# calculate an angle rotation from a direction vector

## calculate an angle rotation from a direction vector

I have a vector representing a direction and I want my character to 'face' that direction. I know how to rotate the character on its z-axis with sio2 using SIOTransform 'rot' vector, but I need an angle for that (0->360 or -180->180 i think). I think i only need the X and Y values from the direction vector since its only rotating around one axis, so that would be a simple 2D operation. I'm thinking of a function that would take 2 vector arguments and return the angle between those 2 vectors.

What's the best way to do this in SIO2? Definitely a beginner question. Any help is appreciated.

What's the best way to do this in SIO2? Definitely a beginner question. Any help is appreciated.

**geekschmoe**- Posts: 14

Join date: 2009-06-22

## Re: calculate an angle rotation from a direction vector

OK so I figured it out. Simple 2D math (but theres no such thing as 'simple' math to me). On the offshoot that someone could be as beginner as me, here's how I calculated it.

- Code:
`player->SIO2transform->rot->z = atan2(directionVector->y, directionVector->x) * 180 / M_PI;`

**geekschmoe**- Posts: 14

Join date: 2009-06-22

## Re: calculate an angle rotation from a direction vector

Hummm maybe more safe to do this:

- Code:

float a = asinf( _v->x / hypotf( _v->x, _v->y ) ) * SIO2_RAD_TO_DEG;

if( _v->y < 0.0f )

{ a += 180.0f; }

else

{ a = 360.0f - a; }

return a;

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**sio2interactive**- Posts: 1526

Join date: 2008-08-26

Age: 36

Location: Shanghai

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