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How to have a Sprite follow the player?


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#1 XwingVmanX   Members   -  Reputation: 108

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Posted 07 August 2012 - 11:53 AM

I was trying to figure out how to make a sprite always look at the players current position. My problem is I am not sure how to check which way the sprite is facing in relation to the players position and adjust him accordingly. I would be grateful if I could get any suggestions as to how to start approaching this.

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#2 Andy474   Members   -  Reputation: 690

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Posted 07 August 2012 - 12:08 PM

Trig :) sohcahtoa or whatever you where tought, and you can find the angle between the sprite and your player, then just rotate it.

E.g. [Badly done picture]
Posted Image
excuse the math ... might not be right, been ages since i done somthing like this :P

#3 XwingVmanX   Members   -  Reputation: 108

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Posted 07 August 2012 - 12:24 PM

OOOOH, Wow all that math is coming back to me. Thanks lol

#4 PunCrathod   Members   -  Reputation: 338

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Posted 07 August 2012 - 02:32 PM

I'll assume you are using c# and XNA. You should use Math.atan2(x2-x1,y2-y1) instead of atan(dx/dy) so you don't have to worry about special case dy=0 and don't have to find wich side the target is. Also what I like to use in cases like these I like to use the following code.
targetangle=Math.Atan2(target.x-this.x,target.y-this.y)//get the angle to the target

turnangle=targetangle-currentangle;//get the difference between the current angle and the target angle

if(turnangle>2*Math.PI)//make sure to wrap the angle between 0 and 2PI
    turnangle-=2*Math.PI
if(turnangle<0)
    turnagnel+=2*Math.PI

if(turnangle<Math.PI&&turnangle>Deadzone){//Check wich side you should turn to get to your target.
    turnright();
}
else if(turnangle>Math.PI&&turnangle<(2*Math.PI)-Deadzone)
{
    turnleft();
}

This should always turn to the direction that is closer to the target. Deadzone is the amount of radians(you get radians from degrees with degrees/360*(2*PI)) the seeker can be off course before it starts to correct its course and should always be between 0 and PI radians(0 and 180 degrees) for this to work correctly.
If there are any errors in the code or elsewhere I blame the late hours.

Edited by PunCrathod, 07 August 2012 - 02:45 PM.





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