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what is the formula for Predictive aim ?

  • hi

    i can not use turret behavior so i made my own turret system ...

    but i need for Predictive aim system

    what is the formula ?

    i have variables like :

    • projectile speed
    • turret and target position and angle

    and i know my target moving or not

    ...

    thanks

  • Hope this helps:

    function aimAngle(target, bulletSpeed) {
        var rCrossV = target.x * target.vy - target.y * target.vx;
        var magR = Math.sqrt(target.x*target.x + target.y*target.y);
        var angleAdjust = Math.asin(rCrossV / (bulletSpeed * magR));
    
        return angleAdjust + Math.atan2(target.y, target.x);
    }[/code:ypau5ukx]
    
    At this link is an even more detailed formula:
    [url=http://www.reddit.com/r/gamedev/comments/16ceki/turret_aiming_formula/c7vbu2j]http://www.reddit.com/r/gamedev/comment ... la/c7vbu2j[/url]
  • Hope this helps:

    function aimAngle(target, bulletSpeed) {
        var rCrossV = target.x * target.vy - target.y * target.vx;
        var magR = Math.sqrt(target.x*target.x + target.y*target.y);
        var angleAdjust = Math.asin(rCrossV / (bulletSpeed * magR));
    
        return angleAdjust + Math.atan2(target.y, target.x);
    }[/code:1lcl92kw]
    

    thanks ..

    but what is "target.vy and target.vx" ?

    and construct 2 dont have atan2 ... (i think i must use "angle" but how ?!)

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  • I edited my post above with an formula that is language independent, I just googled the formula for you

  • I edited my post above with an formula that is language independent, I just googled the formula for you

    thanks .. but i know that .. i whant the formula in construct 2 ...

    if anyone can change the formula to construct 2 please do it .. ?

  • It seems to be (i'm not sure):

    target.vy = y-coordinate of target after 1 frame (minimal game graphic update)

    magR = distance beetween turret and target.

  • Vx and vy are the x and y velocities of the target.

    Instead of atan2(y,x) you can use angle(0,0,x,y)

  • Vx and vy are the x and y velocities of the target.

    Instead of atan2(y,x) you can use angle(0,0,x,y)

    how do i calculate Vx and vy ?

    i still looking for formula ...

  • Depending on what movement behavior the target uses they can have an expresion to get velocityX and velocityY, or Speed and angleOfMotion. You can convert the latter to vx,vy with:

    vx = speed * cos(angleOfMotion)

    vy = speed * sin(angleOfMotion)

  • R0J0hound trying to get predictive aim working, but it's not...what am I doing wrong?

    https://dl.dropboxusercontent.com/u/362 ... t_aim.capx

  • jobel The original formula given here is assuming the turret is situated at (0, 0), so you need a modified formula that takes into account the turret's position. Here's a modified formula:

    function aimAngle(turret, target, bulletSpeed) {
        var adjustedX = target.x - turret.x;
        var adjustedY = target.y - turret.y;
        var rCrossV = adjustedX * target.vy - adjustedY * target.vx;
        var magR = Math.sqrt(adjustedX^2 + adjustedY^2);
        var angleAdjust = Math.asin(rCrossV / (bulletSpeed * magR));
    
        return angleAdjust + Angle(turret.x, turret.y, target.x, target.y);
    }
    
    NOTE: adjustedX^2 == adjustedX * adjustedX, ^ is the power operator.[/code:29wly5il]
  • linkman2004 ahh very nice.. works like a charm!

    thanks, I needed this formula and I couldn't use the turret behavior for what I am doing... thanks again!

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