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# rotation

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uh hi, i am working on a 3d app in vb (yea i know,vb is evil/slow/crappy etc) and i am having a bit of trouble with roation. i am trying to make a function that will rotate a point (x1,y1) around another point(x2,y2) by a number of degrees.. i cant for the life of me work it out (yea i am braindead ). i have managed to find the distance and create a point x degrees from zero the right distance away but i cant find the original angle that i could add,,,, if this doesn''t make any sense at all please say thanks in advance for any help -skinner

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I'm not so clear on what is the exact problem but...

Does p1 rotates about p2?

If so, then:
1. Calculate where p1 should be if the rotation is about the origin.
2. Translate p1 to p2 (p1 + p2).

Ensure all of your rotation calculations are in Radians or all in Degrees as this is an easy way to receive bogus output.

[edited by - citizen3019 on October 22, 2003 3:27:32 PM]

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quote:
Calculate where p1 should be if the rotation is about the origin

that is the bit i am having some trouble with,,,, i think i have to get the existing angle and the distance, then make a point at the same distance at 0 degrees + the original angle + extra Angle but i am having trouble getting the existing angle (i tried using an inverse sine function but weird stuff was happening)..

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quote:
Original post by skinner
i am having trouble getting the existing angle (i tried using an inverse sine function but weird stuff was happening)..

Tell me more about what you are doing?

Don''t forget Radians or degrees you only need one.
Also, check your quadrants.
Which quadrants can your point be in?

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quote:
Original post by citizen3019
quote:
Original post by skinner
i am having trouble getting the existing angle (i tried using an inverse sine function but weird stuff was happening)..

Tell me more about what you are doing?

Don''t forget Radians or degrees you only need one.
Also, check your quadrants.
Which quadrants can your point be in?

hmm you have just given me an idea....

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argh i had my quadrants different for my inverse sin and inverse cos mixed up,,,, argh i feel so stuuupid, so sorry for wasting your time. thanks

-skinner

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Glad it''s working now!

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