objects direction calculation
Author
Doesn any one know how to do this?
if i have object whit 360 degrees
its postion is x y
and i want it to face x2 y2
so how do i calculate it?
Short answer:
John B
[edited by - JohnBSmall on October 19, 2002 5:55:10 PM]
angle = atan((y2 - y) / (x2 - x)); John B
[edited by - JohnBSmall on October 19, 2002 5:55:10 PM]
Author
quote:Original post by JohnBSmall
Short answer:Post if you want the long answer (ie if you don''t understand the trigonometry behind it)angle = atan((y2 - y) / (x2 - x));
John B
[edited by - JohnBSmall on October 19, 2002 5:55:10 PM]
nope im afraid i dont know about it. that atan returns shometing like 1.383852
so what do i do whit that value?
the atan returns a radiant
convert it to normal degrees
180°==PI
degree*PI/180->radiant
radiant*180/PI->degree
convert it to normal degrees
180°==PI
degree*PI/180->radiant
radiant*180/PI->degree
.
Author
This code doesnt work:
double radiant = atan(( (des_y - y) / (des_x - x) ));int direction = (radiant * 180 / PI); // 0 - 360 that gives me really wierd direction, what did i do wrong?
It gives you the angular difference between the two orientations. If you just want a new angle, use atan(des_y/des_x).
And; the answer will be between 0 and 180 (or 90 and 270?), not 0 and 360. Add 180 if des_y is negative (unless I''m wrong, of course.)
And; the answer will be between 0 and 180 (or 90 and 270?), not 0 and 360. Add 180 if des_y is negative (unless I''m wrong, of course.)
The range of tan-1 will be the same as the [periodic] domain of tan. Thus, tan-1 will return a value between -PI/2 and PI/2. However, since the quotient of two negative numbers has the same sign as the quotient of two positive numbers (and +/- has the same sign as -/+), you still have to determine whether the result could simply be a reference angle, and that the object could really be in quadrant 2 or 3.
[edited by - Zipster on October 22, 2002 7:00:29 PM]
[edited by - Zipster on October 22, 2002 7:00:29 PM]
float ToAngle(float x, float y){ if (x == 0) { if (y == 0) return .0f; else if (y > 0) return PI/2; else return PI*3/2; } else if (x > 0) { return atanf(y/x); } else return PI+atanf(y/x);} I'm surprised that noone caught the divide-by-zero possibilities.
Pass this function (x2 - x, y2 - y) for your purposes.
This returns angle in radians, 0 if the angle is undefined (x=0 and y=0)
To go to degrees, multiply the return value by 57.2958 (that's short for 180/PI)
[edited by - Nypyren on October 22, 2002 11:23:40 PM]
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