OpenEuphoria

Re: rotateing

• Posted by Tommy Carlier <tommy.carlier at telenet.be> Mar 02, 2005
• 487 views

Hayden McKay wrote:
> I'm looking for formulars to rotate 2d and 3d points arround an objects centre
> (x,y) (x,y,z) respectively.
> 
> I've tried:
>             deg/=100
>             new_x=(cos(deg)*x)-(sin(deg)*y)
>             new_y=(sin(deg)*x)+(cos(deg)*y)
> 
> seems to rotate O.K. but it's not what I'm looking for.
> ie: the origen here is assumed to be at 0:0.
> 
> could some please point me in the right direction.

To rotate around a point, just subtract the coordinates from {x, y}
before rotating, and add it again after rotating.

integer origin_x, origin_y, x, y, new_x, new_y
atom deg
...
deg /= 100
new_x = cos(deg) * (x - origin_x) - sin(deg) * (y - origin_y) + origin_x
new_y = sin(deg) * (x - origin_x) + cos(deg) * (y - origin_y) + origin_y

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