2D DEMO

This demo shows the use of the AI system in a non-3D environment and details the methods to move entities around when the AI system cannot move your entities automatically.

This section will detail the AI commands used to construct this demo in the context they are used. For general use of each command you can look them up in the command list section of the help file.

AI Start
AI Set Radius 10.0

The AI Start command creates the AI system and is always called first, the Set Radius command sets the radius for all entities and is usually the second command called. The radius should be set in the main setup code since it can become an expensive operation when many obstacles have already been added.

AI Add Enemy 1,0
AI Set Entity Speed 1,70
AI Set Entity Position 1,entityX, entityY
AI Set Entity Idle Position 1,entityX, entityY

This section creates our single enemy, in this case the entity ID can be any value since we are not linking it with an object and we use this value to refer to the entity from now on. The speed, in this case, is set in pixels per second since that is what we will be using as our units and the AI system will make sure that any movement happens at a speed that is consistent with 70 pixels per second no matter how often AI Update is called. We then set our entity to a position on the screen using a predefined X and Y position, we must also set the position we want the entity to return to when it becomes idle (i.e. Bored) since our entity defaults to automatic mode.

AI Start New Obstacle
AI Add Obstacle Vertex 5,310
AI Add Obstacle Vertex 5,330
AI Add Obstacle Vertex 500,330
AI Add Obstacle Vertex 500,310
AI End New Obstacle 0,1

AI Start New Obstacle
AI Add Obstacle Vertex 140,180
AI Add Obstacle Vertex 140,200
AI Add Obstacle Vertex 635,200
AI Add Obstacle Vertex 635,180
AI End New Obstacle 0,1

rem Boundary
AI Start New Obstacle
AI Add Obstacle Vertex 0,0
AI Add Obstacle Vertex 640,0
AI Add Obstacle Vertex 640,480
AI Add Obstacle Vertex 0,480
AI End New Obstacle 0,1

This section (in the MakeLevel function) creates all our obstacles, since we cannot use AI Add Static Obstacle when not using DarkBasic objects. The first two create the two long walls in the middle of the demo, in a clockwise direction for obstacles, and the third creates a boundary which surrounds the visible area, in an anti-clockwise direction, to prevent the entity leaving the screen. Remember the AI system is still using an X, Z system so the co-ordinates should be specified in clockwise as if looking down on to the X, Z axes even though we are using a 2D co-ordinate system.

For example, the first obstacles uses the corners (5,310) (5,330) (500,330) (500,310) in that order. If we were to draw that on the screen taking the co-ordinates as X,Y values (where 0,0 is in the top left corner) we would be drawing in an anti-clockwise direction:

But from the AI's point of view it is being defined in X,Z co-ordinates (where 0,0 is in the centre of the screen) in which case we are drawing in a clockwise direction:

It is the AI's point of view which is important, and which ultimately defines whether the obstacle is a boundary or localized obstacle so always order your points as if you are drawing in the X,Z system no matter how it may appear in your co-ordinate system.

The third obstacle in the list is the boundary which prevents the entity leaving the screen, so is specified in an anti-clockwise direction (in X,Z co-ordinates) effectively making everything 'behind' it one big obstacle.

At this point the AI setup is complete and we enter our main loop where we call AI Update to start updating our system. These commands are included in our main loop.

entityX = int( AI Get Entity X(1) )
entityY = int( AI Get Entity Z(1) )
angle# = AI Get Entity Angle Y(1)

if mouseclick()=1 then AI Entity Go To Position 1,mousex(),mousey()

AI Update

The first three commands get the updated position and angle of the entity so that it can be drawn to the screen, the entity position is updated after every call to AI Update and since we are not using DarkBasic objects we need to position the entity ourselves. The next command sets a new destination for the entity when the mouse is clicked, the entity will then begin moving towards the destination, wait a while, then move back to its idle position.