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Rotate vector 90 degrees to the right

Started by smittix Oct 22, 2009 at 11:02 PM 3 replies 20.7k views

Original Post

Oct 22, 2009 at 11:02 PM

Given one normalized 2D vector, how can I get the vector that is rotated 90 degrees to the right about the z-axis? So given a vector of (0, 1), how would I get the vector (1, 0)? I used to know how to do this... something like: Vector2D right = Vector2D(Cos(dirToTarg.y), -Sin(dirToTarg.x)); That's not right but I think it's close..

kdworld

Oct 22, 2009 at 11:40 PM

you can use the following rotation matrix.

x is in radian.. ( radian = degree * Pi / 180; )

[ cos x -sin x ]
[rot] = [ ]
[ sin x cos x ]

multiply your vector with this..

v = v * rot; v is a row vector.

fastcall22

Oct 22, 2009 at 11:49 PM

Quote:

Vector2D right = Vector2D(Cos(dirToTarg.y), -Sin(dirToTarg.x));

Erm, is dirToTarg a pair of angles?

Vector2D right = Vector2D( dirToTarg.y, -dirToTarg.x );

smittix

Oct 23, 2009 at 12:21 AM

Ah.. yeah I think that's what I was looking for _fastcall, thanks. And dirToTarg is the initial vector (1, 0) that I wanted to rotate.

h4tt3n

Oct 23, 2009 at 9:24 AM

Quote:
Original post by bengaltgrsGiven one normalized 2D vector, how can I get the vector that is rotated 90 degrees to the right about the z-axis? So given a vector of (0, 1), how would I get the vector (1, 0)?

I think what you want to find is the normal vector, not to be confused with the normalized vector. A vector normal can point either 90 degrees to the right or left of the original vector. The right-hand normal of vector (x, y) is (y, -x), and the left-hand normal is (-y, x). Plane and simple, no need for trig functions.

Cheers,
Mike

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