CODEWITHSUNDEEP
c#xnarotationartificial-intelligence
QuantumArchi
QuantumArchi

Reputation: 73

rotation and radians in XNA, Enemy Ai corrections

ive been having trouble with my mob AI

it works to a point, except it does the opposite of what i want, meaning it turns 180Degrees in the wrong direction 

        Target = playerST.Posistion;
        Vector2 trivial;
        trivial.X = Posistion.X - Target.X;
        trivial.Y = Posistion.Y - Target.Y;
        instant = ((float)Math.Atan2(trivial.Y, trivial.X)) + 3.141592f;

this tells me where my target is and calculates the numbers i need to rotate to

its in radians the plus 3.1etc is like 180 degrees, as calculating it this way gives me either a minumum of -3.141 or a maximum of 3.141 but the rotations of the enemy is done in 0 to 6.28 adding the 3.141 makes instant = in the range of the enemies rotation instead of under it by 3.141

anyway this is the part i get stuck at... the actual rotation 

        // irrelevant
                if (attack == true)
            {

                Vector2 modelVelocityAdd = Vector2.Zero;

                modelVelocityAdd.Y = -(float)Math.Sin(rotation);
                modelVelocityAdd.X = -(float)Math.Cos(rotation);

                modelVelocityAdd *= (0.00002f * speed);
                if ((((rotation) + 0.2f)) < instant && (rotation - 0.2f) > instant)
                {
                    modelVelocity += modelVelocityAdd;
                }
        // not so irrelvant and needs fixing!
                if (instant < rotation )
                    {
                         rotation -= rotationspeed / 2000;
                    }
                else if (rotation < instant)
                    {
                         rotation += rotationspeed / 2000;
                    }

so my problem is how do i stop it from rotating 180 degrees in the wrong direction and actually get it to face the player instead of facing the exact opposite

i cant simply,do what is below because the ship gets trapped and goes back and forth between say 5 degrees and minus 5 degrees

            if (instant < rotation )
                    {
                         rotation += rotationspeed / 2000;
                    }
                else if (rotation < instant)
                    {
                         rotation -= rotationspeed / 2000;
                    }

thanks for any help

Upvotes: 0

Views: 1184

Answers (2)

QuantumArchi
QuantumArchi

Reputation: 73

i figured it out, 

    trivial.X = Posistion.X - Target.X;
    trivial.Y = Posistion.Y - Target.Y;

are wrong it need to be 

    trivial.X = Target.X -Posistion.X  ;
        trivial.Y = Target.Y - Posistion.Y ;

thank you without your help i never would of noticed :D

Upvotes: 0

Hannesh
Hannesh

Reputation: 7488

Instead of

           if (instant < rotation )
                {
                     rotation += rotationspeed / 2000;
                }
            else if (rotation < instant)
                {
                     rotation -= rotationspeed / 2000;
                }

try

rotation = Math.Lerp(rotation, instant, 0.1);

The 0.1 controls the rotation "speed". Using lerp makes the movement more natrual and will fix the problem of the angle oscillating between positive and negative.

Upvotes: 1

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