Calculate the angle from velocity?

Math and Physics Programming

Started by digital_phantom August 12, 2006 03:27 PM

3 comments, last by digital_phantom 17 years, 8 months ago

126

Author

August 12, 2006 03:27 PM

Is it possible to calculate the angle from the velocity? I already know how to get the speed from the velocity by calculating the magnitude sqr(x * x + y * y), so all I need to know know is how to get the angle.

digital_phantom

126

Author

August 12, 2006 03:41 PM

And in actual code or in english?

haphazardlynamed

340

August 12, 2006 03:41 PM

Angle between vectors formula:

u · v = |u||v| cos θ

where u and v are the vectors, and θ is the angle between them.

|u| means magnitude of vector u
and u · v is a dot product, not a multiplication

DaBono

1,500

August 12, 2006 03:46 PM

What hmmz said. In code:

atan2( y, x );

Or if your language does not specify atan2:

if( x != 0 )   angle = atan( y / x );else   angle = ( y < 0 ? -M_PI : M_PI );

EDIT: Oops, too late to see hmmz second post! [smile]

digital_phantom

126

Author

August 12, 2006 11:45 PM

Thanks everyone,

actually my language doesn't specify atan2 (using VB6).

The whole 'angle = ( y < 0 ? -M_PI : M_PI );' doesn't work currectly when x is zero.

when x is zero, instead of heading down, the angle returns as heading to the left.

What actually works is this: angle = ( y < 0 ? PI * 1.5 : 0 );