ue4 : AI in a space game : relative coordinate : part 1

I will make some articles about AI I am building.
I will not use for the moment, tooling set in ue, because I will not have change of behaviour (attack, defense, patrol).
I will for the moment make only one behaviour, and one goal to reach, without modification depending of the situation of the AI.

My goal is to put in space 2 cubes, and to spawn an AI pawn controlled by an AI controller.
The AI will retrieve first cube, and will fly to this one. It will shoot at it, destroy it, next it will change of target, and fire on the second one.

I ve created a pawn, with a static mesh, with physic enabled.
Don't forget to precise that the pawn is possessed by your specific AIController blueprint:

For my purpose, one of the central need I have, it to be able to orient my pawn to my target.

In AIController,  I ve defined a variable TargetToGo

and create a function to associate a value to the target

I retrieve all object in the scene which are from class gopoint (my cubes, there are two of them). If actual targetToGo is different of the one retrieve in foreach loop, I affect it, and break the loop.
Quite simple.

Ok, for now, I have a target for my pawn... The difficulty is to know how to orient my ship to the target, to move near it, and shoot at it.

Ue4 gives possibilities through transformation tools, to make world location, in local location relative to the ship.

From my pawn, and target, I retrieve static mesh.
From AI ship, I create a transform object (world transform) and I connect it to an inverse transform location object. This last one is the way to make world location into relative location (transform location does the inverse, relative to world).
In parameter, you give actual world location of the target, and you will have a vector in output.




Now, if you break the vector, y which is a left/right coordinate, and z a up/down coordinate. When z and y are at 0, target must be in front of you.
X value in case of y and z at 0 will be the distance to the target.
X can give you clue, if your spaceship is going to, or going away of. If x is equal to - (distance), you are going away from the target.

You have to make rotation, to make x near from distance, and then re apply torque to reduce y and z to 0