to select the new route , you need add a new value to the next path , if the event is good a little values , if the event is bad a big value.

Figure 5.